Microsoft's floating-point to_chars powered by Ryu and Ryu Printf

[Mordante]

Summary

Microsoft would like to contribute its implementation of floating-point to_chars to libc++. This uses the impossibly fast Ryu and Ryu Printf algorithms invented by Ulf Adams at Google. Upstream repos: https://github.com/microsoft/STL and https://github.com/ulfjack/ryu .

Licensing notes: MSVC's STL is available under the Apache License v2.0 with LLVM Exception, intentionally chosen to match libc++. We've used Ryu under the Boost Software License.

This patch contains minor changes from Jorg Brown at Google, to adapt the code to libc++. He verified that it works in Google's Linux-based environment, but then I applied more changes on top of his, so any compiler errors are my fault. (I haven't tried to build and test libc++ yet.) Please tell me if we need to do anything else in order to follow https://llvm.org/docs/DeveloperPolicy.html#attribution-of-changes .

Notes:

• libc++'s integer charconv is unchanged (except for a small refactoring). MSVC's integer charconv hasn't been tuned for performance yet, so you're not missing anything.
• Floating-point from_chars isn't part of this patch because Jorg found that MSVC's implementation (derived from our CRT's strtod) was slower than Abseil's. If you're unable to use Abseil or another implementation due to licensing or technical considerations, Microsoft would be delighted if you used MSVC's from_chars (and you can just take it, or ask us to provide a patch like this). Ulf is also working on a novel algorithm for from_chars.
• This assumes that float is IEEE 32-bit, double is IEEE 64-bit, and long double is also IEEE 64-bit.
• I have added MSVC's charconv tests (the whole thing: integer/floating from_chars/to_chars), but haven't adapted them to libcxx's harness at all. (These tests will be available in the microsoft/STL repo soon.)
• Jorg added int128 codepaths. These were originally present in upstream Ryu, and I removed them from microsoft/STL purely for performance reasons (MSVC doesn't support int128; Clang on Windows does, but I found that x64 intrinsics were slightly faster).
• The implementation is split into 3 headers. In MSVC's STL, charconv contains only Microsoft-written code. xcharconv_ryu.h contains code derived from Ryu (with significant modifications and additions). xcharconv_ryu_tables.h contains Ryu's large lookup tables (they were sufficiently large to make editing inconvenient, hence the separate file). The xmeow.h convention is MSVC's for internal headers; you may wish to rename them.
• You should consider separately compiling the lookup tables (see https://github.com/microsoft/STL/issues/172 ) for compiler throughput and reduced object file size.
• See https://github.com/StephanTLavavej/llvm-project/commits/charconv for fine-grained history. (If necessary, I can perform some rebase surgery to show you what Jorg changed relative to the microsoft/STL repo; currently that's all fused into the first commit.)

Questions:

1. MSVC's STL conventionally uses _Single_uppercase_ugly identifiers, but xcharconv_ryu.h (and tables) also use __double_lowercase_ugly in Ryu-derived code, for ease of search-and-replacing (and comparing) with upstream Ryu. (That file still uses _Single_uppercase_ugly for additions; it looks weird but helped me keep track of what surgery I was performing.) I've compared these files against MSVC's and the diffs are very readable, so I'd like to keep the identifiers following the same convention so our codebases don't diverge too much. Does libc++ want to use __double_lowercase_ugly identifiers? (But apparently you use _Single_uppercase_ugly for template parameters?) If so, I can change the identifiers in this patch, and in microsoft/STL charconv upstream.
2. I have included Microsoft's Apache+LLVM and Ulf's Boost banners, as they have appeared in the microsoft/STL repo. Would you like something different?

[Mordante]

Initial part of moving the code to the dylib instead of headers.
This is just to get feedback from the CI, more changes are still required.

[Mordante]

Mark functions as _LIBCPP_FUNC_VIS, to test whether it fixes the CI.

[Mordante]

Update the X86_64 abi list. This will still fail on Mac.

[Mordante]

Improve placement of internal headers, attempts to fix some build issues.
Adds Mac ABI list updates.

[STL_MSFT]

libcxx/include/__charconv/ryu.h

63 ↗

(On Diff #369315)

@Mordante

The git repo you mentioned is that the public MSVC STL repo at GitHub?

No - the microsoft/STL repo contains the final result of my transformations to Ulf's original code, but it doesn't record how I transformed it (which happened shortly before we went open-source). https://github.com/StephanTLavavej/ryu/commits/msvc-2019.04.29 is what I was referring to. This is not intended to be an alternative to ulfjack/ryu, nor can it be compiled as-is - it simply has a sequence of commits that transforms the code into the final result for charconv. This allowed me to digest changes from upstream by rebasing. (As the date indicates, I haven't touched this in over 2 years. Later changes to charconv haven't been applied back to this repo.)

[ldionne]

libcxx/include/charconv

1671

Let's not make those noexcept as an extension just yet. That will give us more leeway to change it in the future.

1698

It should be possible to move these _Floating_to_chars functions to the dylib as well. In fact, I think what I'd do is move the definition of to_chars itself to the dylib, so that it's the only thing that needs to remain ABI stable. We know that won't change, since it's part of the spec.

[Mordante]

libcxx/include/__charconv/ryu.h

63 ↗

(On Diff #369315)

Thanks!

libcxx/include/charconv

1698

I agree more can be moved to the dylib. I just wanted to move a small part to see whether it works without issues, before moving everything. Especially since after moving some of the "decoration macros" need to be removed. Unfortunately it seems the move ran into some issues with [[no_unique_address]] with clang-cl. I posted a message in Discord about it last weekend.

[Mordante]

Test using _LIBCPP_NO_UNIQUE_ADDRESS instead of [[no_unique_address].
The previous build on the Windows nodes failed due to the lack of support for this attribute.
If this fixes the issue the patch will get its own review, but this is the easiest test-case.

[Mordante]

Update generated files to the new style.

[Mordante]

Add an include path to attempt to fix the build. Some builds already have src directory others not. Not sure why.

[Mordante]

Move more functions to the dylib.

Most importantly the user visible to_chars functions are moved to the dylib.
This allows most of the new header-only code to be moved to the dylib.
That will be done later if the CI passes.
This change makes the functions not available on Apple.

Mainly a test to see whether the CI still passes before moving on.

[Mordante]

Move the entire to_char floating-point implementation to the dylib
Replaced _Bit_cast with std::bit_cast
Updated the ABI list, the Apple lists manually
Basic test to see whether the CI is happy, the last run ran into an ICE in Clang.

[jorgbrown]

In D70631#3068541, @Mordante wrote:

Move the entire to_char floating-point implementation to the dylib

Great to see more stuff moving to the library!

Replaced _Bit_cast with std::bit_cast

Umm, not sure that's a good idea... std::bit_cast is c++20 whereas std::to_chars is c++17.

[Mordante]

Fixes missing include that were removed in a previous iteration.

[Mordante]

In D70631#3068686, @jorgbrown wrote:

In D70631#3068541, @Mordante wrote:

Replaced _Bit_cast with std::bit_cast

Umm, not sure that's a good idea... std::bit_cast is c++20 whereas std::to_chars is c++17.

std::bit_cast is indeed C++20. This is safe since the dylib is always compiled in C++20 mode.

[Mordante]

Remove the no_unique_address part from this patch.

[Mordante]

Rebased
Removed no longer needed includes in <charconv>
Removed const from the public interface to match the Standard
Remove unneeded exported functions, manually adjusted ABI lists
Added _LIBCPP_HIDE_FROM_ABI
Minor polishing

[Mordante]

Fix an error in the ABI list.

[Mordante]

libcxx/include/charconv

605

After moving the implementation to the dylib this reason isn't convincing anymore ;-)
I still prefer to not make the code available prior to C++17 since that's our current policy.

@ldionne agreed or do you feel we should make this available in earlier versions?

libcxx/src/CMakeLists.txt

2

@ldionne This seems to be required since not all build do this automatically.
Should I make this a separate commit?

[h-vetinari]

libcxx/docs/Status/Cxx17.rst

43

I was under the impression that https://reviews.llvm.org/rG87c016078ad72c46505461e4ff8bfa04819fe7ba did most of the work for from_chars?

libcxx/src/ryu/README.txt

8

[Mordante]

libcxx/docs/Status/Cxx17.rst

43

Thanks for both links I wasn't aware of this effort!
At the moment I'm too busy with <format> to look at from_chars, but this is useful when somebody starts working on from_chars.
(I might look at it when I finished the larger projects I'm working on.)

[ldionne]

libcxx/include/charconv

605

I still think it should be available in C++17 and later only, to follow our policy.

libcxx/src/CMakeLists.txt

2

Yes, I believe this should be a separate commit. We also probably want to target_include_directories with cxx_shared and cxx_static instead of using include_directories globally.

[floam]

The C++17 limitation sure seems hard to justify.

[Mordante]

In D70631#3111085, @floam wrote:

The C++17 limitation sure seems hard to justify.

Since this is added to the Standard for C++17 and our current policy is not to backport features it will be limited to C++17 and later.
After moving the code to the dylib the reason stated for only enabling it in C++17 is just no longer the proper reason.

Enabling it for earlier versions may haunt us later. Maybe a paper will be written "Add constexpr Modifiers to Functions to_chars and from_chars for Floating-point Types in <charconv> Header"

[mclow.lists]

In D70631#3112196, @Mordante wrote:

In D70631#3111085, @floam wrote:

The C++17 limitation sure seems hard to justify.

Since this is added to the Standard for C++17 and our current policy is not to backport features it will be limited to C++17 and later.
After moving the code to the dylib the reason stated for only enabling it in C++17 is just no longer the proper reason.

The reason the integral bits of to_chars was enabled in C++11 and later was to reuse the code in to_string.

[Mordante]

Recently the CI has been updated to ToT, rebased to see the current build status.
Addresses a few minor review comments.

[Mordante]

Thanks for sharing the motivation for enabling integral version of to_chars in C++11 @mclow.lists.

libcxx/src/CMakeLists.txt

2

It should indeed be target_include_directories, however for an initial test using the global version is much easier. For now I keep it in this patch. Once all is green I'll move this to its own patch.

[h-vetinari]

libcxx/src/ryu/README.txt

8

Not sure if this comment is properly visible (not much experience on Phabricator), but this should be "by Microsoft for inclusion" instead of "by Microft for includion"

[Mordante]

Fix GCC CI build.

[Mordante]

libcxx/src/ryu/README.txt

8

Thanks for the ping. It's visible and indeed not done yet, that's why the items isn't marked as done yet. Yesterday I wanted to get the CI done before I left. Once the CI is green I want to address all open issues and start to get the patch ready for review.

[Mordante]

Attempt to fix some CI issues. The bootstrapping build will probably still fail.

[Mordante]

Rebased and attempt to fix the CI.

[Mordante]

Disable test on AIX for now.

[Mordante]

libcxx/src/include/ryu/d2fixed.h

54

@ldionne Do you have an idea what's wrong here. I declare this function here and define it in src/ryu/d2fixed.cpp. Do you see anything wrong with this? Am I missing some visibility macro's?

The reason I ask is since this cause causes a ICE in Clang when building with -DCMAKE_BUILD_TYPE=RelWithDebInfo -DLLVM_ENABLE_ASSERTIONS=ON. This combination is used on our CI's bootstrap build.

[ldionne]

libcxx/src/include/ryu/d2fixed.h

54

Is this supposed to be exported from the dylib? If so, it needs _LIBCPP_FUNC_VIS IIRC. Otherwise, no visibility macro should be fine (it will automatically be hidden since we build the dylib with -fvisibility=hidden, which you should be able to confirm by looking at the build log).

I think the best course of action here would be to reduce the Clang ICE, since an ICE is always a bug.

[Mordante]

libcxx/src/include/ryu/d2fixed.h

54

It's supposed to be hidden in the dylib. This is part of the functions that we want to hide to allow us to change the implementation of the floating point algorithm without introducing ABI breaks. The dylib is indeed build with -fvisibility=hidden.

I agree and ICE is a bug and I want to report it after reducing it. For now I wanted to make sure I didn't overlook anything obvious. Thanks for your input.

[Mordante]

libcxx/include/charconv

117

Since std::to_chars and std::to_string are both in the dylib this isn't an issue anymore.

libcxx/src/include/ryu/d2fixed.h

54

Is this supposed to be exported from the dylib? If so, it needs _LIBCPP_FUNC_VIS IIRC. Otherwise, no visibility macro should be fine (it will automatically be hidden since we build the dylib with -fvisibility=hidden, which you should be able to confirm by looking at the build log).

I think the best course of action here would be to reduce the Clang ICE, since an ICE is always a bug.

Reduced and reported as https://bugs.llvm.org/show_bug.cgi?id=52584

libcxx/test/std/utilities/charconv/charconv.msvc/double_scientific_precision_to_chars_test_cases_1.hpp

40

@STL_MSFT If you're willing to update the headers in Microsoft's that would be great. Then I can sync them.

[Mordante]

Rebased.
Partial update of the tests with MSVC STL, other changes need more effort.
Polishing and addressing review comments.

[ldionne]

LGTM with comments, assuming CI passes. Also, please add a release note.

I want to thank everybody who got involved in shipping this, I'm glad we finally finished this up!

I know there's been some progress on algorithms to implement this in the recent years -- it should always be possible to swap the implementation under the hood since everything is implemented in the dylib, and the ABI boundary is not going to change.

libcxx/CREDITS.TXT

29

@Mordante You might want to credit yourself for the part of the work you did on landing this.

libcxx/include/charconv

611

Since those are libc++'s own declarations, we should use libc++ style and use __first instead of _First. Similarly, let's put _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS on its own line.

Finally, I think we can remove the bit of the license here as long as we retain the one in the source file?

libcxx/lib/abi/CHANGELOG.TXT

49

libcxx/test/std/utilities/charconv/charconv.msvc/test.pass.cpp

12–14

This is technically inaccurate since it hasn't landed yet period, let's change it to my suggestion.

I'll fix it up once it lands in one of our OSes.

22

Do you know why it's failing on AIX? Just curious.

[Mordante]

Attempt to fix the CI.

[Mordante]

Attempt to fix the MinGW build.

[Mordante]

Fix a typo.

[Mordante]

Attempt to fix the failed test on MinGW.

[mstorsjo]

libcxx/src/include/ryu/d2s_intrinsics.h

50

I think you could loosen this into #if defined(_M_X64) && defined(_MSC_VER); _LIBCPP_COMPILER_MSVC is only defined when building with the actual MSVC, not clang-cl impersonating MSVC. (And the real MSVC isn't supported for building libcxx in practice.)

Or did this codepath give errors when built with clang-cl before?

72

Isn't this condition kinda opposite to what you suggest in the comment? I.e. the comment writes (and we discussed) that mingw does support int128, but then you check defined(_M_X64) && !defined(__MINGW32__) - I believe this codepath isn't used here as intended.

Actually, I would suggest simplifying this whole condition into this:

#elif defined(__SIZEOF_INT128__) && ( \
    (defined(__clang__) && !defined(_MSC_VER)) || \
    (defined(__GNUC__) && !defined(__clang__) && !defined(__CUDACC__)))

Thus, if we have __SIZEOF_INT128__ defined (this should exclude all 32 bit targets, so we don't need to check for any 64 bit architecture specifically). This check in itself is almost enough as such. But then as a extra requirement, we'd only try this if we also have specifically clang or gcc. And for clang, we'd exclude building in MSVC mode, where we might not have all the runtime functions available. (If it turns out that the code below doesn't actually generate any calls to runtime helpers, we wouldn't need the check for _MSC_VER at all.)

Or it could even be as simple as this:

#elif !defined(_LIBCPP_HAS_NO_INT128) && !defined(_MSC_VER)

We already have _LIBCPP_HAS_NO_INT128 in libcxx, and it might be good to honor it. However that define is only based on compiler support - in MSVC mode, it doesn't know that we actually don't have all the necessary runtime functions.

We have __uint128 support in clang or gcc or MinGW 64

Those three aren't really three comparable things - when building for mingw, you'd be using either clang or gcc. Maybe "We have __uint128 support in gcc and clang, except when in MSVC mode" (or clang-cl instead of MSVC)?

[Mordante]

In D70631#3149545, @ldionne wrote:

LGTM with comments, assuming CI passes. Also, please add a release note.

Good point!

libcxx/CREDITS.TXT

29

Good point. I even discovered I never added myself to the credits.

libcxx/src/include/ryu/d2s_intrinsics.h

50

I only had an issue when the guard was #ifdef _M_X64. I'll apply your suggestion and let the CI be the judge.

72

I've changed it to your first suggestion, that matches the original code better. I could use _LIBCPP_HAS_NO_INT128 but that's defined in terms of __SIZEOF_INT128__. I prefer to keep this as much to the original code submitted by Microsoft to keep the size of the diff with their code-base as small as possible.

libcxx/test/std/utilities/charconv/charconv.msvc/test.pass.cpp

12–14

Good to know, I wasn't sure what the process was to make sure it's enabled in the next Apple product.

[Mordante]

Rebased and addresses review comments.
I really like to test the dylib changes in the CI.

[phosek]

This broke all our builders that use the bootstrapping build due to PR52584. I saw you disabled the use of debugging information for libc++ ci in 15495be014032339600cda7770d7bf45dfb10d54, but there are other projects that build LLVM from source at HEAD which will be affected by that issue. I'd prefer if this change was reverted until PR52584 is addressed or we find some other workaround.

[phosek]

In D70631#3174380, @phosek wrote:

This broke all our builders that use the bootstrapping build due to PR52584. I saw you disabled the use of debugging information for libc++ ci in 15495be014032339600cda7770d7bf45dfb10d54, but there are other projects that build LLVM from source at HEAD which will be affected by that issue. I'd prefer if this change was reverted until PR52584 is addressed or we find some other workaround.

@ldionne Would it be fine with you if I revert this change? I haven't heard back from @Mordante and libc++ build is still failing all our builders because of Clang ICE that hasn't yet been addressed. We cannot disable the use of debug info because we use it for symbolization, and we don't want to disable assertions because we might then miss other issues.

[ldionne]

In D70631#3175290, @phosek wrote:

In D70631#3174380, @phosek wrote:

This broke all our builders that use the bootstrapping build due to PR52584. I saw you disabled the use of debugging information for libc++ ci in 15495be014032339600cda7770d7bf45dfb10d54, but there are other projects that build LLVM from source at HEAD which will be affected by that issue. I'd prefer if this change was reverted until PR52584 is addressed or we find some other workaround.

@ldionne Would it be fine with you if I revert this change? I haven't heard back from @Mordante and libc++ build is still failing all our builders because of Clang ICE that hasn't yet been addressed. We cannot disable the use of debug info because we use it for symbolization, and we don't want to disable assertions because we might then miss other issues.

Yes, please revert the change. We will investigate tomorrow. I think @Mordante is in a different time zone.

[Mordante]

@phosek Thanks for reverting the patch. I'm in a different timezone and just read your message.

[dblaikie]

libcxx/src/include/to_chars_floating_point.h

120

This bit_cast means the to_chars functionality (intended to be available in C++17 or above) fails when used in a C++17 context, since bit_cast is only available in C++20 onwards - at least in an internal Google build this seems to be the case (possible there's something esoteric there).

Does that seem plausible/a problem that needs fixing upstream here?

[dblaikie]

libcxx/src/include/to_chars_floating_point.h

120

Looking back at some of the review discussion, it looks like this was deemed OK because bit_cast would be available in the dylib even when compiling in an earlier language mode? But the declaration of the function is still gated on C++20 or above here: https://github.com/llvm/llvm-project/blob/572d1ecccc473ba4ddb46dd04759dc2e336f0e1c/libcxx/include/__bit/bit_cast.h#L22 so this usage fails to compile before ever worrying about whether it links correctly.

[STL_MSFT]

libcxx/src/include/to_chars_floating_point.h

120

Good question about upstream - it's unaffected as we used an internal helper _Bit_cast precisely so that we could have access to it in C++17 mode. This is https://github.com/microsoft/STL/blob/3c2fd04d441d46ec9d914d9cbb621a3bac96c3a5/stl/inc/charconv#L2081 and https://github.com/microsoft/STL/blob/3c2fd04d441d46ec9d914d9cbb621a3bac96c3a5/stl/inc/xutility#L62-L74 .

[dblaikie]

libcxx/src/include/to_chars_floating_point.h

120

The code that was committed doesn't appear to use that _Bit_cast internal helper.
The helper and its use seemed to have been removed in this iteration of the proposed patch: https://reviews.llvm.org/D70631?vs=380156&id=380203#toc
The final commited code ( https://reviews.llvm.org/rGa8025e06fc0f2fe1bbee9e1a6f15c336bfbdcb05 ) have no mention of _Bit_cast and use _VSTD::bit_cast in several places, including this one (line 119 here that I'm commenting on).

Am I misunderstanding something?

[floam]

libcxx/src/include/to_chars_floating_point.h

120

@dblaikie They are saying that is how Microsoft solved that quandary in their product.

[STL_MSFT]

libcxx/src/include/to_chars_floating_point.h

120

I think you're completely correct - I was merely clarifying that there is no issue that needs to be fixed upstream here, it was introduced during the later changes here.

[dblaikie]

libcxx/src/include/to_chars_floating_point.h

120

Ah, sorry, I meant "upstream" as in "LLVM" here (as contrasted to "Downstream" being "inside google" - ie: something we need to fix on our end internally).

Sounds like we're on the same page here. Sorry for the confusion.

[Mordante]

libcxx/src/include/to_chars_floating_point.h

120

This header is part of the dylib and not part of a libc++ header shipped to customers.
Since the dylib is always build with C++20 it's safe to use bit_cast here.

The public std::to_chars for floating-point is available in C++17 and newer.
There are lit tests ensuring the function works correctly in C++17, C++20, and C++2b.

[Mordante]

Relanded since the bug blocking it has been resolved.

[dblaikie]

libcxx/src/include/to_chars_floating_point.h

120

Ah, sure, thanks. Yeah, looks like we might be building even the library with std=gnu++17 internally & probably need to fix that. Will look into it on our side.

[ldionne]

Let's not forget to restore Debug information in the bootstrapping build.

[Mordante]

In D70631#3188838, @ldionne wrote:

Let's not forget to restore Debug information in the bootstrapping build.

I already did that after it was clear the bug needed to be resolved before this patch could land.
https://reviews.llvm.org/rGade336dee4762572bbd03085d96ce72bdbbb123b

libcxx/src/include/to_chars_floating_point.h

120

Thanks. I'm surprised this works since the CMake file should force C++20. I expected the format.cpp to require C++20, but it seems that is guarded. (That code was added while we didn't require C++20 yet, but these guards should be removed.)

[dblaikie]

libcxx/src/include/to_chars_floating_point.h

120

The issue is that we don't use CMake internally, but Bazel instead - apparently we've been "getting away" with building in C++17 mode until this change. But that's just a bug on our side to get fixed. Sorry for the noise in the review & thanks for walking me through the issue/pointing out the distinctions here.

[bcain]

This test libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp fails downstream for us w/Hexagon SDK. It's a subtle nit from the compiler regarding format specifiers.

I can post a patch to change the test to use the inttypes.h PRI___ specifiers instead. But it occurs to me: since this is a lit test, are the printouts only used for debugging? Should/could we purge them or hide them behind a debug guard? Does this test come from a third party repository that we want to stay in sync with? The commit regards printf implementation -- are any of the calls to printf part of the intended scope of the test? If not, could/should the test be redesigned to use C++ streams instead?

Apologies for the lack-of-context questions.

Here's the downstream failures btw (both unsigned long and unsigned int are 32-bits on this target):

.../tools/llvm-top/libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp:94:23: error: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Werror,-Wformat]
        printf("%u ", elem);
                ~~    ^~~~
                %lu
.../tools/llvm-top/libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp:569:56: error: format specifies type 'unsigned int' but the argument has type 'uint32_t' (aka 'unsigned long') [-Werror,-Wformat]
        fprintf(stderr, "%s failed for 0x%08X\n", msg, bits);
                                         ~~~~          ^~~~
                                         %08lX
.../tools/llvm-top/libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp:1096:43: error: format specifies type 'unsigned int' but the argument has type 'unsigned long' [-Werror,-Wformat]
    printf("Randomized test cases: %u\n", PrefixesToTest * Fractions);
                                   ~~     ^~~~~~~~~~~~~~~~~~~~~~~~~~
                                   %lu

[STL_MSFT]

In D70631#3337734, @bcain wrote:

This test libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp fails downstream for us w/Hexagon SDK. It's a subtle nit from the compiler regarding format specifiers.

This was my fault, sorry about that - I forgot that uint32_t is slightly platform-dependent.

I can post a patch to change the test to use the inttypes.h PRI___ specifiers instead.

I think that'd be the least invasive fix, yeah.

But it occurs to me: since this is a lit test, are the printouts only used for debugging?

In general, they're needed to understand test failures - particularly the ones that say "this value failed, it's a randomized test, so report this to the maintainers and don't just rerun it".

Does this test come from a third party repository that we want to stay in sync with?

Yes, https://github.com/microsoft/STL . We'd be happy to review and merge a PR there to keep it in sync with libcxx.

The commit regards printf implementation -- are any of the calls to printf part of the intended scope of the test? If not, could/should the test be redesigned to use C++ streams instead?

printf/fprintf isn't essential, we could also use iostreams, but iostreams manipulators (for the equivalent of %016llX) are a pain to remember (even for a Standard Library maintainer, heh) so I used printf for convenience.

(There are sprintf_s calls in the MSVC implementation that verify that to_chars prints floating-point values in the same way - those are essential since we don't want to compare against the iostreams implementation)

[• Quuxplusone]

In D70631#3338720, @STL_MSFT wrote:

In D70631#3337734, @bcain wrote:

I can post a patch to change the test to use the inttypes.h PRI___ specifiers instead.

I think that'd be the least invasive fix, yeah.

FWIW, I would vastly rather see printf("%zu whatever", size_t(x)) instead of printf("%" PRIu32 " whatever", x). Keeps the message's string literal all in one piece, doesn't suffer UDL-related lexer issues, and doesn't require intimate knowledge of <stdint.h> or whatever.

[Mordante]

Yes please provide a patch, can you supply one to libc++ and one to MSVC STL? Thanks.

[bcain]

In D70631#3340840, @Mordante wrote:

Yes please provide a patch, can you supply one to libc++ and one to MSVC STL? Thanks.

I will provide a patch.

It is considerably easier for me to supply it to libc++ because our contributions are permitted there already. I don't think it will be quite so easy to get MSVC STL repo added. But the license is the same, so maybe.

libcxx/CREDITS.TXT

 This file is a partial list of people who have contributed to the LLVM/libc++
 project.  If you have contributed a patch or made some other contribution to
 LLVM/libc++, please submit a patch to this file to add yourself, and it will be
 done!
 
 The list is sorted by surname and formatted to allow easy grepping and
 beautification by scripts.  The fields are: name (N), email (E), web-address
 (W), PGP key ID and fingerprint (P), description (D), and snail-mail address
 (S).
 
 N: Saleem Abdulrasool
 E: [e-mail]
 D: Minor patches and Linux fixes.
 
+N: Ulf Adams
+D: Invented the Ryu and Ryu Printf algorithms used in floating-point to_chars, and wrote the initial code.
+
 N: Muiez Ahmed
 E: [e-mail]
 D: z/OS port.
 
 N: Dan Albert
 E: [e-mail]
 D: Android support and test runner improvements.
 
 N: Dimitry Andric
 E: [e-mail]
 D: Visibility fixes, minor FreeBSD portability patches.
 
 N: Holger Arnold
 E: [e-mail]
 D: Minor fix.
 
+N: Jorg Brown
+D: Ported floating-point to_chars from MSVC to libc++.
+
 N: David Chisnall
 E: theraven at theravensnest dot org
 D: FreeBSD and Solaris ports, libcxxrt support, some atomics work.
 
 N: Marshall Clow
 E: [e-mail]
 E: [e-mail]
 D: C++14 support, patches and bug fixes.

 N: Hyeon-bin Jeong
 E: [e-mail]
 D: Minor patches and bug fixes.
 
 N: Argyrios Kyrtzidis
 E: [e-mail]
 D: Bug fixes.
 
+N: Stephan T. Lavavej
+E: [e-mail]
+E: [e-mail]
+D: Implemented floating-point to_chars.
+
+N: Microsoft Corporation
+D: Contributed floating-point to_chars.
+
 N: Bruce Mitchener, Jr.
 E: [e-mail]
 D: Emscripten-related changes.
 
 N: Michel Morin
 E: [e-mail]
 D: Minor patches to is_convertible.
 

 
 N: Klaas de Vries
 E: klaas at klaasgaaf dot nl
 D: Minor bug fix.
 
 N: Mark de Wever
 E: koraq at xs4all dot nl
 D: Format library support.
+D: Finalized the porting of MSVC's to_chars to libc++.
 
 N: Zhang Xiongpang
 E: [e-mail]
 D: Minor patches and bug fixes.
 
 N: Xing Xue
 E: [e-mail]
 D: AIX port
 
 N: Jeffrey Yasskin
 E: [e-mail]
 E: [e-mail]
 D: Linux fixes.
 
 N: Zhihao Yuan
 E: [e-mail]
 D: Standard compatibility fixes.

libcxx/docs/ReleaseNotes.rst

 - Support for building libc++ on top of a C Standard Library that does not support ``wchar_t`` was
   added. This is useful for building libc++ in an embedded setting, and it adds itself to the various
   freestanding-friendly options provided by libc++.
 
 - ``_LIBCPP_DEBUG`` equals to ``1`` enables the randomization of unspecified
   behavior of standard algorithms (e.g. equal elements in ``std::sort`` or
   randomization of both sides of partition for ``std::nth_element``)
 
+- Floating-point support for ``std::to_chars`` support has been added.
+  Thanks to Stephan T. Lavavej and Microsoft for providing their implemention
+  to libc++.
+
 API Changes
 -----------
 
 - The functions ``std::atomic<T*>::fetch_(add|sub)`` and
   ``std::atomic_fetch_(add|sub)`` no longer accept a function pointer. While
   this is technically an API break, the invalid syntax isn't supported by
   libstc++ and MSVC STL.  See https://godbolt.org/z/49fvzz98d.
 

libcxx/docs/Status/Cxx17.rst

 .. _cxx17-status:
 
 ================================
 libc++ C++17 Status
 ================================
 
 .. include:: ../Helpers/Styles.rst
 
 .. contents::
    :local:

 
 .. csv-table::
    :file: Cxx17Papers.csv
    :header-rows: 1
    :widths: auto
 
 .. note::
 
+   .. [#note-P0067] P0067: ``std::(to|from)_chars`` for integrals has been available since version 7.0. ``std::to_chars`` for ``float`` and ``double`` since version 14.0 ``std::to_chars`` for ``long double`` uses the implementation for ``double``.
    .. [#note-P0607] P0607: The parts of P0607 that are not done are the ``<regex>`` bits.
 
 
 .. _issues-status-cxx17:
 
 Library Working Group Issues Status
 ====================================
 
 .. csv-table::
    :file: Cxx17Issues.csv
    :header-rows: 1
    :widths: auto

libcxx/docs/Status/Cxx17Papers.csv

 "`p0346r1 <https://wg21.link/p0346r1>`__","LWG","A <random> Nomenclature Tweak","Oulu","|Complete|","3.9"
 "`p0358r1 <https://wg21.link/p0358r1>`__","LWG","Fixes for not_fn","Oulu","|Complete|","3.9"
 "`p0371r1 <https://wg21.link/p0371r1>`__","LWG","Temporarily discourage memory_order_consume","Oulu","|Nothing To Do|","n/a"
 "`p0392r0 <https://wg21.link/p0392r0>`__","LWG","Adapting string_view by filesystem paths","Oulu","|Complete|","4.0"
 "`p0393r3 <https://wg21.link/p0393r3>`__","LWG","Making Variant Greater Equal","Oulu","|Complete|","4.0"
 "`P0394r4 <https://wg21.link/P0394r4>`__","LWG","Hotel Parallelifornia: terminate() for Parallel Algorithms Exception Handling","Oulu","",""
 "","","","","",""
 "`P0003R5 <https://wg21.link/P0003R5>`__","LWG","Removing Deprecated Exception Specifications from C++17","Issaquah","|Complete|","5.0"
-"`P0067R5 <https://wg21.link/P0067R5>`__","LWG","Elementary string conversions, revision 5","Issaquah","|Partial|",""
+"`P0067R5 <https://wg21.link/P0067R5>`__","LWG","Elementary string conversions, revision 5","Issaquah","|Partial| [#note-P0067]",""
 "`P0403R1 <https://wg21.link/P0403R1>`__","LWG","Literal suffixes for ``basic_string_view``\ ","Issaquah","|Complete|","4.0"
 "`P0414R2 <https://wg21.link/P0414R2>`__","LWG","Merging shared_ptr changes from Library Fundamentals to C++17","Issaquah","|Complete|","11.0"
 "`P0418R2 <https://wg21.link/P0418R2>`__","LWG","Fail or succeed: there is no atomic lattice","Issaquah","",""
 "`P0426R1 <https://wg21.link/P0426R1>`__","LWG","Constexpr for ``std::char_traits``\ ","Issaquah","|Complete|","4.0"
 "`P0435R1 <https://wg21.link/P0435R1>`__","LWG","Resolving LWG Issues re ``common_type``\ ","Issaquah","|Complete|","4.0"
 "`P0502R0 <https://wg21.link/P0502R0>`__","LWG","Throwing out of a parallel algorithm terminates - but how?","Issaquah","",""
 "`P0503R0 <https://wg21.link/P0503R0>`__","LWG","Correcting library usage of ""literal type""","Issaquah","|Complete|","4.0"
 "`P0504R0 <https://wg21.link/P0504R0>`__","LWG","Revisiting in-place tag types for any/optional/variant","Issaquah","|Complete|","4.0"

libcxx/include/__availability

 #   define _LIBCPP_AVAILABILITY_FILESYSTEM
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM_PUSH
 #   define _LIBCPP_AVAILABILITY_FILESYSTEM_POP
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem
 
     // This controls the availability of std::to_chars.
 #   define _LIBCPP_AVAILABILITY_TO_CHARS
 
+    // This controls the availability of floating-point std::to_chars functions.
+    // These overloads were added later than the integer overloads.
+#   define _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT
+
     // This controls the availability of the C++20 synchronization library,
     // which requires shared library support for various operations
     // (see libcxx/src/atomic.cpp).
 #   define _LIBCPP_AVAILABILITY_SYNC
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_atomic_wait
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_barrier
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_latch
 // #   define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_semaphore
#   if (defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 101500) ||    \
         (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 130000) ||         \
         (defined(__ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_WATCH_OS_VERSION_MIN_REQUIRED__ < 60000)
 #       define _LIBCPP_AVAILABILITY_DISABLE_FTM___cpp_lib_filesystem
 #   endif
 
 #   define _LIBCPP_AVAILABILITY_TO_CHARS                                        \
         _LIBCPP_AVAILABILITY_FILESYSTEM
 
+#   define _LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT                         \
+        __attribute__((unavailable))
+
 #   define _LIBCPP_AVAILABILITY_SYNC                                            \
         __attribute__((availability(macosx,strict,introduced=11.0)))            \
         __attribute__((availability(ios,strict,introduced=14.0)))               \
         __attribute__((availability(tvos,strict,introduced=14.0)))              \
         __attribute__((availability(watchos,strict,introduced=7.0)))
 #   if (defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 110000) ||    \
         (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 140000) || \
         (defined(__ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__) && __ENVIRONMENT_TV_OS_VERSION_MIN_REQUIRED__ < 140000) ||         \

libcxx/include/charconv

 
 #ifndef _LIBCPP_CXX03_LANG
 
 to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
 from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;
 
 namespace __itoa
 {
 
 static _LIBCPP_CONSTEXPR uint64_t __pow10_64[] = {
     UINT64_C(0),
     UINT64_C(10),
     UINT64_C(100),
     UINT64_C(1000),
     UINT64_C(10000),
     UINT64_C(100000),
     UINT64_C(1000000),

 template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
 inline _LIBCPP_INLINE_VISIBILITY from_chars_result
 from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
 {
     _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
     return __from_chars_integral(__first, __last, __value, __base);
 }
 
+// Floating-point implementation starts here.
+// Unlike the other parts of charconv this is only available in C++17 and newer.
+#if _LIBCPP_STD_VER > 14
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, float __value);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, double __value);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, long double __value);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision);
+
+#  endif // _LIBCPP_STD_VER > 14
 #endif // _LIBCPP_CXX03_LANG
 
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
 #endif // _LIBCPP_CHARCONV

libcxx/lib/abi/CHANGELOG.TXT

 `generate-cxx-abilist` target, and look at the diff.
 
 New entries should be added directly below the "Version" header.
 
 ------------
 Version 14.0
 ------------
 
+* [libc++] `to_chars` for floating point.
+
+  This commit added the `to_chars` implementation for floating point values.
+  The entire implementation resides in the dylib and the functions specified
+  in the Standard are now part of the ABI.
+
+  arm64-apple-darwin
+  ------------------
+  Symbol added: _ZNSt3__18to_charsEPcS0_d
+  Symbol added: _ZNSt3__18to_charsEPcS0_dNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_dNS_12chars_formatEi
+  Symbol added: _ZNSt3__18to_charsEPcS0_e
+  Symbol added: _ZNSt3__18to_charsEPcS0_eNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_eNS_12chars_formatEi
+  Symbol added: _ZNSt3__18to_charsEPcS0_f
+  Symbol added: _ZNSt3__18to_charsEPcS0_fNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_fNS_12chars_formatEi
+
+  x86_64-apple-darwin
+  -------------------
+  Symbol added: _ZNSt3__18to_charsEPcS0_d
+  Symbol added: _ZNSt3__18to_charsEPcS0_dNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_dNS_12chars_formatEi
+  Symbol added: _ZNSt3__18to_charsEPcS0_e
+  Symbol added: _ZNSt3__18to_charsEPcS0_eNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_eNS_12chars_formatEi
+  Symbol added: _ZNSt3__18to_charsEPcS0_f
+  Symbol added: _ZNSt3__18to_charsEPcS0_fNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_fNS_12chars_formatEi
+
+  x86_64-unknown-linux-gnu
+  ------------------------
+  Symbol added: _ZNSt3__18to_charsEPcS0_d
+  Symbol added: _ZNSt3__18to_charsEPcS0_dNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_dNS_12chars_formatEi
+  Symbol added: _ZNSt3__18to_charsEPcS0_e
+  Symbol added: _ZNSt3__18to_charsEPcS0_eNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_eNS_12chars_formatEi
+  Symbol added: _ZNSt3__18to_charsEPcS0_f
+  Symbol added: _ZNSt3__18to_charsEPcS0_fNS_12chars_formatE
+  Symbol added: _ZNSt3__18to_charsEPcS0_fNS_12chars_formatEi
+
 * [libc++] Resolve missing table_size symbol
 
   This commit added an out-of-line definition for `table_size` in the library.
   This is not an ABI break since we are just adding a symbol to the library.
   In fact, any program that would have attempted to refer to that symbol would
   have previously failed to link.
 
   x86_64-apple-apple-darwin

libcxx/lib/abi/arm64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist

 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwEC2Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwED0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18time_getIcNS_19istreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__18time_getIwNS_19istreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__18time_putIcNS_19ostreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__18time_putIwNS_19ostreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_d', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_dNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_dNS_12chars_formatEi', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_e', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_eNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_eNS_12chars_formatEi', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_f', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_fNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_fNS_12chars_formatEi', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImE6resizeEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImEC1Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImEC2Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__19__num_getIcE17__stage2_int_loopEciPcRS2_RjcRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSD_S2_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__19__num_getIcE17__stage2_int_prepERNS_8ios_baseEPcRc', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__19__num_getIcE19__stage2_float_loopEcRbRcPcRS4_ccRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSE_RjS4_', 'type': 'FUNC'}

 {'is_defined': True, 'name': '___cxa_vec_delete2', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_delete3', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_dtor', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_new', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_new2', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_new3', 'type': 'I'}
 {'is_defined': True, 'name': '___dynamic_cast', 'type': 'I'}
 {'is_defined': True, 'name': '___gxx_personality_v0', 'type': 'I'}
 No newline at end of file

libcxx/lib/abi/x86_64-apple-darwin.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist

 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwEC2Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwED0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18numpunctIwED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18time_getIcNS_19istreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__18time_getIwNS_19istreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__18time_putIcNS_19ostreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '__ZNSt3__18time_putIwNS_19ostreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 0, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_d', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_dNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_dNS_12chars_formatEi', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_e', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_eNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_eNS_12chars_formatEi', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_f', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_fNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '__ZNSt3__18to_charsEPcS0_fNS_12chars_formatEi', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImE6resizeEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImEC1Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImEC2Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__18valarrayImED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__19__num_getIcE17__stage2_int_loopEciPcRS2_RjcRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSD_S2_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '__ZNSt3__19__num_getIcE17__stage2_int_prepERNS_8ios_baseEPcRc', 'type': 'FUNC'}
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 {'is_defined': True, 'name': '___cxa_vec_delete2', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_delete3', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_dtor', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_new', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_new2', 'type': 'I'}
 {'is_defined': True, 'name': '___cxa_vec_new3', 'type': 'I'}
 {'is_defined': True, 'name': '___dynamic_cast', 'type': 'I'}
 {'is_defined': True, 'name': '___gxx_personality_v0', 'type': 'I'}
 No newline at end of file

libcxx/lib/abi/x86_64-unknown-linux-gnu.libcxxabi.v1.stable.exceptions.no_new_in_libcxx.abilist

 {'is_defined': True, 'name': '_ZNSt3__18numpunctIwEC2Em', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__18numpunctIwED0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__18numpunctIwED1Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__18numpunctIwED2Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__18time_getIcNS_19istreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 16, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZNSt3__18time_getIwNS_19istreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 16, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZNSt3__18time_putIcNS_19ostreambuf_iteratorIcNS_11char_traitsIcEEEEE2idE', 'size': 16, 'type': 'OBJECT'}
 {'is_defined': True, 'name': '_ZNSt3__18time_putIwNS_19ostreambuf_iteratorIwNS_11char_traitsIwEEEEE2idE', 'size': 16, 'type': 'OBJECT'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_d', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_dNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_dNS_12chars_formatEi', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_e', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_eNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_eNS_12chars_formatEi', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_f', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_fNS_12chars_formatE', 'type': 'FUNC'}
+{'is_defined': True, 'name': '_ZNSt3__18to_charsEPcS0_fNS_12chars_formatEi', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__18valarrayImE6resizeEmm', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__18valarrayImEC1Em', 'type': 'FUNC'}
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 {'is_defined': True, 'name': '_ZNSt3__19__num_getIcE17__stage2_int_loopEciPcRS2_RjcRKNS_12basic_stringIcNS_11char_traitsIcEENS_9allocatorIcEEEEPjRSD_S2_', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZNSt3__19__num_getIcE17__stage2_int_prepERNS_8ios_baseEPcRc', 'type': 'FUNC'}
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 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__113basic_ostreamIcNS_11char_traitsIcEEED0Ev', 'type': 'FUNC'}
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 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__114basic_iostreamIcNS_11char_traitsIcEEED0Ev', 'type': 'FUNC'}
 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__114basic_iostreamIcNS_11char_traitsIcEEED1Ev', 'type': 'FUNC'}
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 {'is_defined': True, 'name': '_ZTv0_n24_NSt3__19strstreamD1Ev', 'type': 'FUNC'}
 No newline at end of file

libcxx/src/CMakeLists.txt

 set(LIBCXX_LIB_CMAKEFILES_DIR "${CMAKE_CURRENT_BINARY_DIR}${CMAKE_FILES_DIRECTORY}"  PARENT_SCOPE)
 
 # Get sources
 set(LIBCXX_SOURCES
   algorithm.cpp
   any.cpp
   atomic.cpp
   barrier.cpp
   bind.cpp
   charconv.cpp
   chrono.cpp
   condition_variable.cpp
   condition_variable_destructor.cpp
   exception.cpp
   functional.cpp
   future.cpp
   hash.cpp
   include/apple_availability.h
   include/atomic_support.h
   include/config_elast.h
   include/refstring.h
+  include/ryu/common.h
+  include/ryu/d2fixed.h
+  include/ryu/d2fixed_full_table.h
+  include/ryu/d2s.h
+  include/ryu/d2s_full_table.h
+  include/ryu/d2s_intrinsics.h
+  include/ryu/digit_table.h
+  include/ryu/f2s.h
+  include/ryu/ryu.h
+  include/to_chars_floating_point.h
   legacy_pointer_safety.cpp
   memory.cpp
   mutex.cpp
   mutex_destructor.cpp
   new.cpp
   optional.cpp
   random_shuffle.cpp
+  ryu/d2fixed.cpp
+  ryu/d2s.cpp
+  ryu/f2s.cpp
   shared_mutex.cpp
   stdexcept.cpp
   string.cpp
   support/runtime/exception_fallback.ipp
   support/runtime/exception_glibcxx.ipp
   support/runtime/exception_libcxxabi.ipp
   support/runtime/exception_libcxxrt.ipp
   support/runtime/exception_msvc.ipp

libcxx/src/charconv.cpp

 //===----------------------------------------------------------------------===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include "charconv"
 #include <string.h>
 
+#include "include/ryu/digit_table.h"
+#include "include/to_chars_floating_point.h"
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 namespace __itoa
 {
 
-static constexpr char cDigitsLut[200] = {
-    '0', '0', '0', '1', '0', '2', '0', '3', '0', '4', '0', '5', '0', '6', '0',
-    '7', '0', '8', '0', '9', '1', '0', '1', '1', '1', '2', '1', '3', '1', '4',
-    '1', '5', '1', '6', '1', '7', '1', '8', '1', '9', '2', '0', '2', '1', '2',
-    '2', '2', '3', '2', '4', '2', '5', '2', '6', '2', '7', '2', '8', '2', '9',
-    '3', '0', '3', '1', '3', '2', '3', '3', '3', '4', '3', '5', '3', '6', '3',
-    '7', '3', '8', '3', '9', '4', '0', '4', '1', '4', '2', '4', '3', '4', '4',
-    '4', '5', '4', '6', '4', '7', '4', '8', '4', '9', '5', '0', '5', '1', '5',
-    '2', '5', '3', '5', '4', '5', '5', '5', '6', '5', '7', '5', '8', '5', '9',
-    '6', '0', '6', '1', '6', '2', '6', '3', '6', '4', '6', '5', '6', '6', '6',
-    '7', '6', '8', '6', '9', '7', '0', '7', '1', '7', '2', '7', '3', '7', '4',
-    '7', '5', '7', '6', '7', '7', '7', '8', '7', '9', '8', '0', '8', '1', '8',
-    '2', '8', '3', '8', '4', '8', '5', '8', '6', '8', '7', '8', '8', '8', '9',
-    '9', '0', '9', '1', '9', '2', '9', '3', '9', '4', '9', '5', '9', '6', '9',
-    '7', '9', '8', '9', '9'};
-
 template <typename T>
 inline _LIBCPP_INLINE_VISIBILITY char*
 append1(char* buffer, T i) noexcept
 {
     *buffer = '0' + static_cast<char>(i);
     return buffer + 1;
 }
 
 template <typename T>
 inline _LIBCPP_INLINE_VISIBILITY char*
 append2(char* buffer, T i) noexcept
 {
-    memcpy(buffer, &cDigitsLut[(i)*2], 2);
+    memcpy(buffer, &__DIGIT_TABLE[(i)*2], 2);
     return buffer + 2;
 }
 
 template <typename T>
 inline _LIBCPP_INLINE_VISIBILITY char*
 append3(char* buffer, T i) noexcept
 {
     return append2(append1(buffer, (i) / 100), (i) % 100);
else
         buffer = append4(buffer, v1 % 10000);
     }
 
     return buffer;
 }
 
 }  // namespace __itoa
 
+// The original version of floating-point to_chars was written by Microsoft and
+// contributed with the following license.
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// This implementation is dedicated to the memory of Mary and Thavatchai.
+
+to_chars_result to_chars(char* __first, char* __last, float __value) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Plain>(__first, __last, __value, chars_format{}, 0);
+}
+
+to_chars_result to_chars(char* __first, char* __last, double __value) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Plain>(__first, __last, __value, chars_format{}, 0);
+}
+
+to_chars_result to_chars(char* __first, char* __last, long double __value) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Plain>(__first, __last, static_cast<double>(__value),
+                                                                 chars_format{}, 0);
+}
+
+to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Format_only>(__first, __last, __value, __fmt, 0);
+}
+
+to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Format_only>(__first, __last, __value, __fmt, 0);
+}
+
+to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Format_only>(__first, __last, static_cast<double>(__value),
+                                                                       __fmt, 0);
+}
+
+to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Format_precision>(__first, __last, __value, __fmt,
+                                                                            __precision);
+}
+
+to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Format_precision>(__first, __last, __value, __fmt,
+                                                                            __precision);
+}
+
+to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision) {
+  return _Floating_to_chars<_Floating_to_chars_overload::_Format_precision>(
+      __first, __last, static_cast<double>(__value), __fmt, __precision);
+}
+
 _LIBCPP_END_NAMESPACE_STD

libcxx/src/include/ryu/common.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_COMMON_H
+#define _LIBCPP_SRC_INCLUDE_RYU_COMMON_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __decimalLength9(const uint32_t __v) {
+  // Function precondition: __v is not a 10-digit number.
+  // (f2s: 9 digits are sufficient for round-tripping.)
+  // (d2fixed: We print 9-digit blocks.)
+  _LIBCPP_ASSERT(__v < 1000000000, "");
+  if (__v >= 100000000) { return 9; }
+  if (__v >= 10000000) { return 8; }
+  if (__v >= 1000000) { return 7; }
+  if (__v >= 100000) { return 6; }
+  if (__v >= 10000) { return 5; }
+  if (__v >= 1000) { return 4; }
+  if (__v >= 100) { return 3; }
+  if (__v >= 10) { return 2; }
+  return 1;
+}
+
+// Returns __e == 0 ? 1 : ceil(log_2(5^__e)).
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI  inline int32_t __pow5bits(const int32_t __e) {
+  // This approximation works up to the point that the multiplication overflows at __e = 3529.
+  // If the multiplication were done in 64 bits, it would fail at 5^4004 which is just greater
+  // than 2^9297.
+  _LIBCPP_ASSERT(__e >= 0, "");
+  _LIBCPP_ASSERT(__e <= 3528, "");
+  return static_cast<int32_t>(((static_cast<uint32_t>(__e) * 1217359) >> 19) + 1);
+}
+
+// Returns floor(log_10(2^__e)).
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI  inline uint32_t __log10Pow2(const int32_t __e) {
+  // The first value this approximation fails for is 2^1651 which is just greater than 10^297.
+  _LIBCPP_ASSERT(__e >= 0, "");
+  _LIBCPP_ASSERT(__e <= 1650, "");
+  return (static_cast<uint32_t>(__e) * 78913) >> 18;
+}
+
+// Returns floor(log_10(5^__e)).
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __log10Pow5(const int32_t __e) {
+  // The first value this approximation fails for is 5^2621 which is just greater than 10^1832.
+  _LIBCPP_ASSERT(__e >= 0, "");
+  _LIBCPP_ASSERT(__e <= 2620, "");
+  return (static_cast<uint32_t>(__e) * 732923) >> 20;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __float_to_bits(const float __f) {
+  uint32_t __bits = 0;
+  _VSTD::memcpy(&__bits, &__f, sizeof(float));
+  return __bits;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __double_to_bits(const double __d) {
+  uint64_t __bits = 0;
+  _VSTD::memcpy(&__bits, &__d, sizeof(double));
+  return __bits;
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_COMMON_H

libcxx/src/include/ryu/d2fixed.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_D2FIXED_H
+#define _LIBCPP_SRC_INCLUDE_RYU_D2FIXED_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+#include "cstdint"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+void __append_n_digits(const uint32_t __olength, uint32_t __digits, char* const __result);
+void __append_nine_digits(uint32_t __digits, char* const __result);
+
+[[nodiscard]] to_chars_result __d2fixed_buffered_n(char* _First, char* const _Last, const double __d, const uint32_t __precision);
+[[nodiscard]] to_chars_result __d2exp_buffered_n(char* _First, char* const _Last, const double __d, uint32_t __precision);
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_D2FIXED_H

libcxx/src/include/ryu/d2s.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_DS2_H
+#define _LIBCPP_SRC_INCLUDE_RYU_DS2_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline constexpr int __DOUBLE_MANTISSA_BITS = 52;
+inline constexpr int __DOUBLE_EXPONENT_BITS = 11;
+inline constexpr int __DOUBLE_BIAS = 1023;
+
+inline constexpr int __DOUBLE_POW5_INV_BITCOUNT = 122;
+inline constexpr int __DOUBLE_POW5_BITCOUNT = 121;
+
+[[nodiscard]] to_chars_result __d2s_buffered_n(char* const _First, char* const _Last, const double __f, const chars_format _Fmt);
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_DS2_H

libcxx/src/include/ryu/d2s_full_table.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_D2S_FULL_TABLE_H
+#define _LIBCPP_SRC_INCLUDE_RYU_D2S_FULL_TABLE_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline constexpr uint64_t __DOUBLE_POW5_INV_SPLIT[292][2] = {
+  {                    1u, 288230376151711744u }, {  3689348814741910324u, 230584300921369395u },
+  {  2951479051793528259u, 184467440737095516u }, { 17118578500402463900u, 147573952589676412u },
+  { 12632330341676300947u, 236118324143482260u }, { 10105864273341040758u, 188894659314785808u },
+  { 15463389048156653253u, 151115727451828646u }, { 17362724847566824558u, 241785163922925834u },
+  { 17579528692795369969u, 193428131138340667u }, {  6684925324752475329u, 154742504910672534u },
+  { 18074578149087781173u, 247588007857076054u }, { 18149011334012135262u, 198070406285660843u },
+  {  3451162622983977240u, 158456325028528675u }, {  5521860196774363583u, 253530120045645880u },
+  {  4417488157419490867u, 202824096036516704u }, {  7223339340677503017u, 162259276829213363u },
+  {  7867994130342094503u, 259614842926741381u }, {  2605046489531765280u, 207691874341393105u },
+  {  2084037191625412224u, 166153499473114484u }, { 10713157136084480204u, 265845599156983174u },
+  { 12259874523609494487u, 212676479325586539u }, { 13497248433629505913u, 170141183460469231u },
+  { 14216899864323388813u, 272225893536750770u }, { 11373519891458711051u, 217780714829400616u },
+  {  5409467098425058518u, 174224571863520493u }, {  4965798542738183305u, 278759314981632789u },
+  {  7661987648932456967u, 223007451985306231u }, {  2440241304404055250u, 178405961588244985u },
+  {  3904386087046488400u, 285449538541191976u }, { 17880904128604832013u, 228359630832953580u },
+  { 14304723302883865611u, 182687704666362864u }, { 15133127457049002812u, 146150163733090291u },
+  { 16834306301794583852u, 233840261972944466u }, {  9778096226693756759u, 187072209578355573u },
+  { 15201174610838826053u, 149657767662684458u }, {  2185786488890659746u, 239452428260295134u },
+  {  5437978005854438120u, 191561942608236107u }, { 15418428848909281466u, 153249554086588885u },
+  {  6222742084545298729u, 245199286538542217u }, { 16046240111861969953u, 196159429230833773u },
+  {  1768945645263844993u, 156927543384667019u }, { 10209010661905972635u, 251084069415467230u },
+  {  8167208529524778108u, 200867255532373784u }, { 10223115638361732810u, 160693804425899027u },
+  {  1599589762411131202u, 257110087081438444u }, {  4969020624670815285u, 205688069665150755u },
+  {  3975216499736652228u, 164550455732120604u }, { 13739044029062464211u, 263280729171392966u },
+  {  7301886408508061046u, 210624583337114373u }, { 13220206756290269483u, 168499666669691498u },
+  { 17462981995322520850u, 269599466671506397u }, {  6591687966774196033u, 215679573337205118u },
+  { 12652048002903177473u, 172543658669764094u }, {  9175230360419352987u, 276069853871622551u },
+  {  3650835473593572067u, 220855883097298041u }, { 17678063637842498946u, 176684706477838432u },
+  { 13527506561580357021u, 282695530364541492u }, {  3443307619780464970u, 226156424291633194u },
+  {  6443994910566282300u, 180925139433306555u }, {  5155195928453025840u, 144740111546645244u },
+  { 15627011115008661990u, 231584178474632390u }, { 12501608892006929592u, 185267342779705912u },
+  {  2622589484121723027u, 148213874223764730u }, {  4196143174594756843u, 237142198758023568u },
+  { 10735612169159626121u, 189713759006418854u }, { 12277838550069611220u, 151771007205135083u },
+  { 15955192865369467629u, 242833611528216133u }, {  1696107848069843133u, 194266889222572907u },
+  { 12424932722681605476u, 155413511378058325u }, {  1433148282581017146u, 248661618204893321u },
+  { 15903913885032455010u, 198929294563914656u }, {  9033782293284053685u, 159143435651131725u },
+  { 14454051669254485895u, 254629497041810760u }, { 11563241335403588716u, 203703597633448608u },
+  { 16629290697806691620u, 162962878106758886u }, {   781423413297334329u, 260740604970814219u },
+  {  4314487545379777786u, 208592483976651375u }, {  3451590036303822229u, 166873987181321100u },
+  {  5522544058086115566u, 266998379490113760u }, {  4418035246468892453u, 213598703592091008u },
+  { 10913125826658934609u, 170878962873672806u }, { 10082303693170474728u, 273406340597876490u },
+  {  8065842954536379782u, 218725072478301192u }, { 17520720807854834795u, 174980057982640953u },
+  {  5897060404116273733u, 279968092772225526u }, {  1028299508551108663u, 223974474217780421u },
+  { 15580034865808528224u, 179179579374224336u }, { 17549358155809824511u, 286687326998758938u },
+  {  2971440080422128639u, 229349861599007151u }, { 17134547323305344204u, 183479889279205720u },
+  { 13707637858644275364u, 146783911423364576u }, { 14553522944347019935u, 234854258277383322u },
+  {  4264120725993795302u, 187883406621906658u }, { 10789994210278856888u, 150306725297525326u },
+  {  9885293106962350374u, 240490760476040522u }, {   529536856086059653u, 192392608380832418u },
+  {  7802327114352668369u, 153914086704665934u }, {  1415676938738538420u, 246262538727465495u },
+  {  1132541550990830736u, 197010030981972396u }, { 15663428499760305882u, 157608024785577916u },
+  { 17682787970132668764u, 252172839656924666u }, { 10456881561364224688u, 201738271725539733u },
+  { 15744202878575200397u, 161390617380431786u }, { 17812026976236499989u, 258224987808690858u },
+  {  3181575136763469022u, 206579990246952687u }, { 13613306553636506187u, 165263992197562149u },
+  { 10713244041592678929u, 264422387516099439u }, { 12259944048016053467u, 211537910012879551u },
+  {  6118606423670932450u, 169230328010303641u }, {  2411072648389671274u, 270768524816485826u },
+  { 16686253377679378312u, 216614819853188660u }, { 13349002702143502650u, 173291855882550928u },
+  { 17669055508687693916u, 277266969412081485u }, { 14135244406950155133u, 221813575529665188u },
+  {   240149081334393137u, 177450860423732151u }, { 11452284974360759988u, 283921376677971441u },
+  {  5472479164746697667u, 227137101342377153u }, { 11756680961281178780u, 181709681073901722u },
+  {  2026647139541122378u, 145367744859121378u }, { 18000030682233437097u, 232588391774594204u },
+  { 18089373360528660001u, 186070713419675363u }, {  3403452244197197031u, 148856570735740291u },
+  { 16513570034941246220u, 238170513177184465u }, { 13210856027952996976u, 190536410541747572u },
+  {  3189987192878576934u, 152429128433398058u }, {  1414630693863812771u, 243886605493436893u },
+  {  8510402184574870864u, 195109284394749514u }, { 10497670562401807014u, 156087427515799611u },
+  {  9417575270359070576u, 249739884025279378u }, { 14912757845771077107u, 199791907220223502u },
+  {  4551508647133041040u, 159833525776178802u }, { 10971762650154775986u, 255733641241886083u },
+  { 16156107749607641435u, 204586912993508866u }, {  9235537384944202825u, 163669530394807093u },
+  { 11087511001168814197u, 261871248631691349u }, { 12559357615676961681u, 209496998905353079u },
+  { 13736834907283479668u, 167597599124282463u }, { 18289587036911657145u, 268156158598851941u },
+  { 10942320814787415393u, 214524926879081553u }, { 16132554281313752961u, 171619941503265242u },
+  { 11054691591134363444u, 274591906405224388u }, { 16222450902391311402u, 219673525124179510u },
+  { 12977960721913049122u, 175738820099343608u }, { 17075388340318968271u, 281182112158949773u },
+  {  2592264228029443648u, 224945689727159819u }, {  5763160197165465241u, 179956551781727855u },
+  {  9221056315464744386u, 287930482850764568u }, { 14755542681855616155u, 230344386280611654u },
+  { 15493782960226403247u, 184275509024489323u }, {  1326979923955391628u, 147420407219591459u },
+  {  9501865507812447252u, 235872651551346334u }, { 11290841220991868125u, 188698121241077067u },
+  {  1653975347309673853u, 150958496992861654u }, { 10025058185179298811u, 241533595188578646u },
+  {  4330697733401528726u, 193226876150862917u }, { 14532604630946953951u, 154581500920690333u },
+  {  1116074521063664381u, 247330401473104534u }, {  4582208431592841828u, 197864321178483627u },
+  { 14733813189500004432u, 158291456942786901u }, { 16195403473716186445u, 253266331108459042u },
+  {  5577625149489128510u, 202613064886767234u }, {  8151448934333213131u, 162090451909413787u },
+  { 16731667109675051333u, 259344723055062059u }, { 17074682502481951390u, 207475778444049647u },
+  {  6281048372501740465u, 165980622755239718u }, {  6360328581260874421u, 265568996408383549u },
+  {  8777611679750609860u, 212455197126706839u }, { 10711438158542398211u, 169964157701365471u },
+  {  9759603424184016492u, 271942652322184754u }, { 11497031554089123517u, 217554121857747803u },
+  { 16576322872755119460u, 174043297486198242u }, { 11764721337440549842u, 278469275977917188u },
+  { 16790474699436260520u, 222775420782333750u }, { 13432379759549008416u, 178220336625867000u },
+  {  3045063541568861850u, 285152538601387201u }, { 17193446092222730773u, 228122030881109760u },
+  { 13754756873778184618u, 182497624704887808u }, { 18382503128506368341u, 145998099763910246u },
+  {  3586563302416817083u, 233596959622256395u }, {  2869250641933453667u, 186877567697805116u },
+  { 17052795772514404226u, 149502054158244092u }, { 12527077977055405469u, 239203286653190548u },
+  { 17400360011128145022u, 191362629322552438u }, {  2852241564676785048u, 153090103458041951u },
+  { 15631632947708587046u, 244944165532867121u }, {  8815957543424959314u, 195955332426293697u },
+  { 18120812478965698421u, 156764265941034957u }, { 14235904707377476180u, 250822825505655932u },
+  {  4010026136418160298u, 200658260404524746u }, { 17965416168102169531u, 160526608323619796u },
+  {  2919224165770098987u, 256842573317791675u }, {  2335379332616079190u, 205474058654233340u },
+  {  1868303466092863352u, 164379246923386672u }, {  6678634360490491686u, 263006795077418675u },
+  {  5342907488392393349u, 210405436061934940u }, {  4274325990713914679u, 168324348849547952u },
+  { 10528270399884173809u, 269318958159276723u }, { 15801313949391159694u, 215455166527421378u },
+  {  1573004715287196786u, 172364133221937103u }, { 17274202803427156150u, 275782613155099364u },
+  { 17508711057483635243u, 220626090524079491u }, { 10317620031244997871u, 176500872419263593u },
+  { 12818843235250086271u, 282401395870821749u }, { 13944423402941979340u, 225921116696657399u },
+  { 14844887537095493795u, 180736893357325919u }, { 15565258844418305359u, 144589514685860735u },
+  {  6457670077359736959u, 231343223497377177u }, { 16234182506113520537u, 185074578797901741u },
+  {  9297997190148906106u, 148059663038321393u }, { 11187446689496339446u, 236895460861314229u },
+  { 12639306166338981880u, 189516368689051383u }, { 17490142562555006151u, 151613094951241106u },
+  {  2158786396894637579u, 242580951921985771u }, { 16484424376483351356u, 194064761537588616u },
+  {  9498190686444770762u, 155251809230070893u }, { 11507756283569722895u, 248402894768113429u },
+  { 12895553841597688639u, 198722315814490743u }, { 17695140702761971558u, 158977852651592594u },
+  { 17244178680193423523u, 254364564242548151u }, { 10105994129412828495u, 203491651394038521u },
+  {  4395446488788352473u, 162793321115230817u }, { 10722063196803274280u, 260469313784369307u },
+  {  1198952927958798777u, 208375451027495446u }, { 15716557601334680315u, 166700360821996356u },
+  { 17767794532651667857u, 266720577315194170u }, { 14214235626121334286u, 213376461852155336u },
+  {  7682039686155157106u, 170701169481724269u }, {  1223217053622520399u, 273121871170758831u },
+  { 15735968901865657612u, 218497496936607064u }, { 16278123936234436413u, 174797997549285651u },
+  {   219556594781725998u, 279676796078857043u }, {  7554342905309201445u, 223741436863085634u },
+  {  9732823138989271479u, 178993149490468507u }, {   815121763415193074u, 286389039184749612u },
+  { 11720143854957885429u, 229111231347799689u }, { 13065463898708218666u, 183288985078239751u },
+  {  6763022304224664610u, 146631188062591801u }, {  3442138057275642729u, 234609900900146882u },
+  { 13821756890046245153u, 187687920720117505u }, { 11057405512036996122u, 150150336576094004u },
+  {  6623802375033462826u, 240240538521750407u }, { 16367088344252501231u, 192192430817400325u },
+  { 13093670675402000985u, 153753944653920260u }, {  2503129006933649959u, 246006311446272417u },
+  { 13070549649772650937u, 196805049157017933u }, { 17835137349301941396u, 157444039325614346u },
+  {  2710778055689733971u, 251910462920982955u }, {  2168622444551787177u, 201528370336786364u },
+  {  5424246770383340065u, 161222696269429091u }, {  1300097203129523457u, 257956314031086546u },
+  { 15797473021471260058u, 206365051224869236u }, {  8948629602435097724u, 165092040979895389u },
+  {  3249760919670425388u, 264147265567832623u }, {  9978506365220160957u, 211317812454266098u },
+  { 15361502721659949412u, 169054249963412878u }, {  2442311466204457120u, 270486799941460606u },
+  { 16711244431931206989u, 216389439953168484u }, { 17058344360286875914u, 173111551962534787u },
+  { 12535955717491360170u, 276978483140055660u }, { 10028764573993088136u, 221582786512044528u },
+  { 15401709288678291155u, 177266229209635622u }, {  9885339602917624555u, 283625966735416996u },
+  {  4218922867592189321u, 226900773388333597u }, { 14443184738299482427u, 181520618710666877u },
+  {  4175850161155765295u, 145216494968533502u }, { 10370709072591134795u, 232346391949653603u },
+  { 15675264887556728482u, 185877113559722882u }, {  5161514280561562140u, 148701690847778306u },
+  {   879725219414678777u, 237922705356445290u }, {   703780175531743021u, 190338164285156232u },
+  { 11631070584651125387u, 152270531428124985u }, {   162968861732249003u, 243632850284999977u },
+  { 11198421533611530172u, 194906280227999981u }, {  5269388412147313814u, 155925024182399985u },
+  {  8431021459435702103u, 249480038691839976u }, {  3055468352806651359u, 199584030953471981u },
+  { 17201769941212962380u, 159667224762777584u }, { 16454785461715008838u, 255467559620444135u },
+  { 13163828369372007071u, 204374047696355308u }, { 17909760324981426303u, 163499238157084246u },
+  {  2830174816776909822u, 261598781051334795u }, {  2264139853421527858u, 209279024841067836u },
+  { 16568707141704863579u, 167423219872854268u }, {  4373838538276319787u, 267877151796566830u },
+  {  3499070830621055830u, 214301721437253464u }, {  6488605479238754987u, 171441377149802771u },
+  {  3003071137298187333u, 274306203439684434u }, {  6091805724580460189u, 219444962751747547u },
+  { 15941491023890099121u, 175555970201398037u }, { 10748990379256517301u, 280889552322236860u },
+  {  8599192303405213841u, 224711641857789488u }, { 14258051472207991719u, 179769313486231590u }
+};
+
+inline constexpr uint64_t __DOUBLE_POW5_SPLIT[326][2] = {
+  {                    0u,  72057594037927936u }, {                    0u,  90071992547409920u },
+  {                    0u, 112589990684262400u }, {                    0u, 140737488355328000u },
+  {                    0u,  87960930222080000u }, {                    0u, 109951162777600000u },
+  {                    0u, 137438953472000000u }, {                    0u,  85899345920000000u },
+  {                    0u, 107374182400000000u }, {                    0u, 134217728000000000u },
+  {                    0u,  83886080000000000u }, {                    0u, 104857600000000000u },
+  {                    0u, 131072000000000000u }, {                    0u,  81920000000000000u },
+  {                    0u, 102400000000000000u }, {                    0u, 128000000000000000u },
+  {                    0u,  80000000000000000u }, {                    0u, 100000000000000000u },
+  {                    0u, 125000000000000000u }, {                    0u,  78125000000000000u },
+  {                    0u,  97656250000000000u }, {                    0u, 122070312500000000u },
+  {                    0u,  76293945312500000u }, {                    0u,  95367431640625000u },
+  {                    0u, 119209289550781250u }, {  4611686018427387904u,  74505805969238281u },
+  { 10376293541461622784u,  93132257461547851u }, {  8358680908399640576u, 116415321826934814u },
+  {   612489549322387456u,  72759576141834259u }, { 14600669991935148032u,  90949470177292823u },
+  { 13639151471491547136u, 113686837721616029u }, {  3213881284082270208u, 142108547152020037u },
+  {  4314518811765112832u,  88817841970012523u }, {   781462496279003136u, 111022302462515654u },
+  { 10200200157203529728u, 138777878078144567u }, { 13292654125893287936u,  86736173798840354u },
+  {  7392445620511834112u, 108420217248550443u }, {  4628871007212404736u, 135525271560688054u },
+  { 16728102434789916672u,  84703294725430033u }, {  7075069988205232128u, 105879118406787542u },
+  { 18067209522111315968u, 132348898008484427u }, {  8986162942105878528u,  82718061255302767u },
+  {  6621017659204960256u, 103397576569128459u }, {  3664586055578812416u, 129246970711410574u },
+  { 16125424340018921472u,  80779356694631608u }, {  1710036351314100224u, 100974195868289511u },
+  { 15972603494424788992u, 126217744835361888u }, {  9982877184015493120u,  78886090522101180u },
+  { 12478596480019366400u,  98607613152626475u }, { 10986559581596820096u, 123259516440783094u },
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+  { 17216279797195927585u, 124052012916201195u }, {  8454331864033760789u,  77532508072625747u },
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+  {  9264989777501460624u,  75715339914673581u }, { 16192923240304213684u,  94644174893341976u },
+  {  1794409976670715490u, 118305218616677471u }, {  8039035263060279037u,  73940761635423419u },
+  {  5437108060397960892u,  92425952044279274u }, { 16019757112352226923u, 115532440055349092u },
+  {   788976158365366019u,  72207775034593183u }, { 14821278253238871236u,  90259718793241478u },
+  {  9303225779693813237u, 112824648491551848u }, { 11629032224617266546u, 141030810614439810u },
+  { 11879831158813179495u,  88144256634024881u }, {  1014730893234310657u, 110180320792531102u },
+  { 10491785653397664129u, 137725400990663877u }, {  8863209042587234033u,  86078375619164923u },
+  {  6467325284806654637u, 107597969523956154u }, { 17307528642863094104u, 134497461904945192u },
+  { 10817205401789433815u,  84060913690590745u }, { 18133192770664180173u, 105076142113238431u },
+  { 18054804944902837312u, 131345177641548039u }, { 18201782118205355176u,  82090736025967524u },
+  {  4305483574047142354u, 102613420032459406u }, { 14605226504413703751u, 128266775040574257u },
+  {  2210737537617482988u,  80166734400358911u }, { 16598479977304017447u, 100208418000448638u },
+  { 11524727934775246001u, 125260522500560798u }, {  2591268940807140847u,  78287826562850499u },
+  { 17074144231291089770u,  97859783203563123u }, { 16730994270686474309u, 122324729004453904u },
+  { 10456871419179046443u,  76452955627783690u }, {  3847717237119032246u,  95566194534729613u },
+  {  9421332564826178211u, 119457743168412016u }, {  5888332853016361382u,  74661089480257510u },
+  { 16583788103125227536u,  93326361850321887u }, { 16118049110479146516u, 116657952312902359u },
+  { 16991309721690548428u,  72911220195563974u }, { 12015765115258409727u,  91139025244454968u },
+  { 15019706394073012159u, 113923781555568710u }, {  9551260955736489391u, 142404726944460888u },
+  {  5969538097335305869u,  89002954340288055u }, {  2850236603241744433u, 111253692925360069u }
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_D2S_FULL_TABLE_H

libcxx/src/include/ryu/d2s_intrinsics.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_DS2_INTRINSICS_H
+#define _LIBCPP_SRC_INCLUDE_RYU_DS2_INTRINSICS_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if defined(_M_X64) && defined(_MSC_VER)
+#define _LIBCPP_INTRINSIC128 1
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __ryu_umul128(const uint64_t __a, const uint64_t __b, uint64_t* const __productHi) {
+  return _umul128(__a, __b, __productHi);
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __ryu_shiftright128(const uint64_t __lo, const uint64_t __hi, const uint32_t __dist) {
+  // For the __shiftright128 intrinsic, the shift value is always
+  // modulo 64.
+  // In the current implementation of the double-precision version
+  // of Ryu, the shift value is always < 64.
+  // (The shift value is in the range [49, 58].)
+  // Check this here in case a future change requires larger shift
+  // values. In this case this function needs to be adjusted.
+  _LIBCPP_ASSERT(__dist < 64, "");
+  return __shiftright128(__lo, __hi, static_cast<unsigned char>(__dist));
+}
+
+// ^^^ intrinsics available ^^^ / vvv __int128 available vvv
+#elif defined(__SIZEOF_INT128__) && ( \
+    (defined(__clang__) && !defined(_MSC_VER)) || \
+    (defined(__GNUC__) && !defined(__clang__) && !defined(__CUDACC__)))
+#define _LIBCPP_INTRINSIC128 1
+  // We have __uint128 support in clang or gcc
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __ryu_umul128(const uint64_t __a, const uint64_t __b, uint64_t* const __productHi) {
+  auto __temp = __a * (unsigned __int128)__b;
+  *__productHi = __temp >> 64;
+  return static_cast<uint64_t>(__temp);
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __ryu_shiftright128(const uint64_t __lo, const uint64_t __hi, const uint32_t __dist) {
+  // In the current implementation of the double-precision version
+  // of Ryu, the shift value is always < 64.
+  // (The shift value is in the range [49, 58].)
+  // Check this here in case a future change requires larger shift
+  // values. In this case this function needs to be adjusted.
+  _LIBCPP_ASSERT(__dist < 64, "");
+  auto __temp = __lo | ((unsigned __int128)__hi << 64);
+  // For x64 128-bit shfits using the `shrd` instruction and two 64-bit
+  // registers, the shift value is modulo 64.  Thus the `& 63` is free.
+  return static_cast<uint64_t>(__temp >> (__dist & 63));
+}
+#else // ^^^ __int128 available ^^^ / vvv intrinsics unavailable vvv
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline _LIBCPP_ALWAYS_INLINE uint64_t __ryu_umul128(const uint64_t __a, const uint64_t __b, uint64_t* const __productHi) {
+  // TRANSITION, VSO-634761
+  // The casts here help MSVC to avoid calls to the __allmul library function.
+  const uint32_t __aLo = static_cast<uint32_t>(__a);
+  const uint32_t __aHi = static_cast<uint32_t>(__a >> 32);
+  const uint32_t __bLo = static_cast<uint32_t>(__b);
+  const uint32_t __bHi = static_cast<uint32_t>(__b >> 32);
+
+  const uint64_t __b00 = static_cast<uint64_t>(__aLo) * __bLo;
+  const uint64_t __b01 = static_cast<uint64_t>(__aLo) * __bHi;
+  const uint64_t __b10 = static_cast<uint64_t>(__aHi) * __bLo;
+  const uint64_t __b11 = static_cast<uint64_t>(__aHi) * __bHi;
+
+  const uint32_t __b00Lo = static_cast<uint32_t>(__b00);
+  const uint32_t __b00Hi = static_cast<uint32_t>(__b00 >> 32);
+
+  const uint64_t __mid1 = __b10 + __b00Hi;
+  const uint32_t __mid1Lo = static_cast<uint32_t>(__mid1);
+  const uint32_t __mid1Hi = static_cast<uint32_t>(__mid1 >> 32);
+
+  const uint64_t __mid2 = __b01 + __mid1Lo;
+  const uint32_t __mid2Lo = static_cast<uint32_t>(__mid2);
+  const uint32_t __mid2Hi = static_cast<uint32_t>(__mid2 >> 32);
+
+  const uint64_t __pHi = __b11 + __mid1Hi + __mid2Hi;
+  const uint64_t __pLo = (static_cast<uint64_t>(__mid2Lo) << 32) | __b00Lo;
+
+  *__productHi = __pHi;
+  return __pLo;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __ryu_shiftright128(const uint64_t __lo, const uint64_t __hi, const uint32_t __dist) {
+  // We don't need to handle the case __dist >= 64 here (see above).
+  _LIBCPP_ASSERT(__dist < 64, "");
+#ifdef _LIBCPP_64_BIT
+  _LIBCPP_ASSERT(__dist > 0, "");
+  return (__hi << (64 - __dist)) | (__lo >> __dist);
+#else // ^^^ 64-bit ^^^ / vvv 32-bit vvv
+  // Avoid a 64-bit shift by taking advantage of the range of shift values.
+  _LIBCPP_ASSERT(__dist >= 32, "");
+  return (__hi << (64 - __dist)) | (static_cast<uint32_t>(__lo >> 32) >> (__dist - 32));
+#endif // ^^^ 32-bit ^^^
+}
+
+#endif // ^^^ intrinsics unavailable ^^^
+
+#ifndef _LIBCPP_64_BIT
+
+// Returns the high 64 bits of the 128-bit product of __a and __b.
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __umulh(const uint64_t __a, const uint64_t __b) {
+  // Reuse the __ryu_umul128 implementation.
+  // Optimizers will likely eliminate the instructions used to compute the
+  // low part of the product.
+  uint64_t __hi;
+  (void) __ryu_umul128(__a, __b, &__hi);
+  return __hi;
+}
+
+// On 32-bit platforms, compilers typically generate calls to library
+// functions for 64-bit divisions, even if the divisor is a constant.
+//
+// TRANSITION, LLVM-37932
+//
+// The functions here perform division-by-constant using multiplications
+// in the same way as 64-bit compilers would do.
+//
+// NB:
+// The multipliers and shift values are the ones generated by clang x64
+// for expressions like x/5, x/10, etc.
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div5(const uint64_t __x) {
+  return __umulh(__x, 0xCCCCCCCCCCCCCCCDu) >> 2;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div10(const uint64_t __x) {
+  return __umulh(__x, 0xCCCCCCCCCCCCCCCDu) >> 3;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div100(const uint64_t __x) {
+  return __umulh(__x >> 2, 0x28F5C28F5C28F5C3u) >> 2;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div1e8(const uint64_t __x) {
+  return __umulh(__x, 0xABCC77118461CEFDu) >> 26;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div1e9(const uint64_t __x) {
+  return __umulh(__x >> 9, 0x44B82FA09B5A53u) >> 11;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mod1e9(const uint64_t __x) {
+  // Avoid 64-bit math as much as possible.
+  // Returning static_cast<uint32_t>(__x - 1000000000 * __div1e9(__x)) would
+  // perform 32x64-bit multiplication and 64-bit subtraction.
+  // __x and 1000000000 * __div1e9(__x) are guaranteed to differ by
+  // less than 10^9, so their highest 32 bits must be identical,
+  // so we can truncate both sides to uint32_t before subtracting.
+  // We can also simplify static_cast<uint32_t>(1000000000 * __div1e9(__x)).
+  // We can truncate before multiplying instead of after, as multiplying
+  // the highest 32 bits of __div1e9(__x) can't affect the lowest 32 bits.
+  return static_cast<uint32_t>(__x) - 1000000000 * static_cast<uint32_t>(__div1e9(__x));
+}
+
+#else // ^^^ 32-bit ^^^ / vvv 64-bit vvv
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div5(const uint64_t __x) {
+  return __x / 5;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div10(const uint64_t __x) {
+  return __x / 10;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div100(const uint64_t __x) {
+  return __x / 100;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div1e8(const uint64_t __x) {
+  return __x / 100000000;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __div1e9(const uint64_t __x) {
+  return __x / 1000000000;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mod1e9(const uint64_t __x) {
+  return static_cast<uint32_t>(__x - 1000000000 * __div1e9(__x));
+}
+
+#endif // ^^^ 64-bit ^^^
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __pow5Factor(uint64_t __value) {
+  uint32_t __count = 0;
+  for (;;) {
+    _LIBCPP_ASSERT(__value != 0, "");
+    const uint64_t __q = __div5(__value);
+    const uint32_t __r = static_cast<uint32_t>(__value) - 5 * static_cast<uint32_t>(__q);
+    if (__r != 0) {
+      break;
+    }
+    __value = __q;
+    ++__count;
+  }
+  return __count;
+}
+
+// Returns true if __value is divisible by 5^__p.
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline bool __multipleOfPowerOf5(const uint64_t __value, const uint32_t __p) {
+  // I tried a case distinction on __p, but there was no performance difference.
+  return __pow5Factor(__value) >= __p;
+}
+
+// Returns true if __value is divisible by 2^__p.
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline bool __multipleOfPowerOf2(const uint64_t __value, const uint32_t __p) {
+  _LIBCPP_ASSERT(__value != 0, "");
+  _LIBCPP_ASSERT(__p < 64, "");
+  // __builtin_ctzll doesn't appear to be faster here.
+  return (__value & ((1ull << __p) - 1)) == 0;
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_DS2_INTRINSICS_H

libcxx/src/include/ryu/digit_table.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_DIGIT_TABLE_H
+#define _LIBCPP_SRC_INCLUDE_RYU_DIGIT_TABLE_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// A table of all two-digit numbers. This is used to speed up decimal digit
+// generation by copying pairs of digits into the final output.
+inline constexpr char __DIGIT_TABLE[200] = {
+  '0','0','0','1','0','2','0','3','0','4','0','5','0','6','0','7','0','8','0','9',
+  '1','0','1','1','1','2','1','3','1','4','1','5','1','6','1','7','1','8','1','9',
+  '2','0','2','1','2','2','2','3','2','4','2','5','2','6','2','7','2','8','2','9',
+  '3','0','3','1','3','2','3','3','3','4','3','5','3','6','3','7','3','8','3','9',
+  '4','0','4','1','4','2','4','3','4','4','4','5','4','6','4','7','4','8','4','9',
+  '5','0','5','1','5','2','5','3','5','4','5','5','5','6','5','7','5','8','5','9',
+  '6','0','6','1','6','2','6','3','6','4','6','5','6','6','6','7','6','8','6','9',
+  '7','0','7','1','7','2','7','3','7','4','7','5','7','6','7','7','7','8','7','9',
+  '8','0','8','1','8','2','8','3','8','4','8','5','8','6','8','7','8','8','8','9',
+  '9','0','9','1','9','2','9','3','9','4','9','5','9','6','9','7','9','8','9','9'
+};
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_DIGIT_TABLE_H

libcxx/src/include/ryu/f2s.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_FS2_H
+#define _LIBCPP_SRC_INCLUDE_RYU_FS2_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+[[nodiscard]] to_chars_result __f2s_buffered_n(char* const _First, char* const _Last, const float __f, const chars_format _Fmt);
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_FS2_H

libcxx/src/include/ryu/ryu.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+#ifndef _LIBCPP_SRC_INCLUDE_RYU_RYU_H
+#define _LIBCPP_SRC_INCLUDE_RYU_RYU_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__charconv/chars_format.h"
+#include "__charconv/to_chars_result.h"
+#include "__config"
+#include "__debug"
+#include "__errc"
+#include "cstdint"
+#include "cstring"
+#include "type_traits"
+#include "include/ryu/f2s.h"
+#include "include/ryu/d2s.h"
+#include "include/ryu/d2fixed.h"
+
+#if defined(_M_X64) && defined(_LIBCPP_COMPILER_MSVC)
+#include <intrin0.h> // for _umul128() and __shiftright128()
+#endif // defined(_M_X64) && defined(_LIBCPP_COMPILER_MSVC)
+
+#if defined(_WIN64) || defined(_M_AMD64) || defined(__x86_64__) ||  defined(__aarch64__)
+#define _LIBCPP_64_BIT
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// https://github.com/ulfjack/ryu/tree/59661c3/ryu
+
+#if !defined(_LIBCPP_COMPILER_MSVC)
+_LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward64(unsigned long* __index, unsigned long long __mask) {
+  if (__mask == 0) {
+    return false;
+  }
+  *__index = __builtin_ctzll(__mask);
+  return true;
+}
+
+_LIBCPP_HIDE_FROM_ABI inline unsigned char _BitScanForward(unsigned long* __index, unsigned int __mask) {
+  if (__mask == 0) {
+    return false;
+  }
+  *__index = __builtin_ctz(__mask);
+  return true;
+}
+#endif  // _LIBCPP_COMPILER_MSVC
+
+template <class _Floating>
+[[nodiscard]] to_chars_result _Floating_to_chars_ryu(
+    char* const _First, char* const _Last, const _Floating _Value, const chars_format _Fmt) noexcept {
+    if constexpr (_IsSame<_Floating, float>::value) {
+        return __f2s_buffered_n(_First, _Last, _Value, _Fmt);
+    } else {
+        return __d2s_buffered_n(_First, _Last, _Value, _Fmt);
+    }
+}
+
+template <class _Floating>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_scientific_precision(
+    char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
+
+    // C11 7.21.6.1 "The fprintf function"/5:
+    // "A negative precision argument is taken as if the precision were omitted."
+    // /8: "e,E [...] if the precision is missing, it is taken as 6"
+
+    if (_Precision < 0) {
+        _Precision = 6;
+    } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
+        // _Precision is ok.
+    } else {
+        // Avoid integer overflow.
+        // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
+        return {_Last, errc::value_too_large};
+    }
+
+    return __d2exp_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
+}
+
+template <class _Floating>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI to_chars_result _Floating_to_chars_fixed_precision(
+    char* const _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
+
+    // C11 7.21.6.1 "The fprintf function"/5:
+    // "A negative precision argument is taken as if the precision were omitted."
+    // /8: "f,F [...] If the precision is missing, it is taken as 6"
+
+    if (_Precision < 0) {
+        _Precision = 6;
+    } else if (_Precision < 1'000'000'000) { // Match ' to fix compilation with GCC in C++11 mode
+        // _Precision is ok.
+    } else {
+        // Avoid integer overflow.
+        // (This defensive check is slightly nonconformant; it can be carefully improved in the future.)
+        return {_Last, errc::value_too_large};
+    }
+
+    return __d2fixed_buffered_n(_First, _Last, _Value, static_cast<uint32_t>(_Precision));
+}
+
+#undef _LIBCPP_64_BIT
+#undef _LIBCPP_INTRINSIC128
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on
+
+#endif // _LIBCPP_SRC_INCLUDE_RYU_RYU_H

libcxx/src/include/to_chars_floating_point.h

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// This implementation is dedicated to the memory of Mary and Thavatchai.
+
+#ifndef _LIBCPP_SRC_INCLUDE_TO_CHARS_FLOATING_POINT_H
+#define _LIBCPP_SRC_INCLUDE_TO_CHARS_FLOATING_POINT_H
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__algorithm/find.h"
+#include "__algorithm/find_if.h"
+#include "__algorithm/lower_bound.h"
+#include "__algorithm/min.h"
+#include "__config"
+#include "__iterator/access.h"
+#include "__iterator/size.h"
+#include "bit"
+#include "cfloat"
+#include "climits"
+#include "include/ryu/ryu.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+namespace __itoa {
+inline constexpr char _Charconv_digits[] = {'0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e',
+    'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z'};
+static_assert(_VSTD::size(_Charconv_digits) == 36);
+} // __itoa
+
+// vvvvvvvvvv DERIVED FROM corecrt_internal_fltintrn.h vvvvvvvvvv
+
+template <class _FloatingType>
+struct _Floating_type_traits;
+
+template <>
+struct _Floating_type_traits<float> {
+    static constexpr int32_t _Mantissa_bits = FLT_MANT_DIG;
+    static constexpr int32_t _Exponent_bits = sizeof(float) * CHAR_BIT - FLT_MANT_DIG;
+
+    static constexpr int32_t _Maximum_binary_exponent = FLT_MAX_EXP - 1;
+    static constexpr int32_t _Minimum_binary_exponent = FLT_MIN_EXP - 1;
+
+    static constexpr int32_t _Exponent_bias = 127;
+
+    static constexpr int32_t _Sign_shift     = _Exponent_bits + _Mantissa_bits - 1;
+    static constexpr int32_t _Exponent_shift = _Mantissa_bits - 1;
+
+    using _Uint_type = uint32_t;
+
+    static constexpr uint32_t _Exponent_mask             = (1u << _Exponent_bits) - 1;
+    static constexpr uint32_t _Normal_mantissa_mask      = (1u << _Mantissa_bits) - 1;
+    static constexpr uint32_t _Denormal_mantissa_mask    = (1u << (_Mantissa_bits - 1)) - 1;
+    static constexpr uint32_t _Special_nan_mantissa_mask = 1u << (_Mantissa_bits - 2);
+    static constexpr uint32_t _Shifted_sign_mask         = 1u << _Sign_shift;
+    static constexpr uint32_t _Shifted_exponent_mask     = _Exponent_mask << _Exponent_shift;
+};
+
+template <>
+struct _Floating_type_traits<double> {
+    static constexpr int32_t _Mantissa_bits = DBL_MANT_DIG;
+    static constexpr int32_t _Exponent_bits = sizeof(double) * CHAR_BIT - DBL_MANT_DIG;
+
+    static constexpr int32_t _Maximum_binary_exponent = DBL_MAX_EXP - 1;
+    static constexpr int32_t _Minimum_binary_exponent = DBL_MIN_EXP - 1;
+
+    static constexpr int32_t _Exponent_bias = 1023;
+
+    static constexpr int32_t _Sign_shift     = _Exponent_bits + _Mantissa_bits - 1;
+    static constexpr int32_t _Exponent_shift = _Mantissa_bits - 1;
+
+    using _Uint_type = uint64_t;
+
+    static constexpr uint64_t _Exponent_mask             = (1ULL << _Exponent_bits) - 1;
+    static constexpr uint64_t _Normal_mantissa_mask      = (1ULL << _Mantissa_bits) - 1;
+    static constexpr uint64_t _Denormal_mantissa_mask    = (1ULL << (_Mantissa_bits - 1)) - 1;
+    static constexpr uint64_t _Special_nan_mantissa_mask = 1ULL << (_Mantissa_bits - 2);
+    static constexpr uint64_t _Shifted_sign_mask         = 1ULL << _Sign_shift;
+    static constexpr uint64_t _Shifted_exponent_mask     = _Exponent_mask << _Exponent_shift;
+};
+
+// ^^^^^^^^^^ DERIVED FROM corecrt_internal_fltintrn.h ^^^^^^^^^^
+
+// FUNCTION to_chars (FLOATING-POINT TO STRING)
+template <class _Floating>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
+to_chars_result _Floating_to_chars_hex_precision(
+    char* _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
+
+    // * Determine the effective _Precision.
+    // * Later, we'll decrement _Precision when printing each hexit after the decimal point.
+
+    // The hexits after the decimal point correspond to the explicitly stored fraction bits.
+    // float explicitly stores 23 fraction bits. 23 / 4 == 5.75, which is 6 hexits.
+    // double explicitly stores 52 fraction bits. 52 / 4 == 13, which is 13 hexits.
+    constexpr int _Full_precision         = _IsSame<_Floating, float>::value ? 6 : 13;
+    constexpr int _Adjusted_explicit_bits = _Full_precision * 4;
+
+    if (_Precision < 0) {
+        // C11 7.21.6.1 "The fprintf function"/5: "A negative precision argument is taken as if the precision were
+        // omitted." /8: "if the precision is missing and FLT_RADIX is a power of 2, then the precision is sufficient
+        // for an exact representation of the value"
+        _Precision = _Full_precision;
+    }
+
+    // * Extract the _Ieee_mantissa and _Ieee_exponent.
+    using _Traits    = _Floating_type_traits<_Floating>;
+    using _Uint_type = typename _Traits::_Uint_type;
+
+    const _Uint_type _Uint_value    = _VSTD::bit_cast<_Uint_type>(_Value);
+    const _Uint_type _Ieee_mantissa = _Uint_value & _Traits::_Denormal_mantissa_mask;
+    const int32_t _Ieee_exponent    = static_cast<int32_t>(_Uint_value >> _Traits::_Exponent_shift);
+
+    // * Prepare the _Adjusted_mantissa. This is aligned to hexit boundaries,
+    // * with the implicit bit restored (0 for zero values and subnormal values, 1 for normal values).
+    // * Also calculate the _Unbiased_exponent. This unifies the processing of zero, subnormal, and normal values.
+    _Uint_type _Adjusted_mantissa;
+
+    if constexpr (_IsSame<_Floating, float>::value) {
+        _Adjusted_mantissa = _Ieee_mantissa << 1; // align to hexit boundary (23 isn't divisible by 4)
+    } else {
+        _Adjusted_mantissa = _Ieee_mantissa; // already aligned (52 is divisible by 4)
+    }
+
+    int32_t _Unbiased_exponent;
+
+    if (_Ieee_exponent == 0) { // zero or subnormal
+        // implicit bit is 0
+
+        if (_Ieee_mantissa == 0) { // zero
+            // C11 7.21.6.1 "The fprintf function"/8: "If the value is zero, the exponent is zero."
+            _Unbiased_exponent = 0;
+        } else { // subnormal
+            _Unbiased_exponent = 1 - _Traits::_Exponent_bias;
+        }
+    } else { // normal
+        _Adjusted_mantissa |= _Uint_type{1} << _Adjusted_explicit_bits; // implicit bit is 1
+        _Unbiased_exponent = _Ieee_exponent - _Traits::_Exponent_bias;
+    }
+
+    // _Unbiased_exponent is within [-126, 127] for float, [-1022, 1023] for double.
+
+    // * Decompose _Unbiased_exponent into _Sign_character and _Absolute_exponent.
+    char _Sign_character;
+    uint32_t _Absolute_exponent;
+
+    if (_Unbiased_exponent < 0) {
+        _Sign_character    = '-';
+        _Absolute_exponent = static_cast<uint32_t>(-_Unbiased_exponent);
+    } else {
+        _Sign_character    = '+';
+        _Absolute_exponent = static_cast<uint32_t>(_Unbiased_exponent);
+    }
+
+    // _Absolute_exponent is within [0, 127] for float, [0, 1023] for double.
+
+    // * Perform a single bounds check.
+    {
+        int32_t _Exponent_length;
+
+        if (_Absolute_exponent < 10) {
+            _Exponent_length = 1;
+        } else if (_Absolute_exponent < 100) {
+            _Exponent_length = 2;
+        } else if constexpr (_IsSame<_Floating, float>::value) {
+            _Exponent_length = 3;
+        } else if (_Absolute_exponent < 1000) {
+            _Exponent_length = 3;
+        } else {
+            _Exponent_length = 4;
+        }
+
+        // _Precision might be enormous; avoid integer overflow by testing it separately.
+        ptrdiff_t _Buffer_size = _Last - _First;
+
+        if (_Buffer_size < _Precision) {
+            return {_Last, errc::value_too_large};
+        }
+
+        _Buffer_size -= _Precision;
+
+        const int32_t _Length_excluding_precision = 1 // leading hexit
+                                                    + static_cast<int32_t>(_Precision > 0) // possible decimal point
+                                                    // excluding `+ _Precision`, hexits after decimal point
+                                                    + 2 // "p+" or "p-"
+                                                    + _Exponent_length; // exponent
+
+        if (_Buffer_size < _Length_excluding_precision) {
+            return {_Last, errc::value_too_large};
+        }
+    }
+
+    // * Perform rounding when we've been asked to omit hexits.
+    if (_Precision < _Full_precision) {
+        // _Precision is within [0, 5] for float, [0, 12] for double.
+
+        // _Dropped_bits is within [4, 24] for float, [4, 52] for double.
+        const int _Dropped_bits = (_Full_precision - _Precision) * 4;
+
+        // Perform rounding by adding an appropriately-shifted bit.
+
+        // This can propagate carries all the way into the leading hexit. Examples:
+        // "0.ff9" rounded to a precision of 2 is "1.00".
+        // "1.ff9" rounded to a precision of 2 is "2.00".
+
+        // Note that the leading hexit participates in the rounding decision. Examples:
+        // "0.8" rounded to a precision of 0 is "0".
+        // "1.8" rounded to a precision of 0 is "2".
+
+        // Reference implementation with suboptimal codegen:
+        // bool _Should_round_up(bool _Lsb_bit, bool _Round_bit, bool _Has_tail_bits) {
+        //    // If there are no insignificant set bits, the value is exactly-representable and should not be rounded.
+        //    //
+        //    // If there are insignificant set bits, we need to round according to round_to_nearest.
+        //    // We need to handle two cases: we round up if either [1] the value is slightly greater
+        //    // than the midpoint between two exactly-representable values or [2] the value is exactly the midpoint
+        //    // between two exactly-representable values and the greater of the two is even (this is "round-to-even").
+        //    return _Round_bit && (_Has_tail_bits || _Lsb_bit);
+        //}
+        // const bool _Lsb_bit       = (_Adjusted_mantissa & (_Uint_type{1} << _Dropped_bits)) != 0;
+        // const bool _Round_bit     = (_Adjusted_mantissa & (_Uint_type{1} << (_Dropped_bits - 1))) != 0;
+        // const bool _Has_tail_bits = (_Adjusted_mantissa & ((_Uint_type{1} << (_Dropped_bits - 1)) - 1)) != 0;
+        // const bool _Should_round = _Should_round_up(_Lsb_bit, _Round_bit, _Has_tail_bits);
+        // _Adjusted_mantissa += _Uint_type{_Should_round} << _Dropped_bits;
+
+        // Example for optimized implementation: Let _Dropped_bits be 8.
+        //          Bit index: ...[8]76543210
+        // _Adjusted_mantissa: ...[L]RTTTTTTT (not depicting known details, like hexit alignment)
+        // By focusing on the bit at index _Dropped_bits, we can avoid unnecessary branching and shifting.
+
+        // Bit index: ...[8]76543210
+        //  _Lsb_bit: ...[L]RTTTTTTT
+        const _Uint_type _Lsb_bit = _Adjusted_mantissa;
+
+        //  Bit index: ...9[8]76543210
+        // _Round_bit: ...L[R]TTTTTTT0
+        const _Uint_type _Round_bit = _Adjusted_mantissa << 1;
+
+        // We can detect (without branching) whether any of the trailing bits are set.
+        // Due to _Should_round below, this computation will be used if and only if R is 1, so we can assume that here.
+        //      Bit index: ...9[8]76543210
+        //     _Round_bit: ...L[1]TTTTTTT0
+        // _Has_tail_bits: ....[H]........
+
+        // If all of the trailing bits T are 0, then `_Round_bit - 1` will produce 0 for H (due to R being 1).
+        // If any of the trailing bits T are 1, then `_Round_bit - 1` will produce 1 for H (due to R being 1).
+        const _Uint_type _Has_tail_bits = _Round_bit - 1;
+
+        // Finally, we can use _Should_round_up() logic with bitwise-AND and bitwise-OR,
+        // selecting just the bit at index _Dropped_bits. This is the appropriately-shifted bit that we want.
+        const _Uint_type _Should_round = _Round_bit & (_Has_tail_bits | _Lsb_bit) & (_Uint_type{1} << _Dropped_bits);
+
+        // This rounding technique is dedicated to the memory of Peppermint. =^..^=
+        _Adjusted_mantissa += _Should_round;
+    }
+
+    // * Print the leading hexit, then mask it away.
+    {
+        const uint32_t _Nibble = static_cast<uint32_t>(_Adjusted_mantissa >> _Adjusted_explicit_bits);
+        _LIBCPP_ASSERT(_Nibble < 3, "");
+        const char _Leading_hexit = static_cast<char>('0' + _Nibble);
+
+        *_First++ = _Leading_hexit;
+
+        constexpr _Uint_type _Mask = (_Uint_type{1} << _Adjusted_explicit_bits) - 1;
+        _Adjusted_mantissa &= _Mask;
+    }
+
+    // * Print the decimal point and trailing hexits.
+
+    // C11 7.21.6.1 "The fprintf function"/8:
+    // "if the precision is zero and the # flag is not specified, no decimal-point character appears."
+    if (_Precision > 0) {
+        *_First++ = '.';
+
+        int32_t _Number_of_bits_remaining = _Adjusted_explicit_bits; // 24 for float, 52 for double
+
+        for (;;) {
+            _LIBCPP_ASSERT(_Number_of_bits_remaining >= 4, "");
+            _LIBCPP_ASSERT(_Number_of_bits_remaining % 4 == 0, "");
+            _Number_of_bits_remaining -= 4;
+
+            const uint32_t _Nibble = static_cast<uint32_t>(_Adjusted_mantissa >> _Number_of_bits_remaining);
+            _LIBCPP_ASSERT(_Nibble < 16, "");
+            const char _Hexit = __itoa::_Charconv_digits[_Nibble];
+
+            *_First++ = _Hexit;
+
+            // _Precision is the number of hexits that still need to be printed.
+            --_Precision;
+            if (_Precision == 0) {
+                break; // We're completely done with this phase.
+            }
+            // Otherwise, we need to keep printing hexits.
+
+            if (_Number_of_bits_remaining == 0) {
+                // We've finished printing _Adjusted_mantissa, so all remaining hexits are '0'.
+                _VSTD::memset(_First, '0', static_cast<size_t>(_Precision));
+                _First += _Precision;
+                break;
+            }
+
+            // Mask away the hexit that we just printed, then keep looping.
+            // (We skip this when breaking out of the loop above, because _Adjusted_mantissa isn't used later.)
+            const _Uint_type _Mask = (_Uint_type{1} << _Number_of_bits_remaining) - 1;
+            _Adjusted_mantissa &= _Mask;
+        }
+    }
+
+    // * Print the exponent.
+
+    // C11 7.21.6.1 "The fprintf function"/8: "The exponent always contains at least one digit, and only as many more
+    // digits as necessary to represent the decimal exponent of 2."
+
+    // Performance note: We should take advantage of the known ranges of possible exponents.
+
+    *_First++ = 'p';
+    *_First++ = _Sign_character;
+
+    // We've already printed '-' if necessary, so uint32_t _Absolute_exponent avoids testing that again.
+    return _VSTD::to_chars(_First, _Last, _Absolute_exponent);
+}
+
+template <class _Floating>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
+to_chars_result _Floating_to_chars_hex_shortest(
+    char* _First, char* const _Last, const _Floating _Value) noexcept {
+
+    // This prints "1.728p+0" instead of "2.e5p-1".
+    // This prints "0.000002p-126" instead of "1p-149" for float.
+    // This prints "0.0000000000001p-1022" instead of "1p-1074" for double.
+    // This prioritizes being consistent with printf's de facto behavior (and hex-precision's behavior)
+    // over minimizing the number of characters printed.
+
+    using _Traits    = _Floating_type_traits<_Floating>;
+    using _Uint_type = typename _Traits::_Uint_type;
+
+    const _Uint_type _Uint_value = _VSTD::bit_cast<_Uint_type>(_Value);
+
+    if (_Uint_value == 0) { // zero detected; write "0p+0" and return
+        // C11 7.21.6.1 "The fprintf function"/8: "If the value is zero, the exponent is zero."
+        // Special-casing zero is necessary because of the exponent.
+        const char* const _Str = "0p+0";
+        const size_t _Len      = 4;
+
+        if (_Last - _First < static_cast<ptrdiff_t>(_Len)) {
+            return {_Last, errc::value_too_large};
+        }
+
+        _VSTD::memcpy(_First, _Str, _Len);
+
+        return {_First + _Len, errc{}};
+    }
+
+    const _Uint_type _Ieee_mantissa = _Uint_value & _Traits::_Denormal_mantissa_mask;
+    const int32_t _Ieee_exponent    = static_cast<int32_t>(_Uint_value >> _Traits::_Exponent_shift);
+
+    char _Leading_hexit; // implicit bit
+    int32_t _Unbiased_exponent;
+
+    if (_Ieee_exponent == 0) { // subnormal
+        _Leading_hexit     = '0';
+        _Unbiased_exponent = 1 - _Traits::_Exponent_bias;
+    } else { // normal
+        _Leading_hexit     = '1';
+        _Unbiased_exponent = _Ieee_exponent - _Traits::_Exponent_bias;
+    }
+
+    // Performance note: Consider avoiding per-character bounds checking when there's plenty of space.
+
+    if (_First == _Last) {
+        return {_Last, errc::value_too_large};
+    }
+
+    *_First++ = _Leading_hexit;
+
+    if (_Ieee_mantissa == 0) {
+        // The fraction bits are all 0. Trim them away, including the decimal point.
+    } else {
+        if (_First == _Last) {
+            return {_Last, errc::value_too_large};
+        }
+
+        *_First++ = '.';
+
+        // The hexits after the decimal point correspond to the explicitly stored fraction bits.
+        // float explicitly stores 23 fraction bits. 23 / 4 == 5.75, so we'll print at most 6 hexits.
+        // double explicitly stores 52 fraction bits. 52 / 4 == 13, so we'll print at most 13 hexits.
+        _Uint_type _Adjusted_mantissa;
+        int32_t _Number_of_bits_remaining;
+
+        if constexpr (_IsSame<_Floating, float>::value) {
+            _Adjusted_mantissa        = _Ieee_mantissa << 1; // align to hexit boundary (23 isn't divisible by 4)
+            _Number_of_bits_remaining = 24; // 23 fraction bits + 1 alignment bit
+        } else {
+            _Adjusted_mantissa        = _Ieee_mantissa; // already aligned (52 is divisible by 4)
+            _Number_of_bits_remaining = 52; // 52 fraction bits
+        }
+
+        // do-while: The condition _Adjusted_mantissa != 0 is initially true - we have nonzero fraction bits and we've
+        // printed the decimal point. Each iteration, we print a hexit, mask it away, and keep looping if we still have
+        // nonzero fraction bits. If there would be trailing '0' hexits, this trims them. If there wouldn't be trailing
+        // '0' hexits, the same condition works (as we print the final hexit and mask it away); we don't need to test
+        // _Number_of_bits_remaining.
+        do {
+            _LIBCPP_ASSERT(_Number_of_bits_remaining >= 4, "");
+            _LIBCPP_ASSERT(_Number_of_bits_remaining % 4 == 0, "");
+            _Number_of_bits_remaining -= 4;
+
+            const uint32_t _Nibble = static_cast<uint32_t>(_Adjusted_mantissa >> _Number_of_bits_remaining);
+            _LIBCPP_ASSERT(_Nibble < 16, "");
+            const char _Hexit = __itoa::_Charconv_digits[_Nibble];
+
+            if (_First == _Last) {
+                return {_Last, errc::value_too_large};
+            }
+
+            *_First++ = _Hexit;
+
+            const _Uint_type _Mask = (_Uint_type{1} << _Number_of_bits_remaining) - 1;
+            _Adjusted_mantissa &= _Mask;
+
+        } while (_Adjusted_mantissa != 0);
+    }
+
+    // C11 7.21.6.1 "The fprintf function"/8: "The exponent always contains at least one digit, and only as many more
+    // digits as necessary to represent the decimal exponent of 2."
+
+    // Performance note: We should take advantage of the known ranges of possible exponents.
+
+    // float: _Unbiased_exponent is within [-126, 127].
+    // double: _Unbiased_exponent is within [-1022, 1023].
+
+    if (_Last - _First < 2) {
+        return {_Last, errc::value_too_large};
+    }
+
+    *_First++ = 'p';
+
+    if (_Unbiased_exponent < 0) {
+        *_First++          = '-';
+        _Unbiased_exponent = -_Unbiased_exponent;
+    } else {
+        *_First++ = '+';
+    }
+
+    // We've already printed '-' if necessary, so static_cast<uint32_t> avoids testing that again.
+    return _VSTD::to_chars(_First, _Last, static_cast<uint32_t>(_Unbiased_exponent));
+}
+
+// For general precision, we can use lookup tables to avoid performing trial formatting.
+
+// For a simple example, imagine counting the number of digits D in an integer, and needing to know
+// whether D is less than 3, equal to 3/4/5/6, or greater than 6. We could use a lookup table:
+// D | Largest integer with D digits
+// 2 |      99
+// 3 |     999
+// 4 |   9'999
+// 5 |  99'999
+// 6 | 999'999
+// 7 | table end
+// Looking up an integer in this table with lower_bound() will work:
+// * Too-small integers, like 7, 70, and 99, will cause lower_bound() to return the D == 2 row. (If all we care
+//   about is whether D is less than 3, then it's okay to smash the D == 1 and D == 2 cases together.)
+// * Integers in [100, 999] will cause lower_bound() to return the D == 3 row, and so forth.
+// * Too-large integers, like 1'000'000 and above, will cause lower_bound() to return the end of the table. If we
+//   compute D from that index, this will be considered D == 7, which will activate any "greater than 6" logic.
+
+// Floating-point is slightly more complicated.
+
+// The ordinary lookup tables are for X within [-5, 38] for float, and [-5, 308] for double.
+// (-5 absorbs too-negative exponents, outside the P > X >= -4 criterion. 38 and 308 are the maximum exponents.)
+// Due to the P > X condition, we can use a subset of the table for X within [-5, P - 1], suitably clamped.
+
+// When P is small, rounding can affect X. For example:
+// For P == 1, the largest double with X == 0 is: 9.4999999999999982236431605997495353221893310546875
+// For P == 2, the largest double with X == 0 is: 9.949999999999999289457264239899814128875732421875
+// For P == 3, the largest double with X == 0 is: 9.9949999999999992184029906638897955417633056640625
+
+// Exponent adjustment is a concern for P within [1, 7] for float, and [1, 15] for double (determined via
+// brute force). While larger values of P still perform rounding, they can't trigger exponent adjustment.
+// This is because only values with repeated '9' digits can undergo exponent adjustment during rounding,
+// and floating-point granularity limits the number of consecutive '9' digits that can appear.
+
+// So, we need special lookup tables for small values of P.
+// These tables have varying lengths due to the P > X >= -4 criterion. For example:
+// For P == 1, need table entries for X: -5, -4, -3, -2, -1, 0
+// For P == 2, need table entries for X: -5, -4, -3, -2, -1, 0, 1
+// For P == 3, need table entries for X: -5, -4, -3, -2, -1, 0, 1, 2
+// For P == 4, need table entries for X: -5, -4, -3, -2, -1, 0, 1, 2, 3
+
+// We can concatenate these tables for compact storage, using triangular numbers to access them.
+// The table for P begins at index (P - 1) * (P + 10) / 2 with length P + 5.
+
+// For both the ordinary and special lookup tables, after an index I is returned by lower_bound(), X is I - 5.
+
+// We need to special-case the floating-point value 0.0, which is considered to have X == 0.
+// Otherwise, the lookup tables would consider it to have a highly negative X.
+
+// Finally, because we're working with positive floating-point values,
+// representation comparisons behave identically to floating-point comparisons.
+
+// The following code generated the lookup tables for the scientific exponent X. Don't remove this code.
+#if 0
+// cl /EHsc /nologo /W4 /MT /O2 /std:c++17 generate_tables.cpp && generate_tables
+
+#include <algorithm>
+#include <assert.h>
+#include <charconv>
+#include <cmath>
+#include <limits>
+#include <map>
+#include <stdint.h>
+#include <stdio.h>
+#include <system_error>
+#include <type_traits>
+#include <vector>
+using namespace std;
+
+template <typename UInt, typename Pred>
+[[nodiscard]] UInt uint_partition_point(UInt first, const UInt last, Pred pred) {
+    // Find the beginning of the false partition in [first, last).
+    // [first, last) is partitioned when all of the true values occur before all of the false values.
+
+    static_assert(is_unsigned_v<UInt>);
+    assert(first <= last);
+
+    for (UInt n = last - first; n > 0;) {
+        const UInt n2  = n / 2;
+        const UInt mid = first + n2;
+
+        if (pred(mid)) {
+            first = mid + 1;
+            n     = n - n2 - 1;
+        } else {
+            n = n2;
+        }
+    }
+
+    return first;
+}
+
+template <typename Floating>
+[[nodiscard]] int scientific_exponent_X(const int P, const Floating flt) {
+    char buf[400]; // more than enough
+
+    // C11 7.21.6.1 "The fprintf function"/8 performs trial formatting with scientific precision P - 1.
+    const auto to_result = to_chars(buf, end(buf), flt, chars_format::scientific, P - 1);
+    assert(to_result.ec == errc{});
+
+    const char* exp_ptr = find(buf, to_result.ptr, 'e');
+    assert(exp_ptr != to_result.ptr);
+
+    ++exp_ptr; // advance past 'e'
+
+    if (*exp_ptr == '+') {
+        ++exp_ptr; // advance past '+' which from_chars() won't parse
+    }
+
+    int X;
+    const auto from_result = from_chars(exp_ptr, to_result.ptr, X);
+    assert(from_result.ec == errc{});
+    return X;
+}
+
+template <typename UInt>
+void print_table(const vector<UInt>& v, const char* const name) {
+    constexpr const char* UIntName = _IsSame<UInt, uint32_t>::value ? "uint32_t" : "uint64_t";
+
+    printf("static constexpr %s %s[%zu] = {\n", UIntName, name, v.size());
+
+    for (const auto& val : v) {
+        if constexpr (_IsSame<UInt, uint32_t>::value) {
+            printf("0x%08Xu,\n", val);
+        } else {
+            printf("0x%016llXu,\n", val);
+        }
+    }
+
+    printf("};\n");
+}
+
+enum class Mode { Tables, Tests };
+
+template <typename Floating>
+void generate_tables(const Mode mode) {
+    using Limits = numeric_limits<Floating>;
+    using UInt   = conditional_t<_IsSame<Floating, float>::value, uint32_t, uint64_t>;
+
+    map<int, map<int, UInt>> P_X_LargestValWithX;
+
+    constexpr int MaxP = Limits::max_exponent10 + 1; // MaxP performs no rounding during trial formatting
+
+    for (int P = 1; P <= MaxP; ++P) {
+        for (int X = -5; X < P; ++X) {
+            constexpr Floating first = static_cast<Floating>(9e-5); // well below 9.5e-5, otherwise arbitrary
+            constexpr Floating last  = Limits::infinity(); // one bit above Limits::max()
+
+            const UInt val_beyond_X = uint_partition_point(reinterpret_cast<const UInt&>(first),
+                reinterpret_cast<const UInt&>(last),
+                [P, X](const UInt u) { return scientific_exponent_X(P, reinterpret_cast<const Floating&>(u)) <= X; });
+
+            P_X_LargestValWithX[P][X] = val_beyond_X - 1;
+        }
+    }
+
+    constexpr const char* FloatingName = _IsSame<Floating, float>::value ? "float" : "double";
+
+    constexpr int MaxSpecialP = _IsSame<Floating, float>::value ? 7 : 15; // MaxSpecialP is affected by exponent adjustment
+
+    if (mode == Mode::Tables) {
+        printf("template <>\n");
+        printf("struct _General_precision_tables<%s> {\n", FloatingName);
+
+        printf("static constexpr int _Max_special_P = %d;\n", MaxSpecialP);
+
+        vector<UInt> special;
+
+        for (int P = 1; P <= MaxSpecialP; ++P) {
+            for (int X = -5; X < P; ++X) {
+                const UInt val = P_X_LargestValWithX[P][X];
+                special.push_back(val);
+            }
+        }
+
+        print_table(special, "_Special_X_table");
+
+        for (int P = MaxSpecialP + 1; P < MaxP; ++P) {
+            for (int X = -5; X < P; ++X) {
+                const UInt val = P_X_LargestValWithX[P][X];
+                assert(val == P_X_LargestValWithX[MaxP][X]);
+            }
+        }
+
+        printf("static constexpr int _Max_P = %d;\n", MaxP);
+
+        vector<UInt> ordinary;
+
+        for (int X = -5; X < MaxP; ++X) {
+            const UInt val = P_X_LargestValWithX[MaxP][X];
+            ordinary.push_back(val);
+        }
+
+        print_table(ordinary, "_Ordinary_X_table");
+
+        printf("};\n");
+    } else {
+        printf("==========\n");
+        printf("Test cases for %s:\n", FloatingName);
+
+        constexpr int Hexits         = _IsSame<Floating, float>::value ? 6 : 13;
+        constexpr const char* Suffix = _IsSame<Floating, float>::value ? "f" : "";
+
+        for (int P = 1; P <= MaxP; ++P) {
+            for (int X = -5; X < P; ++X) {
+                if (P <= MaxSpecialP || P == 25 || P == MaxP || X == P - 1) {
+                    const UInt val1   = P_X_LargestValWithX[P][X];
+                    const Floating f1 = reinterpret_cast<const Floating&>(val1);
+                    const UInt val2   = val1 + 1;
+                    const Floating f2 = reinterpret_cast<const Floating&>(val2);
+
+                    printf("{%.*a%s, chars_format::general, %d, \"%.*g\"},\n", Hexits, f1, Suffix, P, P, f1);
+                    if (isfinite(f2)) {
+                        printf("{%.*a%s, chars_format::general, %d, \"%.*g\"},\n", Hexits, f2, Suffix, P, P, f2);
+                    }
+                }
+            }
+        }
+    }
+}
+
+int main() {
+    printf("template <class _Floating>\n");
+    printf("struct _General_precision_tables;\n");
+    generate_tables<float>(Mode::Tables);
+    generate_tables<double>(Mode::Tables);
+    generate_tables<float>(Mode::Tests);
+    generate_tables<double>(Mode::Tests);
+}
+#endif // 0
+
+template <class _Floating>
+struct _General_precision_tables;
+
+template <>
+struct _General_precision_tables<float> {
+    static constexpr int _Max_special_P = 7;
+
+    static constexpr uint32_t _Special_X_table[63] = {0x38C73ABCu, 0x3A79096Bu, 0x3C1BA5E3u, 0x3DC28F5Cu, 0x3F733333u,
+        0x4117FFFFu, 0x38D0AAA7u, 0x3A826AA8u, 0x3C230553u, 0x3DCBC6A7u, 0x3F7EB851u, 0x411F3333u, 0x42C6FFFFu,
+        0x38D19C3Fu, 0x3A8301A7u, 0x3C23C211u, 0x3DCCB295u, 0x3F7FDF3Bu, 0x411FEB85u, 0x42C7E666u, 0x4479DFFFu,
+        0x38D1B468u, 0x3A8310C1u, 0x3C23D4F1u, 0x3DCCCA2Du, 0x3F7FFCB9u, 0x411FFDF3u, 0x42C7FD70u, 0x4479FCCCu,
+        0x461C3DFFu, 0x38D1B6D2u, 0x3A831243u, 0x3C23D6D4u, 0x3DCCCC89u, 0x3F7FFFACu, 0x411FFFCBu, 0x42C7FFBEu,
+        0x4479FFAEu, 0x461C3FCCu, 0x47C34FBFu, 0x38D1B710u, 0x3A83126Au, 0x3C23D704u, 0x3DCCCCC6u, 0x3F7FFFF7u,
+        0x411FFFFAu, 0x42C7FFF9u, 0x4479FFF7u, 0x461C3FFAu, 0x47C34FF9u, 0x497423F7u, 0x38D1B716u, 0x3A83126Eu,
+        0x3C23D709u, 0x3DCCCCCCu, 0x3F7FFFFFu, 0x411FFFFFu, 0x42C7FFFFu, 0x4479FFFFu, 0x461C3FFFu, 0x47C34FFFu,
+        0x497423FFu, 0x4B18967Fu};
+
+    static constexpr int _Max_P = 39;
+
+    static constexpr uint32_t _Ordinary_X_table[44] = {0x38D1B717u, 0x3A83126Eu, 0x3C23D70Au, 0x3DCCCCCCu, 0x3F7FFFFFu,
+        0x411FFFFFu, 0x42C7FFFFu, 0x4479FFFFu, 0x461C3FFFu, 0x47C34FFFu, 0x497423FFu, 0x4B18967Fu, 0x4CBEBC1Fu,
+        0x4E6E6B27u, 0x501502F8u, 0x51BA43B7u, 0x5368D4A5u, 0x551184E7u, 0x56B5E620u, 0x58635FA9u, 0x5A0E1BC9u,
+        0x5BB1A2BCu, 0x5D5E0B6Bu, 0x5F0AC723u, 0x60AD78EBu, 0x6258D726u, 0x64078678u, 0x65A96816u, 0x6753C21Bu,
+        0x69045951u, 0x6AA56FA5u, 0x6C4ECB8Fu, 0x6E013F39u, 0x6FA18F07u, 0x7149F2C9u, 0x72FC6F7Cu, 0x749DC5ADu,
+        0x76453719u, 0x77F684DFu, 0x799A130Bu, 0x7B4097CEu, 0x7CF0BDC2u, 0x7E967699u, 0x7F7FFFFFu};
+};
+
+template <>
+struct _General_precision_tables<double> {
+    static constexpr int _Max_special_P = 15;
+
+    static constexpr uint64_t _Special_X_table[195] = {0x3F18E757928E0C9Du, 0x3F4F212D77318FC5u, 0x3F8374BC6A7EF9DBu,
+        0x3FB851EB851EB851u, 0x3FEE666666666666u, 0x4022FFFFFFFFFFFFu, 0x3F1A1554FBDAD751u, 0x3F504D551D68C692u,
+        0x3F8460AA64C2F837u, 0x3FB978D4FDF3B645u, 0x3FEFD70A3D70A3D7u, 0x4023E66666666666u, 0x4058DFFFFFFFFFFFu,
+        0x3F1A3387ECC8EB96u, 0x3F506034F3FD933Eu, 0x3F84784230FCF80Du, 0x3FB99652BD3C3611u, 0x3FEFFBE76C8B4395u,
+        0x4023FD70A3D70A3Du, 0x4058FCCCCCCCCCCCu, 0x408F3BFFFFFFFFFFu, 0x3F1A368D04E0BA6Au, 0x3F506218230C7482u,
+        0x3F847A9E2BCF91A3u, 0x3FB99945B6C3760Bu, 0x3FEFFF972474538Eu, 0x4023FFBE76C8B439u, 0x4058FFAE147AE147u,
+        0x408F3F9999999999u, 0x40C387BFFFFFFFFFu, 0x3F1A36DA54164F19u, 0x3F506248748DF16Fu, 0x3F847ADA91B16DCBu,
+        0x3FB99991361DC93Eu, 0x3FEFFFF583A53B8Eu, 0x4023FFF972474538u, 0x4058FFF7CED91687u, 0x408F3FF5C28F5C28u,
+        0x40C387F999999999u, 0x40F869F7FFFFFFFFu, 0x3F1A36E20F35445Du, 0x3F50624D49814ABAu, 0x3F847AE09BE19D69u,
+        0x3FB99998C2DA04C3u, 0x3FEFFFFEF39085F4u, 0x4023FFFF583A53B8u, 0x4058FFFF2E48E8A7u, 0x408F3FFEF9DB22D0u,
+        0x40C387FF5C28F5C2u, 0x40F869FF33333333u, 0x412E847EFFFFFFFFu, 0x3F1A36E2D51EC34Bu, 0x3F50624DC5333A0Eu,
+        0x3F847AE136800892u, 0x3FB9999984200AB7u, 0x3FEFFFFFE5280D65u, 0x4023FFFFEF39085Fu, 0x4058FFFFEB074A77u,
+        0x408F3FFFE5C91D14u, 0x40C387FFEF9DB22Du, 0x40F869FFEB851EB8u, 0x412E847FE6666666u, 0x416312CFEFFFFFFFu,
+        0x3F1A36E2E8E94FFCu, 0x3F50624DD191D1FDu, 0x3F847AE145F6467Du, 0x3FB999999773D81Cu, 0x3FEFFFFFFD50CE23u,
+        0x4023FFFFFE5280D6u, 0x4058FFFFFDE7210Bu, 0x408F3FFFFD60E94Eu, 0x40C387FFFE5C91D1u, 0x40F869FFFDF3B645u,
+        0x412E847FFD70A3D7u, 0x416312CFFE666666u, 0x4197D783FDFFFFFFu, 0x3F1A36E2EAE3F7A7u, 0x3F50624DD2CE7AC8u,
+        0x3F847AE14782197Bu, 0x3FB9999999629FD9u, 0x3FEFFFFFFFBB47D0u, 0x4023FFFFFFD50CE2u, 0x4058FFFFFFCA501Au,
+        0x408F3FFFFFBCE421u, 0x40C387FFFFD60E94u, 0x40F869FFFFCB923Au, 0x412E847FFFBE76C8u, 0x416312CFFFD70A3Du,
+        0x4197D783FFCCCCCCu, 0x41CDCD64FFBFFFFFu, 0x3F1A36E2EB16A205u, 0x3F50624DD2EE2543u, 0x3F847AE147A9AE94u,
+        0x3FB9999999941A39u, 0x3FEFFFFFFFF920C8u, 0x4023FFFFFFFBB47Du, 0x4058FFFFFFFAA19Cu, 0x408F3FFFFFF94A03u,
+        0x40C387FFFFFBCE42u, 0x40F869FFFFFAC1D2u, 0x412E847FFFF97247u, 0x416312CFFFFBE76Cu, 0x4197D783FFFAE147u,
+        0x41CDCD64FFF99999u, 0x4202A05F1FFBFFFFu, 0x3F1A36E2EB1BB30Fu, 0x3F50624DD2F14FE9u, 0x3F847AE147ADA3E3u,
+        0x3FB9999999990CDCu, 0x3FEFFFFFFFFF5014u, 0x4023FFFFFFFF920Cu, 0x4058FFFFFFFF768Fu, 0x408F3FFFFFFF5433u,
+        0x40C387FFFFFF94A0u, 0x40F869FFFFFF79C8u, 0x412E847FFFFF583Au, 0x416312CFFFFF9724u, 0x4197D783FFFF7CEDu,
+        0x41CDCD64FFFF5C28u, 0x4202A05F1FFF9999u, 0x42374876E7FF7FFFu, 0x3F1A36E2EB1C34C3u, 0x3F50624DD2F1A0FAu,
+        0x3F847AE147AE0938u, 0x3FB9999999998B86u, 0x3FEFFFFFFFFFEE68u, 0x4023FFFFFFFFF501u, 0x4058FFFFFFFFF241u,
+        0x408F3FFFFFFFEED1u, 0x40C387FFFFFFF543u, 0x40F869FFFFFFF294u, 0x412E847FFFFFEF39u, 0x416312CFFFFFF583u,
+        0x4197D783FFFFF2E4u, 0x41CDCD64FFFFEF9Du, 0x4202A05F1FFFF5C2u, 0x42374876E7FFF333u, 0x426D1A94A1FFEFFFu,
+        0x3F1A36E2EB1C41BBu, 0x3F50624DD2F1A915u, 0x3F847AE147AE135Au, 0x3FB9999999999831u, 0x3FEFFFFFFFFFFE3Du,
+        0x4023FFFFFFFFFEE6u, 0x4058FFFFFFFFFEA0u, 0x408F3FFFFFFFFE48u, 0x40C387FFFFFFFEEDu, 0x40F869FFFFFFFEA8u,
+        0x412E847FFFFFFE52u, 0x416312CFFFFFFEF3u, 0x4197D783FFFFFEB0u, 0x41CDCD64FFFFFE5Cu, 0x4202A05F1FFFFEF9u,
+        0x42374876E7FFFEB8u, 0x426D1A94A1FFFE66u, 0x42A2309CE53FFEFFu, 0x3F1A36E2EB1C4307u, 0x3F50624DD2F1A9E4u,
+        0x3F847AE147AE145Eu, 0x3FB9999999999975u, 0x3FEFFFFFFFFFFFD2u, 0x4023FFFFFFFFFFE3u, 0x4058FFFFFFFFFFDCu,
+        0x408F3FFFFFFFFFD4u, 0x40C387FFFFFFFFE4u, 0x40F869FFFFFFFFDDu, 0x412E847FFFFFFFD5u, 0x416312CFFFFFFFE5u,
+        0x4197D783FFFFFFDEu, 0x41CDCD64FFFFFFD6u, 0x4202A05F1FFFFFE5u, 0x42374876E7FFFFDFu, 0x426D1A94A1FFFFD7u,
+        0x42A2309CE53FFFE6u, 0x42D6BCC41E8FFFDFu, 0x3F1A36E2EB1C4328u, 0x3F50624DD2F1A9F9u, 0x3F847AE147AE1477u,
+        0x3FB9999999999995u, 0x3FEFFFFFFFFFFFFBu, 0x4023FFFFFFFFFFFDu, 0x4058FFFFFFFFFFFCu, 0x408F3FFFFFFFFFFBu,
+        0x40C387FFFFFFFFFDu, 0x40F869FFFFFFFFFCu, 0x412E847FFFFFFFFBu, 0x416312CFFFFFFFFDu, 0x4197D783FFFFFFFCu,
+        0x41CDCD64FFFFFFFBu, 0x4202A05F1FFFFFFDu, 0x42374876E7FFFFFCu, 0x426D1A94A1FFFFFBu, 0x42A2309CE53FFFFDu,
+        0x42D6BCC41E8FFFFCu, 0x430C6BF52633FFFBu};
+
+    static constexpr int _Max_P = 309;
+
+    static constexpr uint64_t _Ordinary_X_table[314] = {0x3F1A36E2EB1C432Cu, 0x3F50624DD2F1A9FBu, 0x3F847AE147AE147Au,
+        0x3FB9999999999999u, 0x3FEFFFFFFFFFFFFFu, 0x4023FFFFFFFFFFFFu, 0x4058FFFFFFFFFFFFu, 0x408F3FFFFFFFFFFFu,
+        0x40C387FFFFFFFFFFu, 0x40F869FFFFFFFFFFu, 0x412E847FFFFFFFFFu, 0x416312CFFFFFFFFFu, 0x4197D783FFFFFFFFu,
+        0x41CDCD64FFFFFFFFu, 0x4202A05F1FFFFFFFu, 0x42374876E7FFFFFFu, 0x426D1A94A1FFFFFFu, 0x42A2309CE53FFFFFu,
+        0x42D6BCC41E8FFFFFu, 0x430C6BF52633FFFFu, 0x4341C37937E07FFFu, 0x4376345785D89FFFu, 0x43ABC16D674EC7FFu,
+        0x43E158E460913CFFu, 0x4415AF1D78B58C3Fu, 0x444B1AE4D6E2EF4Fu, 0x4480F0CF064DD591u, 0x44B52D02C7E14AF6u,
+        0x44EA784379D99DB4u, 0x45208B2A2C280290u, 0x4554ADF4B7320334u, 0x4589D971E4FE8401u, 0x45C027E72F1F1281u,
+        0x45F431E0FAE6D721u, 0x46293E5939A08CE9u, 0x465F8DEF8808B024u, 0x4693B8B5B5056E16u, 0x46C8A6E32246C99Cu,
+        0x46FED09BEAD87C03u, 0x4733426172C74D82u, 0x476812F9CF7920E2u, 0x479E17B84357691Bu, 0x47D2CED32A16A1B1u,
+        0x48078287F49C4A1Du, 0x483D6329F1C35CA4u, 0x48725DFA371A19E6u, 0x48A6F578C4E0A060u, 0x48DCB2D6F618C878u,
+        0x4911EFC659CF7D4Bu, 0x49466BB7F0435C9Eu, 0x497C06A5EC5433C6u, 0x49B18427B3B4A05Bu, 0x49E5E531A0A1C872u,
+        0x4A1B5E7E08CA3A8Fu, 0x4A511B0EC57E6499u, 0x4A8561D276DDFDC0u, 0x4ABABA4714957D30u, 0x4AF0B46C6CDD6E3Eu,
+        0x4B24E1878814C9CDu, 0x4B5A19E96A19FC40u, 0x4B905031E2503DA8u, 0x4BC4643E5AE44D12u, 0x4BF97D4DF19D6057u,
+        0x4C2FDCA16E04B86Du, 0x4C63E9E4E4C2F344u, 0x4C98E45E1DF3B015u, 0x4CCF1D75A5709C1Au, 0x4D03726987666190u,
+        0x4D384F03E93FF9F4u, 0x4D6E62C4E38FF872u, 0x4DA2FDBB0E39FB47u, 0x4DD7BD29D1C87A19u, 0x4E0DAC74463A989Fu,
+        0x4E428BC8ABE49F63u, 0x4E772EBAD6DDC73Cu, 0x4EACFA698C95390Bu, 0x4EE21C81F7DD43A7u, 0x4F16A3A275D49491u,
+        0x4F4C4C8B1349B9B5u, 0x4F81AFD6EC0E1411u, 0x4FB61BCCA7119915u, 0x4FEBA2BFD0D5FF5Bu, 0x502145B7E285BF98u,
+        0x50559725DB272F7Fu, 0x508AFCEF51F0FB5Eu, 0x50C0DE1593369D1Bu, 0x50F5159AF8044462u, 0x512A5B01B605557Au,
+        0x516078E111C3556Cu, 0x5194971956342AC7u, 0x51C9BCDFABC13579u, 0x5200160BCB58C16Cu, 0x52341B8EBE2EF1C7u,
+        0x526922726DBAAE39u, 0x529F6B0F092959C7u, 0x52D3A2E965B9D81Cu, 0x53088BA3BF284E23u, 0x533EAE8CAEF261ACu,
+        0x53732D17ED577D0Bu, 0x53A7F85DE8AD5C4Eu, 0x53DDF67562D8B362u, 0x5412BA095DC7701Du, 0x5447688BB5394C25u,
+        0x547D42AEA2879F2Eu, 0x54B249AD2594C37Cu, 0x54E6DC186EF9F45Cu, 0x551C931E8AB87173u, 0x5551DBF316B346E7u,
+        0x558652EFDC6018A1u, 0x55BBE7ABD3781ECAu, 0x55F170CB642B133Eu, 0x5625CCFE3D35D80Eu, 0x565B403DCC834E11u,
+        0x569108269FD210CBu, 0x56C54A3047C694FDu, 0x56FA9CBC59B83A3Du, 0x5730A1F5B8132466u, 0x5764CA732617ED7Fu,
+        0x5799FD0FEF9DE8DFu, 0x57D03E29F5C2B18Bu, 0x58044DB473335DEEu, 0x583961219000356Au, 0x586FB969F40042C5u,
+        0x58A3D3E2388029BBu, 0x58D8C8DAC6A0342Au, 0x590EFB1178484134u, 0x59435CEAEB2D28C0u, 0x59783425A5F872F1u,
+        0x59AE412F0F768FADu, 0x59E2E8BD69AA19CCu, 0x5A17A2ECC414A03Fu, 0x5A4D8BA7F519C84Fu, 0x5A827748F9301D31u,
+        0x5AB7151B377C247Eu, 0x5AECDA62055B2D9Du, 0x5B22087D4358FC82u, 0x5B568A9C942F3BA3u, 0x5B8C2D43B93B0A8Bu,
+        0x5BC19C4A53C4E697u, 0x5BF6035CE8B6203Du, 0x5C2B843422E3A84Cu, 0x5C6132A095CE492Fu, 0x5C957F48BB41DB7Bu,
+        0x5CCADF1AEA12525Au, 0x5D00CB70D24B7378u, 0x5D34FE4D06DE5056u, 0x5D6A3DE04895E46Cu, 0x5DA066AC2D5DAEC3u,
+        0x5DD4805738B51A74u, 0x5E09A06D06E26112u, 0x5E400444244D7CABu, 0x5E7405552D60DBD6u, 0x5EA906AA78B912CBu,
+        0x5EDF485516E7577Eu, 0x5F138D352E5096AFu, 0x5F48708279E4BC5Au, 0x5F7E8CA3185DEB71u, 0x5FB317E5EF3AB327u,
+        0x5FE7DDDF6B095FF0u, 0x601DD55745CBB7ECu, 0x6052A5568B9F52F4u, 0x60874EAC2E8727B1u, 0x60BD22573A28F19Du,
+        0x60F2357684599702u, 0x6126C2D4256FFCC2u, 0x615C73892ECBFBF3u, 0x6191C835BD3F7D78u, 0x61C63A432C8F5CD6u,
+        0x61FBC8D3F7B3340Bu, 0x62315D847AD00087u, 0x6265B4E5998400A9u, 0x629B221EFFE500D3u, 0x62D0F5535FEF2084u,
+        0x630532A837EAE8A5u, 0x633A7F5245E5A2CEu, 0x63708F936BAF85C1u, 0x63A4B378469B6731u, 0x63D9E056584240FDu,
+        0x64102C35F729689Eu, 0x6444374374F3C2C6u, 0x647945145230B377u, 0x64AF965966BCE055u, 0x64E3BDF7E0360C35u,
+        0x6518AD75D8438F43u, 0x654ED8D34E547313u, 0x6583478410F4C7ECu, 0x65B819651531F9E7u, 0x65EE1FBE5A7E7861u,
+        0x6622D3D6F88F0B3Cu, 0x665788CCB6B2CE0Cu, 0x668D6AFFE45F818Fu, 0x66C262DFEEBBB0F9u, 0x66F6FB97EA6A9D37u,
+        0x672CBA7DE5054485u, 0x6761F48EAF234AD3u, 0x679671B25AEC1D88u, 0x67CC0E1EF1A724EAu, 0x680188D357087712u,
+        0x6835EB082CCA94D7u, 0x686B65CA37FD3A0Du, 0x68A11F9E62FE4448u, 0x68D56785FBBDD55Au, 0x690AC1677AAD4AB0u,
+        0x6940B8E0ACAC4EAEu, 0x6974E718D7D7625Au, 0x69AA20DF0DCD3AF0u, 0x69E0548B68A044D6u, 0x6A1469AE42C8560Cu,
+        0x6A498419D37A6B8Fu, 0x6A7FE52048590672u, 0x6AB3EF342D37A407u, 0x6AE8EB0138858D09u, 0x6B1F25C186A6F04Cu,
+        0x6B537798F428562Fu, 0x6B88557F31326BBBu, 0x6BBE6ADEFD7F06AAu, 0x6BF302CB5E6F642Au, 0x6C27C37E360B3D35u,
+        0x6C5DB45DC38E0C82u, 0x6C9290BA9A38C7D1u, 0x6CC734E940C6F9C5u, 0x6CFD022390F8B837u, 0x6D3221563A9B7322u,
+        0x6D66A9ABC9424FEBu, 0x6D9C5416BB92E3E6u, 0x6DD1B48E353BCE6Fu, 0x6E0621B1C28AC20Bu, 0x6E3BAA1E332D728Eu,
+        0x6E714A52DFFC6799u, 0x6EA59CE797FB817Fu, 0x6EDB04217DFA61DFu, 0x6F10E294EEBC7D2Bu, 0x6F451B3A2A6B9C76u,
+        0x6F7A6208B5068394u, 0x6FB07D457124123Cu, 0x6FE49C96CD6D16CBu, 0x7019C3BC80C85C7Eu, 0x70501A55D07D39CFu,
+        0x708420EB449C8842u, 0x70B9292615C3AA53u, 0x70EF736F9B3494E8u, 0x7123A825C100DD11u, 0x7158922F31411455u,
+        0x718EB6BAFD91596Bu, 0x71C33234DE7AD7E2u, 0x71F7FEC216198DDBu, 0x722DFE729B9FF152u, 0x7262BF07A143F6D3u,
+        0x72976EC98994F488u, 0x72CD4A7BEBFA31AAu, 0x73024E8D737C5F0Au, 0x7336E230D05B76CDu, 0x736C9ABD04725480u,
+        0x73A1E0B622C774D0u, 0x73D658E3AB795204u, 0x740BEF1C9657A685u, 0x74417571DDF6C813u, 0x7475D2CE55747A18u,
+        0x74AB4781EAD1989Eu, 0x74E10CB132C2FF63u, 0x75154FDD7F73BF3Bu, 0x754AA3D4DF50AF0Au, 0x7580A6650B926D66u,
+        0x75B4CFFE4E7708C0u, 0x75EA03FDE214CAF0u, 0x7620427EAD4CFED6u, 0x7654531E58A03E8Bu, 0x768967E5EEC84E2Eu,
+        0x76BFC1DF6A7A61BAu, 0x76F3D92BA28C7D14u, 0x7728CF768B2F9C59u, 0x775F03542DFB8370u, 0x779362149CBD3226u,
+        0x77C83A99C3EC7EAFu, 0x77FE494034E79E5Bu, 0x7832EDC82110C2F9u, 0x7867A93A2954F3B7u, 0x789D9388B3AA30A5u,
+        0x78D27C35704A5E67u, 0x79071B42CC5CF601u, 0x793CE2137F743381u, 0x79720D4C2FA8A030u, 0x79A6909F3B92C83Du,
+        0x79DC34C70A777A4Cu, 0x7A11A0FC668AAC6Fu, 0x7A46093B802D578Bu, 0x7A7B8B8A6038AD6Eu, 0x7AB137367C236C65u,
+        0x7AE585041B2C477Eu, 0x7B1AE64521F7595Eu, 0x7B50CFEB353A97DAu, 0x7B8503E602893DD1u, 0x7BBA44DF832B8D45u,
+        0x7BF06B0BB1FB384Bu, 0x7C2485CE9E7A065Eu, 0x7C59A742461887F6u, 0x7C9008896BCF54F9u, 0x7CC40AABC6C32A38u,
+        0x7CF90D56B873F4C6u, 0x7D2F50AC6690F1F8u, 0x7D63926BC01A973Bu, 0x7D987706B0213D09u, 0x7DCE94C85C298C4Cu,
+        0x7E031CFD3999F7AFu, 0x7E37E43C8800759Bu, 0x7E6DDD4BAA009302u, 0x7EA2AA4F4A405BE1u, 0x7ED754E31CD072D9u,
+        0x7F0D2A1BE4048F90u, 0x7F423A516E82D9BAu, 0x7F76C8E5CA239028u, 0x7FAC7B1F3CAC7433u, 0x7FE1CCF385EBC89Fu,
+        0x7FEFFFFFFFFFFFFFu};
+};
+
+template <class _Floating>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
+to_chars_result _Floating_to_chars_general_precision(
+    char* _First, char* const _Last, const _Floating _Value, int _Precision) noexcept {
+
+    using _Traits    = _Floating_type_traits<_Floating>;
+    using _Uint_type = typename _Traits::_Uint_type;
+
+    const _Uint_type _Uint_value = _VSTD::bit_cast<_Uint_type>(_Value);
+
+    if (_Uint_value == 0) { // zero detected; write "0" and return; _Precision is irrelevant due to zero-trimming
+        if (_First == _Last) {
+            return {_Last, errc::value_too_large};
+        }
+
+        *_First++ = '0';
+
+        return {_First, errc{}};
+    }
+
+    // C11 7.21.6.1 "The fprintf function"/5:
+    // "A negative precision argument is taken as if the precision were omitted."
+    // /8: "g,G [...] Let P equal the precision if nonzero, 6 if the precision is omitted,
+    // or 1 if the precision is zero."
+
+    // Performance note: It's possible to rewrite this for branchless codegen,
+    // but profiling will be necessary to determine whether that's faster.
+    if (_Precision < 0) {
+        _Precision = 6;
+    } else if (_Precision == 0) {
+        _Precision = 1;
+    } else if (_Precision < 1'000'000) {
+        // _Precision is ok.
+    } else {
+        // Avoid integer overflow.
+        // Due to general notation's zero-trimming behavior, we can simply clamp _Precision.
+        // This is further clamped below.
+        _Precision = 1'000'000;
+    }
+
+    // _Precision is now the Standard's P.
+
+    // /8: "Then, if a conversion with style E would have an exponent of X:
+    // - if P > X >= -4, the conversion is with style f (or F) and precision P - (X + 1).
+    // - otherwise, the conversion is with style e (or E) and precision P - 1."
+
+    // /8: "Finally, [...] any trailing zeros are removed from the fractional portion of the result
+    // and the decimal-point character is removed if there is no fractional portion remaining."
+
+    using _Tables = _General_precision_tables<_Floating>;
+
+    const _Uint_type* _Table_begin;
+    const _Uint_type* _Table_end;
+
+    if (_Precision <= _Tables::_Max_special_P) {
+        _Table_begin = _Tables::_Special_X_table + (_Precision - 1) * (_Precision + 10) / 2;
+        _Table_end   = _Table_begin + _Precision + 5;
+    } else {
+        _Table_begin = _Tables::_Ordinary_X_table;
+        _Table_end   = _Table_begin + _VSTD::min(_Precision, _Tables::_Max_P) + 5;
+    }
+
+    // Profiling indicates that linear search is faster than binary search for small tables.
+    // Performance note: lambda captures may have a small performance cost.
+    const _Uint_type* const _Table_lower_bound = [=] {
+        if constexpr (!_IsSame<_Floating, float>::value) {
+            if (_Precision > 155) { // threshold determined via profiling
+                return _VSTD::lower_bound(_Table_begin, _Table_end, _Uint_value, less{});
+            }
+        }
+
+        return _VSTD::find_if(_Table_begin, _Table_end, [=](const _Uint_type _Elem) { return _Uint_value <= _Elem; });
+    }();
+
+    const ptrdiff_t _Table_index     = _Table_lower_bound - _Table_begin;
+    const int _Scientific_exponent_X = static_cast<int>(_Table_index - 5);
+    const bool _Use_fixed_notation   = _Precision > _Scientific_exponent_X && _Scientific_exponent_X >= -4;
+
+    // Performance note: it might (or might not) be faster to modify Ryu Printf to perform zero-trimming.
+    // Such modifications would involve a fairly complicated state machine (notably, both '0' and '9' digits would
+    // need to be buffered, due to rounding), and that would have performance costs due to increased branching.
+    // Here, we're using a simpler approach: writing into a local buffer, manually zero-trimming, and then copying into
+    // the output range. The necessary buffer size is reasonably small, the zero-trimming logic is simple and fast,
+    // and the final copying is also fast.
+
+    constexpr int _Max_output_length =
+        _IsSame<_Floating, float>::value ? 117 : 773; // cases: 0x1.fffffep-126f and 0x1.fffffffffffffp-1022
+    constexpr int _Max_fixed_precision =
+        _IsSame<_Floating, float>::value ? 37 : 66; // cases: 0x1.fffffep-14f and 0x1.fffffffffffffp-14
+    constexpr int _Max_scientific_precision =
+        _IsSame<_Floating, float>::value ? 111 : 766; // cases: 0x1.fffffep-126f and 0x1.fffffffffffffp-1022
+
+    // Note that _Max_output_length is determined by scientific notation and is more than enough for fixed notation.
+    // 0x1.fffffep+127f is 39 digits, plus 1 for '.', plus _Max_fixed_precision for '0' digits, equals 77.
+    // 0x1.fffffffffffffp+1023 is 309 digits, plus 1 for '.', plus _Max_fixed_precision for '0' digits, equals 376.
+
+    char _Buffer[_Max_output_length];
+    const char* const _Significand_first = _Buffer; // e.g. "1.234"
+    const char* _Significand_last        = nullptr;
+    const char* _Exponent_first          = nullptr; // e.g. "e-05"
+    const char* _Exponent_last           = nullptr;
+    int _Effective_precision; // number of digits printed after the decimal point, before trimming
+
+    // Write into the local buffer.
+    // Clamping _Effective_precision allows _Buffer to be as small as possible, and increases efficiency.
+    if (_Use_fixed_notation) {
+        _Effective_precision = _VSTD::min(_Precision - (_Scientific_exponent_X + 1), _Max_fixed_precision);
+        const to_chars_result _Buf_result =
+            _Floating_to_chars_fixed_precision(_Buffer, _VSTD::end(_Buffer), _Value, _Effective_precision);
+        _LIBCPP_ASSERT(_Buf_result.ec == errc{}, "");
+        _Significand_last = _Buf_result.ptr;
+    } else {
+        _Effective_precision = _VSTD::min(_Precision - 1, _Max_scientific_precision);
+        const to_chars_result _Buf_result =
+            _Floating_to_chars_scientific_precision(_Buffer, _VSTD::end(_Buffer), _Value, _Effective_precision);
+        _LIBCPP_ASSERT(_Buf_result.ec == errc{}, "");
+        _Significand_last = _VSTD::find(_Buffer, _Buf_result.ptr, 'e');
+        _Exponent_first   = _Significand_last;
+        _Exponent_last    = _Buf_result.ptr;
+    }
+
+    // If we printed a decimal point followed by digits, perform zero-trimming.
+    if (_Effective_precision > 0) {
+        while (_Significand_last[-1] == '0') { // will stop at '.' or a nonzero digit
+            --_Significand_last;
+        }
+
+        if (_Significand_last[-1] == '.') {
+            --_Significand_last;
+        }
+    }
+
+    // Copy the significand to the output range.
+    const ptrdiff_t _Significand_distance = _Significand_last - _Significand_first;
+    if (_Last - _First < _Significand_distance) {
+        return {_Last, errc::value_too_large};
+    }
+    _VSTD::memcpy(_First, _Significand_first, static_cast<size_t>(_Significand_distance));
+    _First += _Significand_distance;
+
+    // Copy the exponent to the output range.
+    if (!_Use_fixed_notation) {
+        const ptrdiff_t _Exponent_distance = _Exponent_last - _Exponent_first;
+        if (_Last - _First < _Exponent_distance) {
+            return {_Last, errc::value_too_large};
+        }
+        _VSTD::memcpy(_First, _Exponent_first, static_cast<size_t>(_Exponent_distance));
+        _First += _Exponent_distance;
+    }
+
+    return {_First, errc{}};
+}
+
+enum class _Floating_to_chars_overload { _Plain, _Format_only, _Format_precision };
+
+template <_Floating_to_chars_overload _Overload, class _Floating>
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI
+to_chars_result _Floating_to_chars(
+    char* _First, char* const _Last, _Floating _Value, const chars_format _Fmt, const int _Precision) noexcept {
+
+    if constexpr (_Overload == _Floating_to_chars_overload::_Plain) {
+        _LIBCPP_ASSERT(_Fmt == chars_format{}, ""); // plain overload must pass chars_format{} internally
+    } else {
+        _LIBCPP_ASSERT(_Fmt == chars_format::general || _Fmt == chars_format::scientific || _Fmt == chars_format::fixed
+                         || _Fmt == chars_format::hex,
+            "invalid format in to_chars()");
+    }
+
+    using _Traits    = _Floating_type_traits<_Floating>;
+    using _Uint_type = typename _Traits::_Uint_type;
+
+    _Uint_type _Uint_value = _VSTD::bit_cast<_Uint_type>(_Value);
+
+    const bool _Was_negative = (_Uint_value & _Traits::_Shifted_sign_mask) != 0;
+
+    if (_Was_negative) { // sign bit detected; write minus sign and clear sign bit
+        if (_First == _Last) {
+            return {_Last, errc::value_too_large};
+        }
+
+        *_First++ = '-';
+
+        _Uint_value &= ~_Traits::_Shifted_sign_mask;
+        _Value = _VSTD::bit_cast<_Floating>(_Uint_value);
+    }
+
+    if ((_Uint_value & _Traits::_Shifted_exponent_mask) == _Traits::_Shifted_exponent_mask) {
+        // inf/nan detected; write appropriate string and return
+        const char* _Str;
+        size_t _Len;
+
+        const _Uint_type _Mantissa = _Uint_value & _Traits::_Denormal_mantissa_mask;
+
+        if (_Mantissa == 0) {
+            _Str = "inf";
+            _Len = 3;
+        } else if (_Was_negative && _Mantissa == _Traits::_Special_nan_mantissa_mask) {
+            // When a NaN value has the sign bit set, the quiet bit set, and all other mantissa bits cleared,
+            // the UCRT interprets it to mean "indeterminate", and indicates this by printing "-nan(ind)".
+            _Str = "nan(ind)";
+            _Len = 8;
+        } else if ((_Mantissa & _Traits::_Special_nan_mantissa_mask) != 0) {
+            _Str = "nan";
+            _Len = 3;
+        } else {
+            _Str = "nan(snan)";
+            _Len = 9;
+        }
+
+        if (_Last - _First < static_cast<ptrdiff_t>(_Len)) {
+            return {_Last, errc::value_too_large};
+        }
+
+        _VSTD::memcpy(_First, _Str, _Len);
+
+        return {_First + _Len, errc{}};
+    }
+
+    if constexpr (_Overload == _Floating_to_chars_overload::_Plain) {
+        return _Floating_to_chars_ryu(_First, _Last, _Value, chars_format{});
+    } else if constexpr (_Overload == _Floating_to_chars_overload::_Format_only) {
+        if (_Fmt == chars_format::hex) {
+            return _Floating_to_chars_hex_shortest(_First, _Last, _Value);
+        }
+
+        return _Floating_to_chars_ryu(_First, _Last, _Value, _Fmt);
+    } else if constexpr (_Overload == _Floating_to_chars_overload::_Format_precision) {
+        switch (_Fmt) {
+        case chars_format::scientific:
+            return _Floating_to_chars_scientific_precision(_First, _Last, _Value, _Precision);
+        case chars_format::fixed:
+            return _Floating_to_chars_fixed_precision(_First, _Last, _Value, _Precision);
+        case chars_format::general:
+            return _Floating_to_chars_general_precision(_First, _Last, _Value, _Precision);
+        case chars_format::hex:
+        default: // avoid MSVC warning C4715: not all control paths return a value
+            return _Floating_to_chars_hex_precision(_First, _Last, _Value, _Precision);
+        }
+    }
+}
+
+// clang-format on
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_SRC_INCLUDE_TO_CHARS_FLOATING_POINT_H

libcxx/src/ryu/README.txt

+The code in this directory is based on Ulf Adams's work. The upstream for the
+code is:
+
+https://github.com/ulfjack/ryu/tree/59661c3/ryu
+
+The code has been adapted by Stephan T. Lavavej of Microsoft for usage in
+std::to_chars. This code has been contributed by Microsoft for inclusion in
+libc++.
+
+The code in this directory has a different coding style than other parts to
+minimize the number of changes by both upstream sources.

libcxx/src/ryu/d2fixed.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+#include "charconv"
+#include "cstring"
+#include "system_error"
+
+#include "include/ryu/common.h"
+#include "include/ryu/d2fixed.h"
+#include "include/ryu/d2fixed_full_table.h"
+#include "include/ryu/d2s.h"
+#include "include/ryu/d2s_intrinsics.h"
+#include "include/ryu/digit_table.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline constexpr int __POW10_ADDITIONAL_BITS = 120;
+
+#ifdef _LIBCPP_INTRINSIC128
+// Returns the low 64 bits of the high 128 bits of the 256-bit product of a and b.
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __umul256_hi128_lo64(
+  const uint64_t __aHi, const uint64_t __aLo, const uint64_t __bHi, const uint64_t __bLo) {
+  uint64_t __b00Hi;
+  const uint64_t __b00Lo = __ryu_umul128(__aLo, __bLo, &__b00Hi);
+  uint64_t __b01Hi;
+  const uint64_t __b01Lo = __ryu_umul128(__aLo, __bHi, &__b01Hi);
+  uint64_t __b10Hi;
+  const uint64_t __b10Lo = __ryu_umul128(__aHi, __bLo, &__b10Hi);
+  uint64_t __b11Hi;
+  const uint64_t __b11Lo = __ryu_umul128(__aHi, __bHi, &__b11Hi);
+  (void) __b00Lo; // unused
+  (void) __b11Hi; // unused
+  const uint64_t __temp1Lo = __b10Lo + __b00Hi;
+  const uint64_t __temp1Hi = __b10Hi + (__temp1Lo < __b10Lo);
+  const uint64_t __temp2Lo = __b01Lo + __temp1Lo;
+  const uint64_t __temp2Hi = __b01Hi + (__temp2Lo < __b01Lo);
+  return __b11Lo + __temp1Hi + __temp2Hi;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __uint128_mod1e9(const uint64_t __vHi, const uint64_t __vLo) {
+  // After multiplying, we're going to shift right by 29, then truncate to uint32_t.
+  // This means that we need only 29 + 32 = 61 bits, so we can truncate to uint64_t before shifting.
+  const uint64_t __multiplied = __umul256_hi128_lo64(__vHi, __vLo, 0x89705F4136B4A597u, 0x31680A88F8953031u);
+
+  // For uint32_t truncation, see the __mod1e9() comment in d2s_intrinsics.h.
+  const uint32_t __shifted = static_cast<uint32_t>(__multiplied >> 29);
+
+  return static_cast<uint32_t>(__vLo) - 1000000000 * __shifted;
+}
+#endif // ^^^ intrinsics available ^^^
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mulShift_mod1e9(const uint64_t __m, const uint64_t* const __mul, const int32_t __j) {
+  uint64_t __high0;                                               // 64
+  const uint64_t __low0 = __ryu_umul128(__m, __mul[0], &__high0); // 0
+  uint64_t __high1;                                               // 128
+  const uint64_t __low1 = __ryu_umul128(__m, __mul[1], &__high1); // 64
+  uint64_t __high2;                                               // 192
+  const uint64_t __low2 = __ryu_umul128(__m, __mul[2], &__high2); // 128
+  const uint64_t __s0low = __low0;                  // 0
+  (void) __s0low; // unused
+  const uint64_t __s0high = __low1 + __high0;       // 64
+  const uint32_t __c1 = __s0high < __low1;
+  const uint64_t __s1low = __low2 + __high1 + __c1; // 128
+  const uint32_t __c2 = __s1low < __low2; // __high1 + __c1 can't overflow, so compare against __low2
+  const uint64_t __s1high = __high2 + __c2;         // 192
+  _LIBCPP_ASSERT(__j >= 128, "");
+  _LIBCPP_ASSERT(__j <= 180, "");
+#ifdef _LIBCPP_INTRINSIC128
+  const uint32_t __dist = static_cast<uint32_t>(__j - 128); // __dist: [0, 52]
+  const uint64_t __shiftedhigh = __s1high >> __dist;
+  const uint64_t __shiftedlow = __ryu_shiftright128(__s1low, __s1high, __dist);
+  return __uint128_mod1e9(__shiftedhigh, __shiftedlow);
+#else // ^^^ intrinsics available ^^^ / vvv intrinsics unavailable vvv
+  if (__j < 160) { // __j: [128, 160)
+    const uint64_t __r0 = __mod1e9(__s1high);
+    const uint64_t __r1 = __mod1e9((__r0 << 32) | (__s1low >> 32));
+    const uint64_t __r2 = ((__r1 << 32) | (__s1low & 0xffffffff));
+    return __mod1e9(__r2 >> (__j - 128));
+  } else { // __j: [160, 192)
+    const uint64_t __r0 = __mod1e9(__s1high);
+    const uint64_t __r1 = ((__r0 << 32) | (__s1low >> 32));
+    return __mod1e9(__r1 >> (__j - 160));
+  }
+#endif // ^^^ intrinsics unavailable ^^^
+}
+
+void __append_n_digits(const uint32_t __olength, uint32_t __digits, char* const __result) {
+  uint32_t __i = 0;
+  while (__digits >= 10000) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+    const uint32_t __c = __digits - 10000 * (__digits / 10000);
+#else
+    const uint32_t __c = __digits % 10000;
+#endif
+    __digits /= 10000;
+    const uint32_t __c0 = (__c % 100) << 1;
+    const uint32_t __c1 = (__c / 100) << 1;
+    _VSTD::memcpy(__result + __olength - __i - 2, __DIGIT_TABLE + __c0, 2);
+    _VSTD::memcpy(__result + __olength - __i - 4, __DIGIT_TABLE + __c1, 2);
+    __i += 4;
+  }
+  if (__digits >= 100) {
+    const uint32_t __c = (__digits % 100) << 1;
+    __digits /= 100;
+    _VSTD::memcpy(__result + __olength - __i - 2, __DIGIT_TABLE + __c, 2);
+    __i += 2;
+  }
+  if (__digits >= 10) {
+    const uint32_t __c = __digits << 1;
+    _VSTD::memcpy(__result + __olength - __i - 2, __DIGIT_TABLE + __c, 2);
+  } else {
+    __result[0] = static_cast<char>('0' + __digits);
+  }
+}
+
+_LIBCPP_HIDE_FROM_ABI inline void __append_d_digits(const uint32_t __olength, uint32_t __digits, char* const __result) {
+  uint32_t __i = 0;
+  while (__digits >= 10000) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+    const uint32_t __c = __digits - 10000 * (__digits / 10000);
+#else
+    const uint32_t __c = __digits % 10000;
+#endif
+    __digits /= 10000;
+    const uint32_t __c0 = (__c % 100) << 1;
+    const uint32_t __c1 = (__c / 100) << 1;
+    _VSTD::memcpy(__result + __olength + 1 - __i - 2, __DIGIT_TABLE + __c0, 2);
+    _VSTD::memcpy(__result + __olength + 1 - __i - 4, __DIGIT_TABLE + __c1, 2);
+    __i += 4;
+  }
+  if (__digits >= 100) {
+    const uint32_t __c = (__digits % 100) << 1;
+    __digits /= 100;
+    _VSTD::memcpy(__result + __olength + 1 - __i - 2, __DIGIT_TABLE + __c, 2);
+    __i += 2;
+  }
+  if (__digits >= 10) {
+    const uint32_t __c = __digits << 1;
+    __result[2] = __DIGIT_TABLE[__c + 1];
+    __result[1] = '.';
+    __result[0] = __DIGIT_TABLE[__c];
+  } else {
+    __result[1] = '.';
+    __result[0] = static_cast<char>('0' + __digits);
+  }
+}
+
+_LIBCPP_HIDE_FROM_ABI inline void __append_c_digits(const uint32_t __count, uint32_t __digits, char* const __result) {
+  uint32_t __i = 0;
+  for (; __i < __count - 1; __i += 2) {
+    const uint32_t __c = (__digits % 100) << 1;
+    __digits /= 100;
+    _VSTD::memcpy(__result + __count - __i - 2, __DIGIT_TABLE + __c, 2);
+  }
+  if (__i < __count) {
+    const char __c = static_cast<char>('0' + (__digits % 10));
+    __result[__count - __i - 1] = __c;
+  }
+}
+
+void __append_nine_digits(uint32_t __digits, char* const __result) {
+  if (__digits == 0) {
+    _VSTD::memset(__result, '0', 9);
+    return;
+  }
+
+  for (uint32_t __i = 0; __i < 5; __i += 4) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+    const uint32_t __c = __digits - 10000 * (__digits / 10000);
+#else
+    const uint32_t __c = __digits % 10000;
+#endif
+    __digits /= 10000;
+    const uint32_t __c0 = (__c % 100) << 1;
+    const uint32_t __c1 = (__c / 100) << 1;
+    _VSTD::memcpy(__result + 7 - __i, __DIGIT_TABLE + __c0, 2);
+    _VSTD::memcpy(__result + 5 - __i, __DIGIT_TABLE + __c1, 2);
+  }
+  __result[0] = static_cast<char>('0' + __digits);
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __indexForExponent(const uint32_t __e) {
+  return (__e + 15) / 16;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __pow10BitsForIndex(const uint32_t __idx) {
+  return 16 * __idx + __POW10_ADDITIONAL_BITS;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __lengthForIndex(const uint32_t __idx) {
+  // +1 for ceil, +16 for mantissa, +8 to round up when dividing by 9
+  return (__log10Pow2(16 * static_cast<int32_t>(__idx)) + 1 + 16 + 8) / 9;
+}
+
+[[nodiscard]] to_chars_result __d2fixed_buffered_n(char* _First, char* const _Last, const double __d,
+  const uint32_t __precision) {
+  char* const _Original_first = _First;
+
+  const uint64_t __bits = __double_to_bits(__d);
+
+  // Case distinction; exit early for the easy cases.
+  if (__bits == 0) {
+    const int32_t _Total_zero_length = 1 // leading zero
+      + static_cast<int32_t>(__precision != 0) // possible decimal point
+      + static_cast<int32_t>(__precision); // zeroes after decimal point
+
+    if (_Last - _First < _Total_zero_length) {
+      return { _Last, errc::value_too_large };
+    }
+
+    *_First++ = '0';
+    if (__precision > 0) {
+      *_First++ = '.';
+      _VSTD::memset(_First, '0', __precision);
+      _First += __precision;
+    }
+    return { _First, errc{} };
+  }
+
+  // Decode __bits into mantissa and exponent.
+  const uint64_t __ieeeMantissa = __bits & ((1ull << __DOUBLE_MANTISSA_BITS) - 1);
+  const uint32_t __ieeeExponent = static_cast<uint32_t>(__bits >> __DOUBLE_MANTISSA_BITS);
+
+  int32_t __e2;
+  uint64_t __m2;
+  if (__ieeeExponent == 0) {
+    __e2 = 1 - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS;
+    __m2 = __ieeeMantissa;
+  } else {
+    __e2 = static_cast<int32_t>(__ieeeExponent) - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS;
+    __m2 = (1ull << __DOUBLE_MANTISSA_BITS) | __ieeeMantissa;
+  }
+
+  bool __nonzero = false;
+  if (__e2 >= -52) {
+    const uint32_t __idx = __e2 < 0 ? 0 : __indexForExponent(static_cast<uint32_t>(__e2));
+    const uint32_t __p10bits = __pow10BitsForIndex(__idx);
+    const int32_t __len = static_cast<int32_t>(__lengthForIndex(__idx));
+    for (int32_t __i = __len - 1; __i >= 0; --__i) {
+      const uint32_t __j = __p10bits - __e2;
+      // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is
+      // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers.
+      const uint32_t __digits = __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT[__POW10_OFFSET[__idx] + __i],
+        static_cast<int32_t>(__j + 8));
+      if (__nonzero) {
+        if (_Last - _First < 9) {
+          return { _Last, errc::value_too_large };
+        }
+        __append_nine_digits(__digits, _First);
+        _First += 9;
+      } else if (__digits != 0) {
+        const uint32_t __olength = __decimalLength9(__digits);
+        if (_Last - _First < static_cast<ptrdiff_t>(__olength)) {
+          return { _Last, errc::value_too_large };
+        }
+        __append_n_digits(__olength, __digits, _First);
+        _First += __olength;
+        __nonzero = true;
+      }
+    }
+  }
+  if (!__nonzero) {
+    if (_First == _Last) {
+      return { _Last, errc::value_too_large };
+    }
+    *_First++ = '0';
+  }
+  if (__precision > 0) {
+    if (_First == _Last) {
+      return { _Last, errc::value_too_large };
+    }
+    *_First++ = '.';
+  }
+  if (__e2 < 0) {
+    const int32_t __idx = -__e2 / 16;
+    const uint32_t __blocks = __precision / 9 + 1;
+    // 0 = don't round up; 1 = round up unconditionally; 2 = round up if odd.
+    int __roundUp = 0;
+    uint32_t __i = 0;
+    if (__blocks <= __MIN_BLOCK_2[__idx]) {
+      __i = __blocks;
+      if (_Last - _First < static_cast<ptrdiff_t>(__precision)) {
+        return { _Last, errc::value_too_large };
+      }
+      _VSTD::memset(_First, '0', __precision);
+      _First += __precision;
+    } else if (__i < __MIN_BLOCK_2[__idx]) {
+      __i = __MIN_BLOCK_2[__idx];
+      if (_Last - _First < static_cast<ptrdiff_t>(9 * __i)) {
+        return { _Last, errc::value_too_large };
+      }
+      _VSTD::memset(_First, '0', 9 * __i);
+      _First += 9 * __i;
+    }
+    for (; __i < __blocks; ++__i) {
+      const int32_t __j = __ADDITIONAL_BITS_2 + (-__e2 - 16 * __idx);
+      const uint32_t __p = __POW10_OFFSET_2[__idx] + __i - __MIN_BLOCK_2[__idx];
+      if (__p >= __POW10_OFFSET_2[__idx + 1]) {
+        // If the remaining digits are all 0, then we might as well use memset.
+        // No rounding required in this case.
+        const uint32_t __fill = __precision - 9 * __i;
+        if (_Last - _First < static_cast<ptrdiff_t>(__fill)) {
+          return { _Last, errc::value_too_large };
+        }
+        _VSTD::memset(_First, '0', __fill);
+        _First += __fill;
+        break;
+      }
+      // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is
+      // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers.
+      uint32_t __digits = __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT_2[__p], __j + 8);
+      if (__i < __blocks - 1) {
+        if (_Last - _First < 9) {
+          return { _Last, errc::value_too_large };
+        }
+        __append_nine_digits(__digits, _First);
+        _First += 9;
+      } else {
+        const uint32_t __maximum = __precision - 9 * __i;
+        uint32_t __lastDigit = 0;
+        for (uint32_t __k = 0; __k < 9 - __maximum; ++__k) {
+          __lastDigit = __digits % 10;
+          __digits /= 10;
+        }
+        if (__lastDigit != 5) {
+          __roundUp = __lastDigit > 5;
+        } else {
+          // Is m * 10^(additionalDigits + 1) / 2^(-__e2) integer?
+          const int32_t __requiredTwos = -__e2 - static_cast<int32_t>(__precision) - 1;
+          const bool __trailingZeros = __requiredTwos <= 0
+            || (__requiredTwos < 60 && __multipleOfPowerOf2(__m2, static_cast<uint32_t>(__requiredTwos)));
+          __roundUp = __trailingZeros ? 2 : 1;
+        }
+        if (__maximum > 0) {
+          if (_Last - _First < static_cast<ptrdiff_t>(__maximum)) {
+            return { _Last, errc::value_too_large };
+          }
+          __append_c_digits(__maximum, __digits, _First);
+          _First += __maximum;
+        }
+        break;
+      }
+    }
+    if (__roundUp != 0) {
+      char* _Round = _First;
+      char* _Dot = _Last;
+      while (true) {
+        if (_Round == _Original_first) {
+          _Round[0] = '1';
+          if (_Dot != _Last) {
+            _Dot[0] = '0';
+            _Dot[1] = '.';
+          }
+          if (_First == _Last) {
+            return { _Last, errc::value_too_large };
+          }
+          *_First++ = '0';
+          break;
+        }
+        --_Round;
+        const char __c = _Round[0];
+        if (__c == '.') {
+          _Dot = _Round;
+        } else if (__c == '9') {
+          _Round[0] = '0';
+          __roundUp = 1;
+        } else {
+          if (__roundUp == 1 || __c % 2 != 0) {
+            _Round[0] = __c + 1;
+          }
+          break;
+        }
+      }
+    }
+  } else {
+    if (_Last - _First < static_cast<ptrdiff_t>(__precision)) {
+      return { _Last, errc::value_too_large };
+    }
+    _VSTD::memset(_First, '0', __precision);
+    _First += __precision;
+  }
+  return { _First, errc{} };
+}
+
+[[nodiscard]] to_chars_result __d2exp_buffered_n(char* _First, char* const _Last, const double __d,
+  uint32_t __precision) {
+  char* const _Original_first = _First;
+
+  const uint64_t __bits = __double_to_bits(__d);
+
+  // Case distinction; exit early for the easy cases.
+  if (__bits == 0) {
+    const int32_t _Total_zero_length = 1 // leading zero
+      + static_cast<int32_t>(__precision != 0) // possible decimal point
+      + static_cast<int32_t>(__precision) // zeroes after decimal point
+      + 4; // "e+00"
+    if (_Last - _First < _Total_zero_length) {
+      return { _Last, errc::value_too_large };
+    }
+    *_First++ = '0';
+    if (__precision > 0) {
+      *_First++ = '.';
+      _VSTD::memset(_First, '0', __precision);
+      _First += __precision;
+    }
+    _VSTD::memcpy(_First, "e+00", 4);
+    _First += 4;
+    return { _First, errc{} };
+  }
+
+  // Decode __bits into mantissa and exponent.
+  const uint64_t __ieeeMantissa = __bits & ((1ull << __DOUBLE_MANTISSA_BITS) - 1);
+  const uint32_t __ieeeExponent = static_cast<uint32_t>(__bits >> __DOUBLE_MANTISSA_BITS);
+
+  int32_t __e2;
+  uint64_t __m2;
+  if (__ieeeExponent == 0) {
+    __e2 = 1 - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS;
+    __m2 = __ieeeMantissa;
+  } else {
+    __e2 = static_cast<int32_t>(__ieeeExponent) - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS;
+    __m2 = (1ull << __DOUBLE_MANTISSA_BITS) | __ieeeMantissa;
+  }
+
+  const bool __printDecimalPoint = __precision > 0;
+  ++__precision;
+  uint32_t __digits = 0;
+  uint32_t __printedDigits = 0;
+  uint32_t __availableDigits = 0;
+  int32_t __exp = 0;
+  if (__e2 >= -52) {
+    const uint32_t __idx = __e2 < 0 ? 0 : __indexForExponent(static_cast<uint32_t>(__e2));
+    const uint32_t __p10bits = __pow10BitsForIndex(__idx);
+    const int32_t __len = static_cast<int32_t>(__lengthForIndex(__idx));
+    for (int32_t __i = __len - 1; __i >= 0; --__i) {
+      const uint32_t __j = __p10bits - __e2;
+      // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is
+      // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers.
+      __digits = __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT[__POW10_OFFSET[__idx] + __i],
+        static_cast<int32_t>(__j + 8));
+      if (__printedDigits != 0) {
+        if (__printedDigits + 9 > __precision) {
+          __availableDigits = 9;
+          break;
+        }
+        if (_Last - _First < 9) {
+          return { _Last, errc::value_too_large };
+        }
+        __append_nine_digits(__digits, _First);
+        _First += 9;
+        __printedDigits += 9;
+      } else if (__digits != 0) {
+        __availableDigits = __decimalLength9(__digits);
+        __exp = __i * 9 + static_cast<int32_t>(__availableDigits) - 1;
+        if (__availableDigits > __precision) {
+          break;
+        }
+        if (__printDecimalPoint) {
+          if (_Last - _First < static_cast<ptrdiff_t>(__availableDigits + 1)) {
+            return { _Last, errc::value_too_large };
+          }
+          __append_d_digits(__availableDigits, __digits, _First);
+          _First += __availableDigits + 1; // +1 for decimal point
+        } else {
+          if (_First == _Last) {
+            return { _Last, errc::value_too_large };
+          }
+          *_First++ = static_cast<char>('0' + __digits);
+        }
+        __printedDigits = __availableDigits;
+        __availableDigits = 0;
+      }
+    }
+  }
+
+  if (__e2 < 0 && __availableDigits == 0) {
+    const int32_t __idx = -__e2 / 16;
+    for (int32_t __i = __MIN_BLOCK_2[__idx]; __i < 200; ++__i) {
+      const int32_t __j = __ADDITIONAL_BITS_2 + (-__e2 - 16 * __idx);
+      const uint32_t __p = __POW10_OFFSET_2[__idx] + static_cast<uint32_t>(__i) - __MIN_BLOCK_2[__idx];
+      // Temporary: __j is usually around 128, and by shifting a bit, we push it to 128 or above, which is
+      // a slightly faster code path in __mulShift_mod1e9. Instead, we can just increase the multipliers.
+      __digits = (__p >= __POW10_OFFSET_2[__idx + 1]) ? 0 : __mulShift_mod1e9(__m2 << 8, __POW10_SPLIT_2[__p], __j + 8);
+      if (__printedDigits != 0) {
+        if (__printedDigits + 9 > __precision) {
+          __availableDigits = 9;
+          break;
+        }
+        if (_Last - _First < 9) {
+          return { _Last, errc::value_too_large };
+        }
+        __append_nine_digits(__digits, _First);
+        _First += 9;
+        __printedDigits += 9;
+      } else if (__digits != 0) {
+        __availableDigits = __decimalLength9(__digits);
+        __exp = -(__i + 1) * 9 + static_cast<int32_t>(__availableDigits) - 1;
+        if (__availableDigits > __precision) {
+          break;
+        }
+        if (__printDecimalPoint) {
+          if (_Last - _First < static_cast<ptrdiff_t>(__availableDigits + 1)) {
+            return { _Last, errc::value_too_large };
+          }
+          __append_d_digits(__availableDigits, __digits, _First);
+          _First += __availableDigits + 1; // +1 for decimal point
+        } else {
+          if (_First == _Last) {
+            return { _Last, errc::value_too_large };
+          }
+          *_First++ = static_cast<char>('0' + __digits);
+        }
+        __printedDigits = __availableDigits;
+        __availableDigits = 0;
+      }
+    }
+  }
+
+  const uint32_t __maximum = __precision - __printedDigits;
+  if (__availableDigits == 0) {
+    __digits = 0;
+  }
+  uint32_t __lastDigit = 0;
+  if (__availableDigits > __maximum) {
+    for (uint32_t __k = 0; __k < __availableDigits - __maximum; ++__k) {
+      __lastDigit = __digits % 10;
+      __digits /= 10;
+    }
+  }
+  // 0 = don't round up; 1 = round up unconditionally; 2 = round up if odd.
+  int __roundUp = 0;
+  if (__lastDigit != 5) {
+    __roundUp = __lastDigit > 5;
+  } else {
+    // Is m * 2^__e2 * 10^(__precision + 1 - __exp) integer?
+    // __precision was already increased by 1, so we don't need to write + 1 here.
+    const int32_t __rexp = static_cast<int32_t>(__precision) - __exp;
+    const int32_t __requiredTwos = -__e2 - __rexp;
+    bool __trailingZeros = __requiredTwos <= 0
+      || (__requiredTwos < 60 && __multipleOfPowerOf2(__m2, static_cast<uint32_t>(__requiredTwos)));
+    if (__rexp < 0) {
+      const int32_t __requiredFives = -__rexp;
+      __trailingZeros = __trailingZeros && __multipleOfPowerOf5(__m2, static_cast<uint32_t>(__requiredFives));
+    }
+    __roundUp = __trailingZeros ? 2 : 1;
+  }
+  if (__printedDigits != 0) {
+    if (_Last - _First < static_cast<ptrdiff_t>(__maximum)) {
+      return { _Last, errc::value_too_large };
+    }
+    if (__digits == 0) {
+      _VSTD::memset(_First, '0', __maximum);
+    } else {
+      __append_c_digits(__maximum, __digits, _First);
+    }
+    _First += __maximum;
+  } else {
+    if (__printDecimalPoint) {
+      if (_Last - _First < static_cast<ptrdiff_t>(__maximum + 1)) {
+        return { _Last, errc::value_too_large };
+      }
+      __append_d_digits(__maximum, __digits, _First);
+      _First += __maximum + 1; // +1 for decimal point
+    } else {
+      if (_First == _Last) {
+        return { _Last, errc::value_too_large };
+      }
+      *_First++ = static_cast<char>('0' + __digits);
+    }
+  }
+  if (__roundUp != 0) {
+    char* _Round = _First;
+    while (true) {
+      if (_Round == _Original_first) {
+        _Round[0] = '1';
+        ++__exp;
+        break;
+      }
+      --_Round;
+      const char __c = _Round[0];
+      if (__c == '.') {
+        // Keep going.
+      } else if (__c == '9') {
+        _Round[0] = '0';
+        __roundUp = 1;
+      } else {
+        if (__roundUp == 1 || __c % 2 != 0) {
+          _Round[0] = __c + 1;
+        }
+        break;
+      }
+    }
+  }
+
+  char _Sign_character;
+
+  if (__exp < 0) {
+    _Sign_character = '-';
+    __exp = -__exp;
+  } else {
+    _Sign_character = '+';
+  }
+
+  const int _Exponent_part_length = __exp >= 100
+    ? 5 // "e+NNN"
+    : 4; // "e+NN"
+
+  if (_Last - _First < _Exponent_part_length) {
+    return { _Last, errc::value_too_large };
+  }
+
+  *_First++ = 'e';
+  *_First++ = _Sign_character;
+
+  if (__exp >= 100) {
+    const int32_t __c = __exp % 10;
+    _VSTD::memcpy(_First, __DIGIT_TABLE + 2 * (__exp / 10), 2);
+    _First[2] = static_cast<char>('0' + __c);
+    _First += 3;
+  } else {
+    _VSTD::memcpy(_First, __DIGIT_TABLE + 2 * __exp, 2);
+    _First += 2;
+  }
+
+  return { _First, errc{} };
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on

libcxx/src/ryu/d2s.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+#include "charconv"
+
+#include "include/ryu/common.h"
+#include "include/ryu/d2fixed.h"
+#include "include/ryu/d2s.h"
+#include "include/ryu/d2s_full_table.h"
+#include "include/ryu/d2s_intrinsics.h"
+#include "include/ryu/digit_table.h"
+#include "include/ryu/ryu.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+// We need a 64x128-bit multiplication and a subsequent 128-bit shift.
+// Multiplication:
+//   The 64-bit factor is variable and passed in, the 128-bit factor comes
+//   from a lookup table. We know that the 64-bit factor only has 55
+//   significant bits (i.e., the 9 topmost bits are zeros). The 128-bit
+//   factor only has 124 significant bits (i.e., the 4 topmost bits are
+//   zeros).
+// Shift:
+//   In principle, the multiplication result requires 55 + 124 = 179 bits to
+//   represent. However, we then shift this value to the right by __j, which is
+//   at least __j >= 115, so the result is guaranteed to fit into 179 - 115 = 64
+//   bits. This means that we only need the topmost 64 significant bits of
+//   the 64x128-bit multiplication.
+//
+// There are several ways to do this:
+// 1. Best case: the compiler exposes a 128-bit type.
+//    We perform two 64x64-bit multiplications, add the higher 64 bits of the
+//    lower result to the higher result, and shift by __j - 64 bits.
+//
+//    We explicitly cast from 64-bit to 128-bit, so the compiler can tell
+//    that these are only 64-bit inputs, and can map these to the best
+//    possible sequence of assembly instructions.
+//    x64 machines happen to have matching assembly instructions for
+//    64x64-bit multiplications and 128-bit shifts.
+//
+// 2. Second best case: the compiler exposes intrinsics for the x64 assembly
+//    instructions mentioned in 1.
+//
+// 3. We only have 64x64 bit instructions that return the lower 64 bits of
+//    the result, i.e., we have to use plain C.
+//    Our inputs are less than the full width, so we have three options:
+//    a. Ignore this fact and just implement the intrinsics manually.
+//    b. Split both into 31-bit pieces, which guarantees no internal overflow,
+//       but requires extra work upfront (unless we change the lookup table).
+//    c. Split only the first factor into 31-bit pieces, which also guarantees
+//       no internal overflow, but requires extra work since the intermediate
+//       results are not perfectly aligned.
+#ifdef _LIBCPP_INTRINSIC128
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __mulShift(const uint64_t __m, const uint64_t* const __mul, const int32_t __j) {
+  // __m is maximum 55 bits
+  uint64_t __high1;                                               // 128
+  const uint64_t __low1 = __ryu_umul128(__m, __mul[1], &__high1); // 64
+  uint64_t __high0;                                               // 64
+  (void) __ryu_umul128(__m, __mul[0], &__high0);                  // 0
+  const uint64_t __sum = __high0 + __low1;
+  if (__sum < __high0) {
+    ++__high1; // overflow into __high1
+  }
+  return __ryu_shiftright128(__sum, __high1, static_cast<uint32_t>(__j - 64));
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint64_t __mulShiftAll(const uint64_t __m, const uint64_t* const __mul, const int32_t __j,
+  uint64_t* const __vp, uint64_t* const __vm, const uint32_t __mmShift) {
+  *__vp = __mulShift(4 * __m + 2, __mul, __j);
+  *__vm = __mulShift(4 * __m - 1 - __mmShift, __mul, __j);
+  return __mulShift(4 * __m, __mul, __j);
+}
+
+#else // ^^^ intrinsics available ^^^ / vvv intrinsics unavailable vvv
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline _LIBCPP_ALWAYS_INLINE uint64_t __mulShiftAll(uint64_t __m, const uint64_t* const __mul, const int32_t __j,
+  uint64_t* const __vp, uint64_t* const __vm, const uint32_t __mmShift) { // TRANSITION, VSO-634761
+  __m <<= 1;
+  // __m is maximum 55 bits
+  uint64_t __tmp;
+  const uint64_t __lo = __ryu_umul128(__m, __mul[0], &__tmp);
+  uint64_t __hi;
+  const uint64_t __mid = __tmp + __ryu_umul128(__m, __mul[1], &__hi);
+  __hi += __mid < __tmp; // overflow into __hi
+
+  const uint64_t __lo2 = __lo + __mul[0];
+  const uint64_t __mid2 = __mid + __mul[1] + (__lo2 < __lo);
+  const uint64_t __hi2 = __hi + (__mid2 < __mid);
+  *__vp = __ryu_shiftright128(__mid2, __hi2, static_cast<uint32_t>(__j - 64 - 1));
+
+  if (__mmShift == 1) {
+    const uint64_t __lo3 = __lo - __mul[0];
+    const uint64_t __mid3 = __mid - __mul[1] - (__lo3 > __lo);
+    const uint64_t __hi3 = __hi - (__mid3 > __mid);
+    *__vm = __ryu_shiftright128(__mid3, __hi3, static_cast<uint32_t>(__j - 64 - 1));
+  } else {
+    const uint64_t __lo3 = __lo + __lo;
+    const uint64_t __mid3 = __mid + __mid + (__lo3 < __lo);
+    const uint64_t __hi3 = __hi + __hi + (__mid3 < __mid);
+    const uint64_t __lo4 = __lo3 - __mul[0];
+    const uint64_t __mid4 = __mid3 - __mul[1] - (__lo4 > __lo3);
+    const uint64_t __hi4 = __hi3 - (__mid4 > __mid3);
+    *__vm = __ryu_shiftright128(__mid4, __hi4, static_cast<uint32_t>(__j - 64));
+  }
+
+  return __ryu_shiftright128(__mid, __hi, static_cast<uint32_t>(__j - 64 - 1));
+}
+
+#endif // ^^^ intrinsics unavailable ^^^
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __decimalLength17(const uint64_t __v) {
+  // This is slightly faster than a loop.
+  // The average output length is 16.38 digits, so we check high-to-low.
+  // Function precondition: __v is not an 18, 19, or 20-digit number.
+  // (17 digits are sufficient for round-tripping.)
+  _LIBCPP_ASSERT(__v < 100000000000000000u, "");
+  if (__v >= 10000000000000000u) { return 17; }
+  if (__v >= 1000000000000000u) { return 16; }
+  if (__v >= 100000000000000u) { return 15; }
+  if (__v >= 10000000000000u) { return 14; }
+  if (__v >= 1000000000000u) { return 13; }
+  if (__v >= 100000000000u) { return 12; }
+  if (__v >= 10000000000u) { return 11; }
+  if (__v >= 1000000000u) { return 10; }
+  if (__v >= 100000000u) { return 9; }
+  if (__v >= 10000000u) { return 8; }
+  if (__v >= 1000000u) { return 7; }
+  if (__v >= 100000u) { return 6; }
+  if (__v >= 10000u) { return 5; }
+  if (__v >= 1000u) { return 4; }
+  if (__v >= 100u) { return 3; }
+  if (__v >= 10u) { return 2; }
+  return 1;
+}
+
+// A floating decimal representing m * 10^e.
+struct __floating_decimal_64 {
+  uint64_t __mantissa;
+  int32_t __exponent;
+};
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline __floating_decimal_64 __d2d(const uint64_t __ieeeMantissa, const uint32_t __ieeeExponent) {
+  int32_t __e2;
+  uint64_t __m2;
+  if (__ieeeExponent == 0) {
+    // We subtract 2 so that the bounds computation has 2 additional bits.
+    __e2 = 1 - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS - 2;
+    __m2 = __ieeeMantissa;
+  } else {
+    __e2 = static_cast<int32_t>(__ieeeExponent) - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS - 2;
+    __m2 = (1ull << __DOUBLE_MANTISSA_BITS) | __ieeeMantissa;
+  }
+  const bool __even = (__m2 & 1) == 0;
+  const bool __acceptBounds = __even;
+
+  // Step 2: Determine the interval of valid decimal representations.
+  const uint64_t __mv = 4 * __m2;
+  // Implicit bool -> int conversion. True is 1, false is 0.
+  const uint32_t __mmShift = __ieeeMantissa != 0 || __ieeeExponent <= 1;
+  // We would compute __mp and __mm like this:
+  // uint64_t __mp = 4 * __m2 + 2;
+  // uint64_t __mm = __mv - 1 - __mmShift;
+
+  // Step 3: Convert to a decimal power base using 128-bit arithmetic.
+  uint64_t __vr, __vp, __vm;
+  int32_t __e10;
+  bool __vmIsTrailingZeros = false;
+  bool __vrIsTrailingZeros = false;
+  if (__e2 >= 0) {
+    // I tried special-casing __q == 0, but there was no effect on performance.
+    // This expression is slightly faster than max(0, __log10Pow2(__e2) - 1).
+    const uint32_t __q = __log10Pow2(__e2) - (__e2 > 3);
+    __e10 = static_cast<int32_t>(__q);
+    const int32_t __k = __DOUBLE_POW5_INV_BITCOUNT + __pow5bits(static_cast<int32_t>(__q)) - 1;
+    const int32_t __i = -__e2 + static_cast<int32_t>(__q) + __k;
+    __vr = __mulShiftAll(__m2, __DOUBLE_POW5_INV_SPLIT[__q], __i, &__vp, &__vm, __mmShift);
+    if (__q <= 21) {
+      // This should use __q <= 22, but I think 21 is also safe. Smaller values
+      // may still be safe, but it's more difficult to reason about them.
+      // Only one of __mp, __mv, and __mm can be a multiple of 5, if any.
+      const uint32_t __mvMod5 = static_cast<uint32_t>(__mv) - 5 * static_cast<uint32_t>(__div5(__mv));
+      if (__mvMod5 == 0) {
+        __vrIsTrailingZeros = __multipleOfPowerOf5(__mv, __q);
+      } else if (__acceptBounds) {
+        // Same as min(__e2 + (~__mm & 1), __pow5Factor(__mm)) >= __q
+        // <=> __e2 + (~__mm & 1) >= __q && __pow5Factor(__mm) >= __q
+        // <=> true && __pow5Factor(__mm) >= __q, since __e2 >= __q.
+        __vmIsTrailingZeros = __multipleOfPowerOf5(__mv - 1 - __mmShift, __q);
+      } else {
+        // Same as min(__e2 + 1, __pow5Factor(__mp)) >= __q.
+        __vp -= __multipleOfPowerOf5(__mv + 2, __q);
+      }
+    }
+  } else {
+    // This expression is slightly faster than max(0, __log10Pow5(-__e2) - 1).
+    const uint32_t __q = __log10Pow5(-__e2) - (-__e2 > 1);
+    __e10 = static_cast<int32_t>(__q) + __e2;
+    const int32_t __i = -__e2 - static_cast<int32_t>(__q);
+    const int32_t __k = __pow5bits(__i) - __DOUBLE_POW5_BITCOUNT;
+    const int32_t __j = static_cast<int32_t>(__q) - __k;
+    __vr = __mulShiftAll(__m2, __DOUBLE_POW5_SPLIT[__i], __j, &__vp, &__vm, __mmShift);
+    if (__q <= 1) {
+      // {__vr,__vp,__vm} is trailing zeros if {__mv,__mp,__mm} has at least __q trailing 0 bits.
+      // __mv = 4 * __m2, so it always has at least two trailing 0 bits.
+      __vrIsTrailingZeros = true;
+      if (__acceptBounds) {
+        // __mm = __mv - 1 - __mmShift, so it has 1 trailing 0 bit iff __mmShift == 1.
+        __vmIsTrailingZeros = __mmShift == 1;
+      } else {
+        // __mp = __mv + 2, so it always has at least one trailing 0 bit.
+        --__vp;
+      }
+    } else if (__q < 63) { // TRANSITION(ulfjack): Use a tighter bound here.
+      // We need to compute min(ntz(__mv), __pow5Factor(__mv) - __e2) >= __q - 1
+      // <=> ntz(__mv) >= __q - 1 && __pow5Factor(__mv) - __e2 >= __q - 1
+      // <=> ntz(__mv) >= __q - 1 (__e2 is negative and -__e2 >= __q)
+      // <=> (__mv & ((1 << (__q - 1)) - 1)) == 0
+      // We also need to make sure that the left shift does not overflow.
+      __vrIsTrailingZeros = __multipleOfPowerOf2(__mv, __q - 1);
+    }
+  }
+
+  // Step 4: Find the shortest decimal representation in the interval of valid representations.
+  int32_t __removed = 0;
+  uint8_t __lastRemovedDigit = 0;
+  uint64_t _Output;
+  // On average, we remove ~2 digits.
+  if (__vmIsTrailingZeros || __vrIsTrailingZeros) {
+    // General case, which happens rarely (~0.7%).
+    for (;;) {
+      const uint64_t __vpDiv10 = __div10(__vp);
+      const uint64_t __vmDiv10 = __div10(__vm);
+      if (__vpDiv10 <= __vmDiv10) {
+        break;
+      }
+      const uint32_t __vmMod10 = static_cast<uint32_t>(__vm) - 10 * static_cast<uint32_t>(__vmDiv10);
+      const uint64_t __vrDiv10 = __div10(__vr);
+      const uint32_t __vrMod10 = static_cast<uint32_t>(__vr) - 10 * static_cast<uint32_t>(__vrDiv10);
+      __vmIsTrailingZeros &= __vmMod10 == 0;
+      __vrIsTrailingZeros &= __lastRemovedDigit == 0;
+      __lastRemovedDigit = static_cast<uint8_t>(__vrMod10);
+      __vr = __vrDiv10;
+      __vp = __vpDiv10;
+      __vm = __vmDiv10;
+      ++__removed;
+    }
+    if (__vmIsTrailingZeros) {
+      for (;;) {
+        const uint64_t __vmDiv10 = __div10(__vm);
+        const uint32_t __vmMod10 = static_cast<uint32_t>(__vm) - 10 * static_cast<uint32_t>(__vmDiv10);
+        if (__vmMod10 != 0) {
+          break;
+        }
+        const uint64_t __vpDiv10 = __div10(__vp);
+        const uint64_t __vrDiv10 = __div10(__vr);
+        const uint32_t __vrMod10 = static_cast<uint32_t>(__vr) - 10 * static_cast<uint32_t>(__vrDiv10);
+        __vrIsTrailingZeros &= __lastRemovedDigit == 0;
+        __lastRemovedDigit = static_cast<uint8_t>(__vrMod10);
+        __vr = __vrDiv10;
+        __vp = __vpDiv10;
+        __vm = __vmDiv10;
+        ++__removed;
+      }
+    }
+    if (__vrIsTrailingZeros && __lastRemovedDigit == 5 && __vr % 2 == 0) {
+      // Round even if the exact number is .....50..0.
+      __lastRemovedDigit = 4;
+    }
+    // We need to take __vr + 1 if __vr is outside bounds or we need to round up.
+    _Output = __vr + ((__vr == __vm && (!__acceptBounds || !__vmIsTrailingZeros)) || __lastRemovedDigit >= 5);
+  } else {
+    // Specialized for the common case (~99.3%). Percentages below are relative to this.
+    bool __roundUp = false;
+    const uint64_t __vpDiv100 = __div100(__vp);
+    const uint64_t __vmDiv100 = __div100(__vm);
+    if (__vpDiv100 > __vmDiv100) { // Optimization: remove two digits at a time (~86.2%).
+      const uint64_t __vrDiv100 = __div100(__vr);
+      const uint32_t __vrMod100 = static_cast<uint32_t>(__vr) - 100 * static_cast<uint32_t>(__vrDiv100);
+      __roundUp = __vrMod100 >= 50;
+      __vr = __vrDiv100;
+      __vp = __vpDiv100;
+      __vm = __vmDiv100;
+      __removed += 2;
+    }
+    // Loop iterations below (approximately), without optimization above:
+    // 0: 0.03%, 1: 13.8%, 2: 70.6%, 3: 14.0%, 4: 1.40%, 5: 0.14%, 6+: 0.02%
+    // Loop iterations below (approximately), with optimization above:
+    // 0: 70.6%, 1: 27.8%, 2: 1.40%, 3: 0.14%, 4+: 0.02%
+    for (;;) {
+      const uint64_t __vpDiv10 = __div10(__vp);
+      const uint64_t __vmDiv10 = __div10(__vm);
+      if (__vpDiv10 <= __vmDiv10) {
+        break;
+      }
+      const uint64_t __vrDiv10 = __div10(__vr);
+      const uint32_t __vrMod10 = static_cast<uint32_t>(__vr) - 10 * static_cast<uint32_t>(__vrDiv10);
+      __roundUp = __vrMod10 >= 5;
+      __vr = __vrDiv10;
+      __vp = __vpDiv10;
+      __vm = __vmDiv10;
+      ++__removed;
+    }
+    // We need to take __vr + 1 if __vr is outside bounds or we need to round up.
+    _Output = __vr + (__vr == __vm || __roundUp);
+  }
+  const int32_t __exp = __e10 + __removed;
+
+  __floating_decimal_64 __fd;
+  __fd.__exponent = __exp;
+  __fd.__mantissa = _Output;
+  return __fd;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline to_chars_result __to_chars(char* const _First, char* const _Last, const __floating_decimal_64 __v,
+  chars_format _Fmt, const double __f) {
+  // Step 5: Print the decimal representation.
+  uint64_t _Output = __v.__mantissa;
+  int32_t _Ryu_exponent = __v.__exponent;
+  const uint32_t __olength = __decimalLength17(_Output);
+  int32_t _Scientific_exponent = _Ryu_exponent + static_cast<int32_t>(__olength) - 1;
+
+  if (_Fmt == chars_format{}) {
+    int32_t _Lower;
+    int32_t _Upper;
+
+    if (__olength == 1) {
+      // Value | Fixed   | Scientific
+      // 1e-3  | "0.001" | "1e-03"
+      // 1e4   | "10000" | "1e+04"
+      _Lower = -3;
+      _Upper = 4;
+    } else {
+      // Value   | Fixed       | Scientific
+      // 1234e-7 | "0.0001234" | "1.234e-04"
+      // 1234e5  | "123400000" | "1.234e+08"
+      _Lower = -static_cast<int32_t>(__olength + 3);
+      _Upper = 5;
+    }
+
+    if (_Lower <= _Ryu_exponent && _Ryu_exponent <= _Upper) {
+      _Fmt = chars_format::fixed;
+    } else {
+      _Fmt = chars_format::scientific;
+    }
+  } else if (_Fmt == chars_format::general) {
+    // C11 7.21.6.1 "The fprintf function"/8:
+    // "Let P equal [...] 6 if the precision is omitted [...].
+    // Then, if a conversion with style E would have an exponent of X:
+    // - if P > X >= -4, the conversion is with style f [...].
+    // - otherwise, the conversion is with style e [...]."
+    if (-4 <= _Scientific_exponent && _Scientific_exponent < 6) {
+      _Fmt = chars_format::fixed;
+    } else {
+      _Fmt = chars_format::scientific;
+    }
+  }
+
+  if (_Fmt == chars_format::fixed) {
+    // Example: _Output == 1729, __olength == 4
+
+    // _Ryu_exponent | Printed  | _Whole_digits | _Total_fixed_length  | Notes
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //             2 | 172900   |  6            | _Whole_digits        | Ryu can't be used for printing
+    //             1 | 17290    |  5            | (sometimes adjusted) | when the trimmed digits are nonzero.
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //             0 | 1729     |  4            | _Whole_digits        | Unified length cases.
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //            -1 | 172.9    |  3            | __olength + 1        | This case can't happen for
+    //            -2 | 17.29    |  2            |                      | __olength == 1, but no additional
+    //            -3 | 1.729    |  1            |                      | code is needed to avoid it.
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //            -4 | 0.1729   |  0            | 2 - _Ryu_exponent    | C11 7.21.6.1 "The fprintf function"/8:
+    //            -5 | 0.01729  | -1            |                      | "If a decimal-point character appears,
+    //            -6 | 0.001729 | -2            |                      | at least one digit appears before it."
+
+    const int32_t _Whole_digits = static_cast<int32_t>(__olength) + _Ryu_exponent;
+
+    uint32_t _Total_fixed_length;
+    if (_Ryu_exponent >= 0) { // cases "172900" and "1729"
+      _Total_fixed_length = static_cast<uint32_t>(_Whole_digits);
+      if (_Output == 1) {
+        // Rounding can affect the number of digits.
+        // For example, 1e23 is exactly "99999999999999991611392" which is 23 digits instead of 24.
+        // We can use a lookup table to detect this and adjust the total length.
+        static constexpr uint8_t _Adjustment[309] = {
+          0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,1,0,0,0,1,1,0,1,0,1,1,1,0,1,1,1,0,0,0,0,0,
+          1,1,0,0,1,0,1,1,1,0,0,0,0,1,1,1,1,0,0,0,1,1,1,1,0,0,0,1,1,1,1,0,1,0,1,0,1,1,0,0,0,0,1,1,1,
+          1,0,0,0,0,0,0,0,1,1,0,1,1,0,0,1,0,1,0,1,0,1,1,0,0,0,0,0,1,1,1,0,0,1,1,1,1,1,0,1,0,1,1,0,1,
+          1,0,0,0,0,0,0,0,0,0,1,1,1,0,0,1,0,0,1,0,0,1,1,1,1,0,0,1,1,0,1,1,0,1,1,0,1,0,0,0,1,0,0,0,1,
+          0,1,0,1,0,1,1,1,0,0,0,0,0,0,1,1,1,1,0,0,1,0,1,1,1,0,0,0,1,0,1,1,1,1,1,1,0,1,0,1,1,0,0,0,1,
+          1,1,0,1,1,0,0,0,1,0,0,0,1,0,1,0,0,0,0,0,0,0,1,0,1,1,0,0,1,1,1,0,0,0,1,0,1,0,0,0,0,0,1,1,0,
+          0,1,0,1,1,1,0,0,1,0,0,0,0,1,0,1,0,0,0,0,0,1,0,1,0,1,1,0,1,0,0,0,0,0,1,1,0,1,0 };
+        _Total_fixed_length -= _Adjustment[_Ryu_exponent];
+        // _Whole_digits doesn't need to be adjusted because these cases won't refer to it later.
+      }
+    } else if (_Whole_digits > 0) { // case "17.29"
+      _Total_fixed_length = __olength + 1;
+    } else { // case "0.001729"
+      _Total_fixed_length = static_cast<uint32_t>(2 - _Ryu_exponent);
+    }
+
+    if (_Last - _First < static_cast<ptrdiff_t>(_Total_fixed_length)) {
+      return { _Last, errc::value_too_large };
+    }
+
+    char* _Mid;
+    if (_Ryu_exponent > 0) { // case "172900"
+      bool _Can_use_ryu;
+
+      if (_Ryu_exponent > 22) { // 10^22 is the largest power of 10 that's exactly representable as a double.
+        _Can_use_ryu = false;
+      } else {
+        // Ryu generated X: __v.__mantissa * 10^_Ryu_exponent
+        // __v.__mantissa == 2^_Trailing_zero_bits * (__v.__mantissa >> _Trailing_zero_bits)
+        // 10^_Ryu_exponent == 2^_Ryu_exponent * 5^_Ryu_exponent
+
+        // _Trailing_zero_bits is [0, 56] (aside: because 2^56 is the largest power of 2
+        // with 17 decimal digits, which is double's round-trip limit.)
+        // _Ryu_exponent is [1, 22].
+        // Normalization adds [2, 52] (aside: at least 2 because the pre-normalized mantissa is at least 5).
+        // This adds up to [3, 130], which is well below double's maximum binary exponent 1023.
+
+        // Therefore, we just need to consider (__v.__mantissa >> _Trailing_zero_bits) * 5^_Ryu_exponent.
+
+        // If that product would exceed 53 bits, then X can't be exactly represented as a double.
+        // (That's not a problem for round-tripping, because X is close enough to the original double,
+        // but X isn't mathematically equal to the original double.) This requires a high-precision fallback.
+
+        // If the product is 53 bits or smaller, then X can be exactly represented as a double (and we don't
+        // need to re-synthesize it; the original double must have been X, because Ryu wouldn't produce the
+        // same output for two different doubles X and Y). This allows Ryu's output to be used (zero-filled).
+
+        // (2^53 - 1) / 5^0 (for indexing), (2^53 - 1) / 5^1, ..., (2^53 - 1) / 5^22
+        static constexpr uint64_t _Max_shifted_mantissa[23] = {
+          9007199254740991u, 1801439850948198u, 360287970189639u, 72057594037927u, 14411518807585u,
+          2882303761517u, 576460752303u, 115292150460u, 23058430092u, 4611686018u, 922337203u, 184467440u,
+          36893488u, 7378697u, 1475739u, 295147u, 59029u, 11805u, 2361u, 472u, 94u, 18u, 3u };
+
+        unsigned long _Trailing_zero_bits;
+#ifdef _LIBCPP_HAS_BITSCAN64
+        (void) _BitScanForward64(&_Trailing_zero_bits, __v.__mantissa); // __v.__mantissa is guaranteed nonzero
+#else // ^^^ 64-bit ^^^ / vvv 32-bit vvv
+        const uint32_t _Low_mantissa = static_cast<uint32_t>(__v.__mantissa);
+        if (_Low_mantissa != 0) {
+          (void) _BitScanForward(&_Trailing_zero_bits, _Low_mantissa);
+        } else {
+          const uint32_t _High_mantissa = static_cast<uint32_t>(__v.__mantissa >> 32); // nonzero here
+          (void) _BitScanForward(&_Trailing_zero_bits, _High_mantissa);
+          _Trailing_zero_bits += 32;
+        }
+#endif // ^^^ 32-bit ^^^
+        const uint64_t _Shifted_mantissa = __v.__mantissa >> _Trailing_zero_bits;
+        _Can_use_ryu = _Shifted_mantissa <= _Max_shifted_mantissa[_Ryu_exponent];
+      }
+
+      if (!_Can_use_ryu) {
+        // Print the integer exactly.
+        // Performance note: This will redundantly perform bounds checking.
+        // Performance note: This will redundantly decompose the IEEE representation.
+        return __d2fixed_buffered_n(_First, _Last, __f, 0);
+      }
+
+      // _Can_use_ryu
+      // Print the decimal digits, left-aligned within [_First, _First + _Total_fixed_length).
+      _Mid = _First + __olength;
+    } else { // cases "1729", "17.29", and "0.001729"
+      // Print the decimal digits, right-aligned within [_First, _First + _Total_fixed_length).
+      _Mid = _First + _Total_fixed_length;
+    }
+
+    // We prefer 32-bit operations, even on 64-bit platforms.
+    // We have at most 17 digits, and uint32_t can store 9 digits.
+    // If _Output doesn't fit into uint32_t, we cut off 8 digits,
+    // so the rest will fit into uint32_t.
+    if ((_Output >> 32) != 0) {
+      // Expensive 64-bit division.
+      const uint64_t __q = __div1e8(_Output);
+      uint32_t __output2 = static_cast<uint32_t>(_Output - 100000000 * __q);
+      _Output = __q;
+
+      const uint32_t __c = __output2 % 10000;
+      __output2 /= 10000;
+      const uint32_t __d = __output2 % 10000;
+      const uint32_t __c0 = (__c % 100) << 1;
+      const uint32_t __c1 = (__c / 100) << 1;
+      const uint32_t __d0 = (__d % 100) << 1;
+      const uint32_t __d1 = (__d / 100) << 1;
+
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c0, 2);
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c1, 2);
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __d0, 2);
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __d1, 2);
+    }
+    uint32_t __output2 = static_cast<uint32_t>(_Output);
+    while (__output2 >= 10000) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+      const uint32_t __c = __output2 - 10000 * (__output2 / 10000);
+#else
+      const uint32_t __c = __output2 % 10000;
+#endif
+      __output2 /= 10000;
+      const uint32_t __c0 = (__c % 100) << 1;
+      const uint32_t __c1 = (__c / 100) << 1;
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c0, 2);
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c1, 2);
+    }
+    if (__output2 >= 100) {
+      const uint32_t __c = (__output2 % 100) << 1;
+      __output2 /= 100;
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c, 2);
+    }
+    if (__output2 >= 10) {
+      const uint32_t __c = __output2 << 1;
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c, 2);
+    } else {
+      *--_Mid = static_cast<char>('0' + __output2);
+    }
+
+    if (_Ryu_exponent > 0) { // case "172900" with _Can_use_ryu
+      // Performance note: it might be more efficient to do this immediately after setting _Mid.
+      _VSTD::memset(_First + __olength, '0', static_cast<size_t>(_Ryu_exponent));
+    } else if (_Ryu_exponent == 0) { // case "1729"
+      // Done!
+    } else if (_Whole_digits > 0) { // case "17.29"
+      // Performance note: moving digits might not be optimal.
+      _VSTD::memmove(_First, _First + 1, static_cast<size_t>(_Whole_digits));
+      _First[_Whole_digits] = '.';
+    } else { // case "0.001729"
+      // Performance note: a larger memset() followed by overwriting '.' might be more efficient.
+      _First[0] = '0';
+      _First[1] = '.';
+      _VSTD::memset(_First + 2, '0', static_cast<size_t>(-_Whole_digits));
+    }
+
+    return { _First + _Total_fixed_length, errc{} };
+  }
+
+  const uint32_t _Total_scientific_length = __olength + (__olength > 1) // digits + possible decimal point
+    + (-100 < _Scientific_exponent && _Scientific_exponent < 100 ? 4 : 5); // + scientific exponent
+  if (_Last - _First < static_cast<ptrdiff_t>(_Total_scientific_length)) {
+    return { _Last, errc::value_too_large };
+  }
+  char* const __result = _First;
+
+  // Print the decimal digits.
+  uint32_t __i = 0;
+  // We prefer 32-bit operations, even on 64-bit platforms.
+  // We have at most 17 digits, and uint32_t can store 9 digits.
+  // If _Output doesn't fit into uint32_t, we cut off 8 digits,
+  // so the rest will fit into uint32_t.
+  if ((_Output >> 32) != 0) {
+    // Expensive 64-bit division.
+    const uint64_t __q = __div1e8(_Output);
+    uint32_t __output2 = static_cast<uint32_t>(_Output) - 100000000 * static_cast<uint32_t>(__q);
+    _Output = __q;
+
+    const uint32_t __c = __output2 % 10000;
+    __output2 /= 10000;
+    const uint32_t __d = __output2 % 10000;
+    const uint32_t __c0 = (__c % 100) << 1;
+    const uint32_t __c1 = (__c / 100) << 1;
+    const uint32_t __d0 = (__d % 100) << 1;
+    const uint32_t __d1 = (__d / 100) << 1;
+    _VSTD::memcpy(__result + __olength - __i - 1, __DIGIT_TABLE + __c0, 2);
+    _VSTD::memcpy(__result + __olength - __i - 3, __DIGIT_TABLE + __c1, 2);
+    _VSTD::memcpy(__result + __olength - __i - 5, __DIGIT_TABLE + __d0, 2);
+    _VSTD::memcpy(__result + __olength - __i - 7, __DIGIT_TABLE + __d1, 2);
+    __i += 8;
+  }
+  uint32_t __output2 = static_cast<uint32_t>(_Output);
+  while (__output2 >= 10000) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+    const uint32_t __c = __output2 - 10000 * (__output2 / 10000);
+#else
+    const uint32_t __c = __output2 % 10000;
+#endif
+    __output2 /= 10000;
+    const uint32_t __c0 = (__c % 100) << 1;
+    const uint32_t __c1 = (__c / 100) << 1;
+    _VSTD::memcpy(__result + __olength - __i - 1, __DIGIT_TABLE + __c0, 2);
+    _VSTD::memcpy(__result + __olength - __i - 3, __DIGIT_TABLE + __c1, 2);
+    __i += 4;
+  }
+  if (__output2 >= 100) {
+    const uint32_t __c = (__output2 % 100) << 1;
+    __output2 /= 100;
+    _VSTD::memcpy(__result + __olength - __i - 1, __DIGIT_TABLE + __c, 2);
+    __i += 2;
+  }
+  if (__output2 >= 10) {
+    const uint32_t __c = __output2 << 1;
+    // We can't use memcpy here: the decimal dot goes between these two digits.
+    __result[2] = __DIGIT_TABLE[__c + 1];
+    __result[0] = __DIGIT_TABLE[__c];
+  } else {
+    __result[0] = static_cast<char>('0' + __output2);
+  }
+
+  // Print decimal point if needed.
+  uint32_t __index;
+  if (__olength > 1) {
+    __result[1] = '.';
+    __index = __olength + 1;
+  } else {
+    __index = 1;
+  }
+
+  // Print the exponent.
+  __result[__index++] = 'e';
+  if (_Scientific_exponent < 0) {
+    __result[__index++] = '-';
+    _Scientific_exponent = -_Scientific_exponent;
+  } else {
+    __result[__index++] = '+';
+  }
+
+  if (_Scientific_exponent >= 100) {
+    const int32_t __c = _Scientific_exponent % 10;
+    _VSTD::memcpy(__result + __index, __DIGIT_TABLE + 2 * (_Scientific_exponent / 10), 2);
+    __result[__index + 2] = static_cast<char>('0' + __c);
+    __index += 3;
+  } else {
+    _VSTD::memcpy(__result + __index, __DIGIT_TABLE + 2 * _Scientific_exponent, 2);
+    __index += 2;
+  }
+
+  return { _First + _Total_scientific_length, errc{} };
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline bool __d2d_small_int(const uint64_t __ieeeMantissa, const uint32_t __ieeeExponent,
+  __floating_decimal_64* const __v) {
+  const uint64_t __m2 = (1ull << __DOUBLE_MANTISSA_BITS) | __ieeeMantissa;
+  const int32_t __e2 = static_cast<int32_t>(__ieeeExponent) - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS;
+
+  if (__e2 > 0) {
+    // f = __m2 * 2^__e2 >= 2^53 is an integer.
+    // Ignore this case for now.
+    return false;
+  }
+
+  if (__e2 < -52) {
+    // f < 1.
+    return false;
+  }
+
+  // Since 2^52 <= __m2 < 2^53 and 0 <= -__e2 <= 52: 1 <= f = __m2 / 2^-__e2 < 2^53.
+  // Test if the lower -__e2 bits of the significand are 0, i.e. whether the fraction is 0.
+  const uint64_t __mask = (1ull << -__e2) - 1;
+  const uint64_t __fraction = __m2 & __mask;
+  if (__fraction != 0) {
+    return false;
+  }
+
+  // f is an integer in the range [1, 2^53).
+  // Note: __mantissa might contain trailing (decimal) 0's.
+  // Note: since 2^53 < 10^16, there is no need to adjust __decimalLength17().
+  __v->__mantissa = __m2 >> -__e2;
+  __v->__exponent = 0;
+  return true;
+}
+
+[[nodiscard]] to_chars_result __d2s_buffered_n(char* const _First, char* const _Last, const double __f,
+  const chars_format _Fmt) {
+
+  // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.
+  const uint64_t __bits = __double_to_bits(__f);
+
+  // Case distinction; exit early for the easy cases.
+  if (__bits == 0) {
+    if (_Fmt == chars_format::scientific) {
+      if (_Last - _First < 5) {
+        return { _Last, errc::value_too_large };
+      }
+
+      _VSTD::memcpy(_First, "0e+00", 5);
+
+      return { _First + 5, errc{} };
+    }
+
+    // Print "0" for chars_format::fixed, chars_format::general, and chars_format{}.
+    if (_First == _Last) {
+      return { _Last, errc::value_too_large };
+    }
+
+    *_First = '0';
+
+    return { _First + 1, errc{} };
+  }
+
+  // Decode __bits into mantissa and exponent.
+  const uint64_t __ieeeMantissa = __bits & ((1ull << __DOUBLE_MANTISSA_BITS) - 1);
+  const uint32_t __ieeeExponent = static_cast<uint32_t>(__bits >> __DOUBLE_MANTISSA_BITS);
+
+  if (_Fmt == chars_format::fixed) {
+    // const uint64_t _Mantissa2 = __ieeeMantissa | (1ull << __DOUBLE_MANTISSA_BITS); // restore implicit bit
+    const int32_t _Exponent2 = static_cast<int32_t>(__ieeeExponent)
+      - __DOUBLE_BIAS - __DOUBLE_MANTISSA_BITS; // bias and normalization
+
+    // Normal values are equal to _Mantissa2 * 2^_Exponent2.
+    // (Subnormals are different, but they'll be rejected by the _Exponent2 test here, so they can be ignored.)
+
+    // For nonzero integers, _Exponent2 >= -52. (The minimum value occurs when _Mantissa2 * 2^_Exponent2 is 1.
+    // In that case, _Mantissa2 is the implicit 1 bit followed by 52 zeros, so _Exponent2 is -52 to shift away
+    // the zeros.) The dense range of exactly representable integers has negative or zero exponents
+    // (as positive exponents make the range non-dense). For that dense range, Ryu will always be used:
+    // every digit is necessary to uniquely identify the value, so Ryu must print them all.
+
+    // Positive exponents are the non-dense range of exactly representable integers. This contains all of the values
+    // for which Ryu can't be used (and a few Ryu-friendly values). We can save time by detecting positive
+    // exponents here and skipping Ryu. Calling __d2fixed_buffered_n() with precision 0 is valid for all integers
+    // (so it's okay if we call it with a Ryu-friendly value).
+    if (_Exponent2 > 0) {
+      return __d2fixed_buffered_n(_First, _Last, __f, 0);
+    }
+  }
+
+  __floating_decimal_64 __v;
+  const bool __isSmallInt = __d2d_small_int(__ieeeMantissa, __ieeeExponent, &__v);
+  if (__isSmallInt) {
+    // For small integers in the range [1, 2^53), __v.__mantissa might contain trailing (decimal) zeros.
+    // For scientific notation we need to move these zeros into the exponent.
+    // (This is not needed for fixed-point notation, so it might be beneficial to trim
+    // trailing zeros in __to_chars only if needed - once fixed-point notation output is implemented.)
+    for (;;) {
+      const uint64_t __q = __div10(__v.__mantissa);
+      const uint32_t __r = static_cast<uint32_t>(__v.__mantissa) - 10 * static_cast<uint32_t>(__q);
+      if (__r != 0) {
+        break;
+      }
+      __v.__mantissa = __q;
+      ++__v.__exponent;
+    }
+  } else {
+    __v = __d2d(__ieeeMantissa, __ieeeExponent);
+  }
+
+  return __to_chars(_First, _Last, __v, _Fmt, __f);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on

libcxx/src/ryu/f2s.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+// Avoid formatting to keep the changes with the original code minimal.
+// clang-format off
+
+#include "__config"
+#include "charconv"
+
+#include "include/ryu/common.h"
+#include "include/ryu/d2fixed.h"
+#include "include/ryu/d2s_intrinsics.h"
+#include "include/ryu/digit_table.h"
+#include "include/ryu/f2s.h"
+#include "include/ryu/ryu.h"
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+inline constexpr int __FLOAT_MANTISSA_BITS = 23;
+inline constexpr int __FLOAT_EXPONENT_BITS = 8;
+inline constexpr int __FLOAT_BIAS = 127;
+
+inline constexpr int __FLOAT_POW5_INV_BITCOUNT = 59;
+inline constexpr uint64_t __FLOAT_POW5_INV_SPLIT[31] = {
+  576460752303423489u, 461168601842738791u, 368934881474191033u, 295147905179352826u,
+  472236648286964522u, 377789318629571618u, 302231454903657294u, 483570327845851670u,
+  386856262276681336u, 309485009821345069u, 495176015714152110u, 396140812571321688u,
+  316912650057057351u, 507060240091291761u, 405648192073033409u, 324518553658426727u,
+  519229685853482763u, 415383748682786211u, 332306998946228969u, 531691198313966350u,
+  425352958651173080u, 340282366920938464u, 544451787073501542u, 435561429658801234u,
+  348449143727040987u, 557518629963265579u, 446014903970612463u, 356811923176489971u,
+  570899077082383953u, 456719261665907162u, 365375409332725730u
+};
+inline constexpr int __FLOAT_POW5_BITCOUNT = 61;
+inline constexpr uint64_t __FLOAT_POW5_SPLIT[47] = {
+  1152921504606846976u, 1441151880758558720u, 1801439850948198400u, 2251799813685248000u,
+  1407374883553280000u, 1759218604441600000u, 2199023255552000000u, 1374389534720000000u,
+  1717986918400000000u, 2147483648000000000u, 1342177280000000000u, 1677721600000000000u,
+  2097152000000000000u, 1310720000000000000u, 1638400000000000000u, 2048000000000000000u,
+  1280000000000000000u, 1600000000000000000u, 2000000000000000000u, 1250000000000000000u,
+  1562500000000000000u, 1953125000000000000u, 1220703125000000000u, 1525878906250000000u,
+  1907348632812500000u, 1192092895507812500u, 1490116119384765625u, 1862645149230957031u,
+  1164153218269348144u, 1455191522836685180u, 1818989403545856475u, 2273736754432320594u,
+  1421085471520200371u, 1776356839400250464u, 2220446049250313080u, 1387778780781445675u,
+  1734723475976807094u, 2168404344971008868u, 1355252715606880542u, 1694065894508600678u,
+  2117582368135750847u, 1323488980084844279u, 1654361225106055349u, 2067951531382569187u,
+  1292469707114105741u, 1615587133892632177u, 2019483917365790221u
+};
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __pow5Factor(uint32_t __value) {
+  uint32_t __count = 0;
+  for (;;) {
+    _LIBCPP_ASSERT(__value != 0, "");
+    const uint32_t __q = __value / 5;
+    const uint32_t __r = __value % 5;
+    if (__r != 0) {
+      break;
+    }
+    __value = __q;
+    ++__count;
+  }
+  return __count;
+}
+
+// Returns true if __value is divisible by 5^__p.
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline bool __multipleOfPowerOf5(const uint32_t __value, const uint32_t __p) {
+  return __pow5Factor(__value) >= __p;
+}
+
+// Returns true if __value is divisible by 2^__p.
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline bool __multipleOfPowerOf2(const uint32_t __value, const uint32_t __p) {
+  _LIBCPP_ASSERT(__value != 0, "");
+  _LIBCPP_ASSERT(__p < 32, "");
+  // __builtin_ctz doesn't appear to be faster here.
+  return (__value & ((1u << __p) - 1)) == 0;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mulShift(const uint32_t __m, const uint64_t __factor, const int32_t __shift) {
+  _LIBCPP_ASSERT(__shift > 32, "");
+
+  // The casts here help MSVC to avoid calls to the __allmul library
+  // function.
+  const uint32_t __factorLo = static_cast<uint32_t>(__factor);
+  const uint32_t __factorHi = static_cast<uint32_t>(__factor >> 32);
+  const uint64_t __bits0 = static_cast<uint64_t>(__m) * __factorLo;
+  const uint64_t __bits1 = static_cast<uint64_t>(__m) * __factorHi;
+
+#ifndef _LIBCPP_64_BIT
+  // On 32-bit platforms we can avoid a 64-bit shift-right since we only
+  // need the upper 32 bits of the result and the shift value is > 32.
+  const uint32_t __bits0Hi = static_cast<uint32_t>(__bits0 >> 32);
+  uint32_t __bits1Lo = static_cast<uint32_t>(__bits1);
+  uint32_t __bits1Hi = static_cast<uint32_t>(__bits1 >> 32);
+  __bits1Lo += __bits0Hi;
+  __bits1Hi += (__bits1Lo < __bits0Hi);
+  const int32_t __s = __shift - 32;
+  return (__bits1Hi << (32 - __s)) | (__bits1Lo >> __s);
+#else // ^^^ 32-bit ^^^ / vvv 64-bit vvv
+  const uint64_t __sum = (__bits0 >> 32) + __bits1;
+  const uint64_t __shiftedSum = __sum >> (__shift - 32);
+  _LIBCPP_ASSERT(__shiftedSum <= UINT32_MAX, "");
+  return static_cast<uint32_t>(__shiftedSum);
+#endif // ^^^ 64-bit ^^^
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mulPow5InvDivPow2(const uint32_t __m, const uint32_t __q, const int32_t __j) {
+  return __mulShift(__m, __FLOAT_POW5_INV_SPLIT[__q], __j);
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline uint32_t __mulPow5divPow2(const uint32_t __m, const uint32_t __i, const int32_t __j) {
+  return __mulShift(__m, __FLOAT_POW5_SPLIT[__i], __j);
+}
+
+// A floating decimal representing m * 10^e.
+struct __floating_decimal_32 {
+  uint32_t __mantissa;
+  int32_t __exponent;
+};
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline __floating_decimal_32 __f2d(const uint32_t __ieeeMantissa, const uint32_t __ieeeExponent) {
+  int32_t __e2;
+  uint32_t __m2;
+  if (__ieeeExponent == 0) {
+    // We subtract 2 so that the bounds computation has 2 additional bits.
+    __e2 = 1 - __FLOAT_BIAS - __FLOAT_MANTISSA_BITS - 2;
+    __m2 = __ieeeMantissa;
+  } else {
+    __e2 = static_cast<int32_t>(__ieeeExponent) - __FLOAT_BIAS - __FLOAT_MANTISSA_BITS - 2;
+    __m2 = (1u << __FLOAT_MANTISSA_BITS) | __ieeeMantissa;
+  }
+  const bool __even = (__m2 & 1) == 0;
+  const bool __acceptBounds = __even;
+
+  // Step 2: Determine the interval of valid decimal representations.
+  const uint32_t __mv = 4 * __m2;
+  const uint32_t __mp = 4 * __m2 + 2;
+  // Implicit bool -> int conversion. True is 1, false is 0.
+  const uint32_t __mmShift = __ieeeMantissa != 0 || __ieeeExponent <= 1;
+  const uint32_t __mm = 4 * __m2 - 1 - __mmShift;
+
+  // Step 3: Convert to a decimal power base using 64-bit arithmetic.
+  uint32_t __vr, __vp, __vm;
+  int32_t __e10;
+  bool __vmIsTrailingZeros = false;
+  bool __vrIsTrailingZeros = false;
+  uint8_t __lastRemovedDigit = 0;
+  if (__e2 >= 0) {
+    const uint32_t __q = __log10Pow2(__e2);
+    __e10 = static_cast<int32_t>(__q);
+    const int32_t __k = __FLOAT_POW5_INV_BITCOUNT + __pow5bits(static_cast<int32_t>(__q)) - 1;
+    const int32_t __i = -__e2 + static_cast<int32_t>(__q) + __k;
+    __vr = __mulPow5InvDivPow2(__mv, __q, __i);
+    __vp = __mulPow5InvDivPow2(__mp, __q, __i);
+    __vm = __mulPow5InvDivPow2(__mm, __q, __i);
+    if (__q != 0 && (__vp - 1) / 10 <= __vm / 10) {
+      // We need to know one removed digit even if we are not going to loop below. We could use
+      // __q = X - 1 above, except that would require 33 bits for the result, and we've found that
+      // 32-bit arithmetic is faster even on 64-bit machines.
+      const int32_t __l = __FLOAT_POW5_INV_BITCOUNT + __pow5bits(static_cast<int32_t>(__q - 1)) - 1;
+      __lastRemovedDigit = static_cast<uint8_t>(__mulPow5InvDivPow2(__mv, __q - 1,
+        -__e2 + static_cast<int32_t>(__q) - 1 + __l) % 10);
+    }
+    if (__q <= 9) {
+      // The largest power of 5 that fits in 24 bits is 5^10, but __q <= 9 seems to be safe as well.
+      // Only one of __mp, __mv, and __mm can be a multiple of 5, if any.
+      if (__mv % 5 == 0) {
+        __vrIsTrailingZeros = __multipleOfPowerOf5(__mv, __q);
+      } else if (__acceptBounds) {
+        __vmIsTrailingZeros = __multipleOfPowerOf5(__mm, __q);
+      } else {
+        __vp -= __multipleOfPowerOf5(__mp, __q);
+      }
+    }
+  } else {
+    const uint32_t __q = __log10Pow5(-__e2);
+    __e10 = static_cast<int32_t>(__q) + __e2;
+    const int32_t __i = -__e2 - static_cast<int32_t>(__q);
+    const int32_t __k = __pow5bits(__i) - __FLOAT_POW5_BITCOUNT;
+    int32_t __j = static_cast<int32_t>(__q) - __k;
+    __vr = __mulPow5divPow2(__mv, static_cast<uint32_t>(__i), __j);
+    __vp = __mulPow5divPow2(__mp, static_cast<uint32_t>(__i), __j);
+    __vm = __mulPow5divPow2(__mm, static_cast<uint32_t>(__i), __j);
+    if (__q != 0 && (__vp - 1) / 10 <= __vm / 10) {
+      __j = static_cast<int32_t>(__q) - 1 - (__pow5bits(__i + 1) - __FLOAT_POW5_BITCOUNT);
+      __lastRemovedDigit = static_cast<uint8_t>(__mulPow5divPow2(__mv, static_cast<uint32_t>(__i + 1), __j) % 10);
+    }
+    if (__q <= 1) {
+      // {__vr,__vp,__vm} is trailing zeros if {__mv,__mp,__mm} has at least __q trailing 0 bits.
+      // __mv = 4 * __m2, so it always has at least two trailing 0 bits.
+      __vrIsTrailingZeros = true;
+      if (__acceptBounds) {
+        // __mm = __mv - 1 - __mmShift, so it has 1 trailing 0 bit iff __mmShift == 1.
+        __vmIsTrailingZeros = __mmShift == 1;
+      } else {
+        // __mp = __mv + 2, so it always has at least one trailing 0 bit.
+        --__vp;
+      }
+    } else if (__q < 31) { // TRANSITION(ulfjack): Use a tighter bound here.
+      __vrIsTrailingZeros = __multipleOfPowerOf2(__mv, __q - 1);
+    }
+  }
+
+  // Step 4: Find the shortest decimal representation in the interval of valid representations.
+  int32_t __removed = 0;
+  uint32_t _Output;
+  if (__vmIsTrailingZeros || __vrIsTrailingZeros) {
+    // General case, which happens rarely (~4.0%).
+    while (__vp / 10 > __vm / 10) {
+#ifdef __clang__ // TRANSITION, LLVM-23106
+      __vmIsTrailingZeros &= __vm - (__vm / 10) * 10 == 0;
+#else
+      __vmIsTrailingZeros &= __vm % 10 == 0;
+#endif
+      __vrIsTrailingZeros &= __lastRemovedDigit == 0;
+      __lastRemovedDigit = static_cast<uint8_t>(__vr % 10);
+      __vr /= 10;
+      __vp /= 10;
+      __vm /= 10;
+      ++__removed;
+    }
+    if (__vmIsTrailingZeros) {
+      while (__vm % 10 == 0) {
+        __vrIsTrailingZeros &= __lastRemovedDigit == 0;
+        __lastRemovedDigit = static_cast<uint8_t>(__vr % 10);
+        __vr /= 10;
+        __vp /= 10;
+        __vm /= 10;
+        ++__removed;
+      }
+    }
+    if (__vrIsTrailingZeros && __lastRemovedDigit == 5 && __vr % 2 == 0) {
+      // Round even if the exact number is .....50..0.
+      __lastRemovedDigit = 4;
+    }
+    // We need to take __vr + 1 if __vr is outside bounds or we need to round up.
+    _Output = __vr + ((__vr == __vm && (!__acceptBounds || !__vmIsTrailingZeros)) || __lastRemovedDigit >= 5);
+  } else {
+    // Specialized for the common case (~96.0%). Percentages below are relative to this.
+    // Loop iterations below (approximately):
+    // 0: 13.6%, 1: 70.7%, 2: 14.1%, 3: 1.39%, 4: 0.14%, 5+: 0.01%
+    while (__vp / 10 > __vm / 10) {
+      __lastRemovedDigit = static_cast<uint8_t>(__vr % 10);
+      __vr /= 10;
+      __vp /= 10;
+      __vm /= 10;
+      ++__removed;
+    }
+    // We need to take __vr + 1 if __vr is outside bounds or we need to round up.
+    _Output = __vr + (__vr == __vm || __lastRemovedDigit >= 5);
+  }
+  const int32_t __exp = __e10 + __removed;
+
+  __floating_decimal_32 __fd;
+  __fd.__exponent = __exp;
+  __fd.__mantissa = _Output;
+  return __fd;
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline to_chars_result _Large_integer_to_chars(char* const _First, char* const _Last,
+  const uint32_t _Mantissa2, const int32_t _Exponent2) {
+
+  // Print the integer _Mantissa2 * 2^_Exponent2 exactly.
+
+  // For nonzero integers, _Exponent2 >= -23. (The minimum value occurs when _Mantissa2 * 2^_Exponent2 is 1.
+  // In that case, _Mantissa2 is the implicit 1 bit followed by 23 zeros, so _Exponent2 is -23 to shift away
+  // the zeros.) The dense range of exactly representable integers has negative or zero exponents
+  // (as positive exponents make the range non-dense). For that dense range, Ryu will always be used:
+  // every digit is necessary to uniquely identify the value, so Ryu must print them all.
+
+  // Positive exponents are the non-dense range of exactly representable integers.
+  // This contains all of the values for which Ryu can't be used (and a few Ryu-friendly values).
+
+  // Performance note: Long division appears to be faster than losslessly widening float to double and calling
+  // __d2fixed_buffered_n(). If __f2fixed_buffered_n() is implemented, it might be faster than long division.
+
+  _LIBCPP_ASSERT(_Exponent2 > 0, "");
+  _LIBCPP_ASSERT(_Exponent2 <= 104, ""); // because __ieeeExponent <= 254
+
+  // Manually represent _Mantissa2 * 2^_Exponent2 as a large integer. _Mantissa2 is always 24 bits
+  // (due to the implicit bit), while _Exponent2 indicates a shift of at most 104 bits.
+  // 24 + 104 equals 128 equals 4 * 32, so we need exactly 4 32-bit elements.
+  // We use a little-endian representation, visualized like this:
+
+  // << left shift <<
+  // most significant
+  // _Data[3] _Data[2] _Data[1] _Data[0]
+  //                   least significant
+  //                   >> right shift >>
+
+  constexpr uint32_t _Data_size = 4;
+  uint32_t _Data[_Data_size]{};
+
+  // _Maxidx is the index of the most significant nonzero element.
+  uint32_t _Maxidx = ((24 + static_cast<uint32_t>(_Exponent2) + 31) / 32) - 1;
+  _LIBCPP_ASSERT(_Maxidx < _Data_size, "");
+
+  const uint32_t _Bit_shift = static_cast<uint32_t>(_Exponent2) % 32;
+  if (_Bit_shift <= 8) { // _Mantissa2's 24 bits don't cross an element boundary
+    _Data[_Maxidx] = _Mantissa2 << _Bit_shift;
+  } else { // _Mantissa2's 24 bits cross an element boundary
+    _Data[_Maxidx - 1] = _Mantissa2 << _Bit_shift;
+    _Data[_Maxidx] = _Mantissa2 >> (32 - _Bit_shift);
+  }
+
+  // If Ryu hasn't determined the total output length, we need to buffer the digits generated from right to left
+  // by long division. The largest possible float is: 340'282346638'528859811'704183484'516925440
+  uint32_t _Blocks[4];
+  int32_t _Filled_blocks = 0;
+  // From left to right, we're going to print:
+  // _Data[0] will be [1, 10] digits.
+  // Then if _Filled_blocks > 0:
+  // _Blocks[_Filled_blocks - 1], ..., _Blocks[0] will be 0-filled 9-digit blocks.
+
+  if (_Maxidx != 0) { // If the integer is actually large, perform long division.
+                      // Otherwise, skip to printing _Data[0].
+    for (;;) {
+      // Loop invariant: _Maxidx != 0 (i.e. the integer is actually large)
+
+      const uint32_t _Most_significant_elem = _Data[_Maxidx];
+      const uint32_t _Initial_remainder = _Most_significant_elem % 1000000000;
+      const uint32_t _Initial_quotient = _Most_significant_elem / 1000000000;
+      _Data[_Maxidx] = _Initial_quotient;
+      uint64_t _Remainder = _Initial_remainder;
+
+      // Process less significant elements.
+      uint32_t _Idx = _Maxidx;
+      do {
+        --_Idx; // Initially, _Remainder is at most 10^9 - 1.
+
+        // Now, _Remainder is at most (10^9 - 1) * 2^32 + 2^32 - 1, simplified to 10^9 * 2^32 - 1.
+        _Remainder = (_Remainder << 32) | _Data[_Idx];
+
+        // floor((10^9 * 2^32 - 1) / 10^9) == 2^32 - 1, so uint32_t _Quotient is lossless.
+        const uint32_t _Quotient = static_cast<uint32_t>(__div1e9(_Remainder));
+
+        // _Remainder is at most 10^9 - 1 again.
+        // For uint32_t truncation, see the __mod1e9() comment in d2s_intrinsics.h.
+        _Remainder = static_cast<uint32_t>(_Remainder) - 1000000000u * _Quotient;
+
+        _Data[_Idx] = _Quotient;
+      } while (_Idx != 0);
+
+      // Store a 0-filled 9-digit block.
+      _Blocks[_Filled_blocks++] = static_cast<uint32_t>(_Remainder);
+
+      if (_Initial_quotient == 0) { // Is the large integer shrinking?
+        --_Maxidx; // log2(10^9) is 29.9, so we can't shrink by more than one element.
+        if (_Maxidx == 0) {
+          break; // We've finished long division. Now we need to print _Data[0].
+        }
+      }
+    }
+  }
+
+  _LIBCPP_ASSERT(_Data[0] != 0, "");
+  for (uint32_t _Idx = 1; _Idx < _Data_size; ++_Idx) {
+    _LIBCPP_ASSERT(_Data[_Idx] == 0, "");
+  }
+
+  const uint32_t _Data_olength = _Data[0] >= 1000000000 ? 10 : __decimalLength9(_Data[0]);
+  const uint32_t _Total_fixed_length = _Data_olength + 9 * _Filled_blocks;
+
+  if (_Last - _First < static_cast<ptrdiff_t>(_Total_fixed_length)) {
+    return { _Last, errc::value_too_large };
+  }
+
+  char* _Result = _First;
+
+  // Print _Data[0]. While it's up to 10 digits,
+  // which is more than Ryu generates, the code below can handle this.
+  __append_n_digits(_Data_olength, _Data[0], _Result);
+  _Result += _Data_olength;
+
+  // Print 0-filled 9-digit blocks.
+  for (int32_t _Idx = _Filled_blocks - 1; _Idx >= 0; --_Idx) {
+    __append_nine_digits(_Blocks[_Idx], _Result);
+    _Result += 9;
+  }
+
+  return { _Result, errc{} };
+}
+
+[[nodiscard]] _LIBCPP_HIDE_FROM_ABI inline to_chars_result __to_chars(char* const _First, char* const _Last, const __floating_decimal_32 __v,
+  chars_format _Fmt, const uint32_t __ieeeMantissa, const uint32_t __ieeeExponent) {
+  // Step 5: Print the decimal representation.
+  uint32_t _Output = __v.__mantissa;
+  int32_t _Ryu_exponent = __v.__exponent;
+  const uint32_t __olength = __decimalLength9(_Output);
+  int32_t _Scientific_exponent = _Ryu_exponent + static_cast<int32_t>(__olength) - 1;
+
+  if (_Fmt == chars_format{}) {
+    int32_t _Lower;
+    int32_t _Upper;
+
+    if (__olength == 1) {
+      // Value | Fixed   | Scientific
+      // 1e-3  | "0.001" | "1e-03"
+      // 1e4   | "10000" | "1e+04"
+      _Lower = -3;
+      _Upper = 4;
+    } else {
+      // Value   | Fixed       | Scientific
+      // 1234e-7 | "0.0001234" | "1.234e-04"
+      // 1234e5  | "123400000" | "1.234e+08"
+      _Lower = -static_cast<int32_t>(__olength + 3);
+      _Upper = 5;
+    }
+
+    if (_Lower <= _Ryu_exponent && _Ryu_exponent <= _Upper) {
+      _Fmt = chars_format::fixed;
+    } else {
+      _Fmt = chars_format::scientific;
+    }
+  } else if (_Fmt == chars_format::general) {
+    // C11 7.21.6.1 "The fprintf function"/8:
+    // "Let P equal [...] 6 if the precision is omitted [...].
+    // Then, if a conversion with style E would have an exponent of X:
+    // - if P > X >= -4, the conversion is with style f [...].
+    // - otherwise, the conversion is with style e [...]."
+    if (-4 <= _Scientific_exponent && _Scientific_exponent < 6) {
+      _Fmt = chars_format::fixed;
+    } else {
+      _Fmt = chars_format::scientific;
+    }
+  }
+
+  if (_Fmt == chars_format::fixed) {
+    // Example: _Output == 1729, __olength == 4
+
+    // _Ryu_exponent | Printed  | _Whole_digits | _Total_fixed_length  | Notes
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //             2 | 172900   |  6            | _Whole_digits        | Ryu can't be used for printing
+    //             1 | 17290    |  5            | (sometimes adjusted) | when the trimmed digits are nonzero.
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //             0 | 1729     |  4            | _Whole_digits        | Unified length cases.
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //            -1 | 172.9    |  3            | __olength + 1        | This case can't happen for
+    //            -2 | 17.29    |  2            |                      | __olength == 1, but no additional
+    //            -3 | 1.729    |  1            |                      | code is needed to avoid it.
+    // --------------|----------|---------------|----------------------|---------------------------------------
+    //            -4 | 0.1729   |  0            | 2 - _Ryu_exponent    | C11 7.21.6.1 "The fprintf function"/8:
+    //            -5 | 0.01729  | -1            |                      | "If a decimal-point character appears,
+    //            -6 | 0.001729 | -2            |                      | at least one digit appears before it."
+
+    const int32_t _Whole_digits = static_cast<int32_t>(__olength) + _Ryu_exponent;
+
+    uint32_t _Total_fixed_length;
+    if (_Ryu_exponent >= 0) { // cases "172900" and "1729"
+      _Total_fixed_length = static_cast<uint32_t>(_Whole_digits);
+      if (_Output == 1) {
+        // Rounding can affect the number of digits.
+        // For example, 1e11f is exactly "99999997952" which is 11 digits instead of 12.
+        // We can use a lookup table to detect this and adjust the total length.
+        static constexpr uint8_t _Adjustment[39] = {
+          0,0,0,0,0,0,0,0,0,0,0,1,1,1,0,1,0,1,1,1,0,0,1,1,0,1,0,1,1,0,0,1,0,1,1,0,1,1,1 };
+        _Total_fixed_length -= _Adjustment[_Ryu_exponent];
+        // _Whole_digits doesn't need to be adjusted because these cases won't refer to it later.
+      }
+    } else if (_Whole_digits > 0) { // case "17.29"
+      _Total_fixed_length = __olength + 1;
+    } else { // case "0.001729"
+      _Total_fixed_length = static_cast<uint32_t>(2 - _Ryu_exponent);
+    }
+
+    if (_Last - _First < static_cast<ptrdiff_t>(_Total_fixed_length)) {
+      return { _Last, errc::value_too_large };
+    }
+
+    char* _Mid;
+    if (_Ryu_exponent > 0) { // case "172900"
+      bool _Can_use_ryu;
+
+      if (_Ryu_exponent > 10) { // 10^10 is the largest power of 10 that's exactly representable as a float.
+        _Can_use_ryu = false;
+      } else {
+        // Ryu generated X: __v.__mantissa * 10^_Ryu_exponent
+        // __v.__mantissa == 2^_Trailing_zero_bits * (__v.__mantissa >> _Trailing_zero_bits)
+        // 10^_Ryu_exponent == 2^_Ryu_exponent * 5^_Ryu_exponent
+
+        // _Trailing_zero_bits is [0, 29] (aside: because 2^29 is the largest power of 2
+        // with 9 decimal digits, which is float's round-trip limit.)
+        // _Ryu_exponent is [1, 10].
+        // Normalization adds [2, 23] (aside: at least 2 because the pre-normalized mantissa is at least 5).
+        // This adds up to [3, 62], which is well below float's maximum binary exponent 127.
+
+        // Therefore, we just need to consider (__v.__mantissa >> _Trailing_zero_bits) * 5^_Ryu_exponent.
+
+        // If that product would exceed 24 bits, then X can't be exactly represented as a float.
+        // (That's not a problem for round-tripping, because X is close enough to the original float,
+        // but X isn't mathematically equal to the original float.) This requires a high-precision fallback.
+
+        // If the product is 24 bits or smaller, then X can be exactly represented as a float (and we don't
+        // need to re-synthesize it; the original float must have been X, because Ryu wouldn't produce the
+        // same output for two different floats X and Y). This allows Ryu's output to be used (zero-filled).
+
+        // (2^24 - 1) / 5^0 (for indexing), (2^24 - 1) / 5^1, ..., (2^24 - 1) / 5^10
+        static constexpr uint32_t _Max_shifted_mantissa[11] = {
+          16777215, 3355443, 671088, 134217, 26843, 5368, 1073, 214, 42, 8, 1 };
+
+        unsigned long _Trailing_zero_bits;
+        (void) _BitScanForward(&_Trailing_zero_bits, __v.__mantissa); // __v.__mantissa is guaranteed nonzero
+        const uint32_t _Shifted_mantissa = __v.__mantissa >> _Trailing_zero_bits;
+        _Can_use_ryu = _Shifted_mantissa <= _Max_shifted_mantissa[_Ryu_exponent];
+      }
+
+      if (!_Can_use_ryu) {
+        const uint32_t _Mantissa2 = __ieeeMantissa | (1u << __FLOAT_MANTISSA_BITS); // restore implicit bit
+        const int32_t _Exponent2 = static_cast<int32_t>(__ieeeExponent)
+          - __FLOAT_BIAS - __FLOAT_MANTISSA_BITS; // bias and normalization
+
+        // Performance note: We've already called Ryu, so this will redundantly perform buffering and bounds checking.
+        return _Large_integer_to_chars(_First, _Last, _Mantissa2, _Exponent2);
+      }
+
+      // _Can_use_ryu
+      // Print the decimal digits, left-aligned within [_First, _First + _Total_fixed_length).
+      _Mid = _First + __olength;
+    } else { // cases "1729", "17.29", and "0.001729"
+      // Print the decimal digits, right-aligned within [_First, _First + _Total_fixed_length).
+      _Mid = _First + _Total_fixed_length;
+    }
+
+    while (_Output >= 10000) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+      const uint32_t __c = _Output - 10000 * (_Output / 10000);
+#else
+      const uint32_t __c = _Output % 10000;
+#endif
+      _Output /= 10000;
+      const uint32_t __c0 = (__c % 100) << 1;
+      const uint32_t __c1 = (__c / 100) << 1;
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c0, 2);
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c1, 2);
+    }
+    if (_Output >= 100) {
+      const uint32_t __c = (_Output % 100) << 1;
+      _Output /= 100;
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c, 2);
+    }
+    if (_Output >= 10) {
+      const uint32_t __c = _Output << 1;
+      _VSTD::memcpy(_Mid -= 2, __DIGIT_TABLE + __c, 2);
+    } else {
+      *--_Mid = static_cast<char>('0' + _Output);
+    }
+
+    if (_Ryu_exponent > 0) { // case "172900" with _Can_use_ryu
+      // Performance note: it might be more efficient to do this immediately after setting _Mid.
+      _VSTD::memset(_First + __olength, '0', static_cast<size_t>(_Ryu_exponent));
+    } else if (_Ryu_exponent == 0) { // case "1729"
+      // Done!
+    } else if (_Whole_digits > 0) { // case "17.29"
+      // Performance note: moving digits might not be optimal.
+      _VSTD::memmove(_First, _First + 1, static_cast<size_t>(_Whole_digits));
+      _First[_Whole_digits] = '.';
+    } else { // case "0.001729"
+      // Performance note: a larger memset() followed by overwriting '.' might be more efficient.
+      _First[0] = '0';
+      _First[1] = '.';
+      _VSTD::memset(_First + 2, '0', static_cast<size_t>(-_Whole_digits));
+    }
+
+    return { _First + _Total_fixed_length, errc{} };
+  }
+
+  const uint32_t _Total_scientific_length =
+    __olength + (__olength > 1) + 4; // digits + possible decimal point + scientific exponent
+  if (_Last - _First < static_cast<ptrdiff_t>(_Total_scientific_length)) {
+    return { _Last, errc::value_too_large };
+  }
+  char* const __result = _First;
+
+  // Print the decimal digits.
+  uint32_t __i = 0;
+  while (_Output >= 10000) {
+#ifdef __clang__ // TRANSITION, LLVM-38217
+    const uint32_t __c = _Output - 10000 * (_Output / 10000);
+#else
+    const uint32_t __c = _Output % 10000;
+#endif
+    _Output /= 10000;
+    const uint32_t __c0 = (__c % 100) << 1;
+    const uint32_t __c1 = (__c / 100) << 1;
+    _VSTD::memcpy(__result + __olength - __i - 1, __DIGIT_TABLE + __c0, 2);
+    _VSTD::memcpy(__result + __olength - __i - 3, __DIGIT_TABLE + __c1, 2);
+    __i += 4;
+  }
+  if (_Output >= 100) {
+    const uint32_t __c = (_Output % 100) << 1;
+    _Output /= 100;
+    _VSTD::memcpy(__result + __olength - __i - 1, __DIGIT_TABLE + __c, 2);
+    __i += 2;
+  }
+  if (_Output >= 10) {
+    const uint32_t __c = _Output << 1;
+    // We can't use memcpy here: the decimal dot goes between these two digits.
+    __result[2] = __DIGIT_TABLE[__c + 1];
+    __result[0] = __DIGIT_TABLE[__c];
+  } else {
+    __result[0] = static_cast<char>('0' + _Output);
+  }
+
+  // Print decimal point if needed.
+  uint32_t __index;
+  if (__olength > 1) {
+    __result[1] = '.';
+    __index = __olength + 1;
+  } else {
+    __index = 1;
+  }
+
+  // Print the exponent.
+  __result[__index++] = 'e';
+  if (_Scientific_exponent < 0) {
+    __result[__index++] = '-';
+    _Scientific_exponent = -_Scientific_exponent;
+  } else {
+    __result[__index++] = '+';
+  }
+
+  _VSTD::memcpy(__result + __index, __DIGIT_TABLE + 2 * _Scientific_exponent, 2);
+  __index += 2;
+
+  return { _First + _Total_scientific_length, errc{} };
+}
+
+[[nodiscard]] to_chars_result __f2s_buffered_n(char* const _First, char* const _Last, const float __f,
+  const chars_format _Fmt) {
+
+  // Step 1: Decode the floating-point number, and unify normalized and subnormal cases.
+  const uint32_t __bits = __float_to_bits(__f);
+
+  // Case distinction; exit early for the easy cases.
+  if (__bits == 0) {
+    if (_Fmt == chars_format::scientific) {
+      if (_Last - _First < 5) {
+        return { _Last, errc::value_too_large };
+      }
+
+      _VSTD::memcpy(_First, "0e+00", 5);
+
+      return { _First + 5, errc{} };
+    }
+
+    // Print "0" for chars_format::fixed, chars_format::general, and chars_format{}.
+    if (_First == _Last) {
+      return { _Last, errc::value_too_large };
+    }
+
+    *_First = '0';
+
+    return { _First + 1, errc{} };
+  }
+
+  // Decode __bits into mantissa and exponent.
+  const uint32_t __ieeeMantissa = __bits & ((1u << __FLOAT_MANTISSA_BITS) - 1);
+  const uint32_t __ieeeExponent = __bits >> __FLOAT_MANTISSA_BITS;
+
+  // When _Fmt == chars_format::fixed and the floating-point number is a large integer,
+  // it's faster to skip Ryu and immediately print the integer exactly.
+  if (_Fmt == chars_format::fixed) {
+    const uint32_t _Mantissa2 = __ieeeMantissa | (1u << __FLOAT_MANTISSA_BITS); // restore implicit bit
+    const int32_t _Exponent2 = static_cast<int32_t>(__ieeeExponent)
+      - __FLOAT_BIAS - __FLOAT_MANTISSA_BITS; // bias and normalization
+
+    // Normal values are equal to _Mantissa2 * 2^_Exponent2.
+    // (Subnormals are different, but they'll be rejected by the _Exponent2 test here, so they can be ignored.)
+
+    if (_Exponent2 > 0) {
+      return _Large_integer_to_chars(_First, _Last, _Mantissa2, _Exponent2);
+    }
+  }
+
+  const __floating_decimal_32 __v = __f2d(__ieeeMantissa, __ieeeExponent);
+  return __to_chars(_First, _Last, __v, _Fmt, __ieeeMantissa, __ieeeExponent);
+}
+
+_LIBCPP_END_NAMESPACE_STD
+
+// clang-format on

libcxx/test/std/utilities/charconv/charconv.msvc/double_fixed_precision_to_chars_test_cases_1.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+
+// This file contains test cases derived from:
+// https://github.com/ulfjack/ryu
+// See xcharconv_ryu.h for the exact commit.
+// (Keep the cgmanifest.json commitHash in sync.)
+
+
+#ifndef DOUBLE_FIXED_PRECISION_TO_CHARS_TEST_CASES_1_HPP
+#define DOUBLE_FIXED_PRECISION_TO_CHARS_TEST_CASES_1_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr DoublePrecisionToCharsTestCase double_fixed_precision_to_chars_test_cases_1[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0, chars_format::fixed, 4, "0.0000"},
+    {-0.0, chars_format::fixed, 4, "-0.0000"},
+    {double_inf, chars_format::fixed, 4, "inf"},
+    {-double_inf, chars_format::fixed, 4, "-inf"},
+    {double_nan, chars_format::fixed, 4, "nan"},
+    {-double_nan, chars_format::fixed, 4, "-nan(ind)"},
+    {double_nan_payload, chars_format::fixed, 4, "nan"},
+    {-double_nan_payload, chars_format::fixed, 4, "-nan"},
+    {1.729, chars_format::fixed, 4, "1.7290"},
+    {-1.729, chars_format::fixed, 4, "-1.7290"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest Basic
+    {0x1.000000001869fp+211, chars_format::fixed, 0,
+        "3291009114715486435425664845573426149758869524108446525879746560"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest Zero
+    {0.0, chars_format::fixed, 4, "0.0000"},
+    {0.0, chars_format::fixed, 3, "0.000"},
+    {0.0, chars_format::fixed, 2, "0.00"},
+    {0.0, chars_format::fixed, 1, "0.0"},
+    {0.0, chars_format::fixed, 0, "0"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest MinMax
+    {0x0.0000000000001p-1022, chars_format::fixed, 1074,
+        "0.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "000000000000000000000000000000000000000000000000000000049406564584124654417656879286822137"
+        "236505980261432476442558568250067550727020875186529983636163599237979656469544571773092665"
+        "671035593979639877479601078187812630071319031140452784581716784898210368871863605699873072"
+        "305000638740915356498438731247339727316961514003171538539807412623856559117102665855668676"
+        "818703956031062493194527159149245532930545654440112748012970999954193198940908041656332452"
+        "475714786901472678015935523861155013480352649347201937902681071074917033322268447533357208"
+        "324319360923828934583680601060115061698097530783422773183292479049825247307763759272478746"
+        "560847782037344696995336470179726777175851256605511991315048911014510378627381672509558373"
+        "89733598993664809941164205702637090279242767544565229087538682506419718265533447265625"},
+
+    {0x1.fffffffffffffp+1023, chars_format::fixed, 0,
+        "179769313486231570814527423731704356798070567525844996598917476803157260780028538760589558"
+        "632766878171540458953514382464234321326889464182768467546703537516986049910576551282076245"
+        "490090389328944075868508455133942304583236903222948165808559332123348274797826204144723168"
+        "738177180919299881250404026184124858368"},
+
+    // Test more corner cases.
+    {0x0.fffffffffffffp-1022, chars_format::fixed, 1074,
+        "0."
+        "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585"
+        "0720088902458687608585988765042311224095946549352480256244000922823569517877588880375915526423097809504343"
+        "1208587738715835729182199302029437922422355981982750124204178896957131179108226104397197960400045489739193"
+        "8079198936081525613113376149842043271751033627391549782731594143828136275113838604094249464942286316695429"
+        "1050802018159266421349966065178030950759130587198464239060686371020051087232827846788436319445158661350412"
+        "2347901479236958520832159762106637540161373658304419360371477835530668283453563400507407304013560296804637"
+        "5918583163124224521599262546494300836851861719422417646455137135420132217031370496583210154654068035397417"
+        "9060225895030235019375197730309457631732108525072993050897615825191597207572324554347709124613174935802817"
+        "34466552734375"}, // max subnormal
+    {0x1p-1022, chars_format::fixed, 1022,
+        "0."
+        "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+        "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585"
+        "0720138309023271733240406421921598046233183055332741688720443481391819585428315901251102056406733973103581"
+        "1005152434161553460108856012385377718821130777993532002330479610147442583636071921565046942503734208375250"
+        "8066506166581589487204911799685916396485006359087701183048747997808877537499494515804516050509153998565824"
+        "7081864511353793580499211598108576605199243335211435239014879569960959128889160299264151106346631339366347"
+        "7586513029371762047325631781485664350872122828637642044846811407613911477062801689853244110024161447421618"
+        "5671661505401542850847167529019031613227788967297073731233340869889831750678388469260927739779728586596549"
+        "41091369095406136467568702398678315290680984617210924625396728515625"}, // min normal
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest RoundToEven
+    {0.125, chars_format::fixed, 3, "0.125"},
+    {0.125, chars_format::fixed, 2, "0.12"},
+    {0.375, chars_format::fixed, 3, "0.375"},
+    {0.375, chars_format::fixed, 2, "0.38"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest RoundToEvenInteger
+    {2.5, chars_format::fixed, 1, "2.5"},
+    {2.5, chars_format::fixed, 0, "2"},
+    {3.5, chars_format::fixed, 1, "3.5"},
+    {3.5, chars_format::fixed, 0, "4"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest NonRoundToEvenScenarios
+    {0.748046875, chars_format::fixed, 3, "0.748"},
+    {0.748046875, chars_format::fixed, 2, "0.75"},
+    {0.748046875, chars_format::fixed, 1, "0.7"}, // 0.75 would round to "0.8", but this is smaller
+
+    {0.2509765625, chars_format::fixed, 3, "0.251"},
+    {0.2509765625, chars_format::fixed, 2, "0.25"},
+    {0.2509765625, chars_format::fixed, 1, "0.3"}, // 0.25 would round to "0.2", but this is larger
+
+    {0x1.0000000000001p-2, chars_format::fixed, 54, "0.250000000000000055511151231257827021181583404541015625"},
+    {0x1.0000000000001p-2, chars_format::fixed, 3, "0.250"},
+    {0x1.0000000000001p-2, chars_format::fixed, 2, "0.25"},
+    {0x1.0000000000001p-2, chars_format::fixed, 1, "0.3"}, // 0.25 would round to "0.2", but this is larger (again)
+
+    // More rounding tests.
+    {9.5, chars_format::fixed, 1, "9.5"},
+    {9.5, chars_format::fixed, 0, "10"},
+    {10.5, chars_format::fixed, 1, "10.5"},
+    {10.5, chars_format::fixed, 0, "10"},
+
+    {1.241, chars_format::fixed, 3, "1.241"},
+    {1.241, chars_format::fixed, 1, "1.2"},
+    {1.251, chars_format::fixed, 3, "1.251"},
+    {1.251, chars_format::fixed, 1, "1.3"},
+    {1.261, chars_format::fixed, 3, "1.261"},
+    {1.261, chars_format::fixed, 1, "1.3"},
+    {1.341, chars_format::fixed, 3, "1.341"},
+    {1.341, chars_format::fixed, 1, "1.3"},
+    {1.351, chars_format::fixed, 3, "1.351"},
+    {1.351, chars_format::fixed, 1, "1.4"},
+    {1.361, chars_format::fixed, 3, "1.361"},
+    {1.361, chars_format::fixed, 1, "1.4"},
+
+    {2.41, chars_format::fixed, 2, "2.41"},
+    {2.41, chars_format::fixed, 0, "2"},
+    {2.51, chars_format::fixed, 2, "2.51"},
+    {2.51, chars_format::fixed, 0, "3"},
+    {2.61, chars_format::fixed, 2, "2.61"},
+    {2.61, chars_format::fixed, 0, "3"},
+    {3.41, chars_format::fixed, 2, "3.41"},
+    {3.41, chars_format::fixed, 0, "3"},
+    {3.51, chars_format::fixed, 2, "3.51"},
+    {3.51, chars_format::fixed, 0, "4"},
+    {3.61, chars_format::fixed, 2, "3.61"},
+    {3.61, chars_format::fixed, 0, "4"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest VaryingPrecision
+    {1729.142857142857, chars_format::fixed, 47, "1729.14285714285711037518922239542007446289062500000"},
+    {1729.142857142857, chars_format::fixed, 46, "1729.1428571428571103751892223954200744628906250000"},
+    {1729.142857142857, chars_format::fixed, 45, "1729.142857142857110375189222395420074462890625000"},
+    {1729.142857142857, chars_format::fixed, 44, "1729.14285714285711037518922239542007446289062500"},
+    {1729.142857142857, chars_format::fixed, 43, "1729.1428571428571103751892223954200744628906250"},
+    {1729.142857142857, chars_format::fixed, 42, "1729.142857142857110375189222395420074462890625"},
+    {1729.142857142857, chars_format::fixed, 41, "1729.14285714285711037518922239542007446289062"},
+    {1729.142857142857, chars_format::fixed, 40, "1729.1428571428571103751892223954200744628906"},
+    {1729.142857142857, chars_format::fixed, 39, "1729.142857142857110375189222395420074462891"},
+    {1729.142857142857, chars_format::fixed, 38, "1729.14285714285711037518922239542007446289"},
+    {1729.142857142857, chars_format::fixed, 37, "1729.1428571428571103751892223954200744629"},
+    {1729.142857142857, chars_format::fixed, 36, "1729.142857142857110375189222395420074463"},
+    {1729.142857142857, chars_format::fixed, 35, "1729.14285714285711037518922239542007446"},
+    {1729.142857142857, chars_format::fixed, 34, "1729.1428571428571103751892223954200745"},
+    {1729.142857142857, chars_format::fixed, 33, "1729.142857142857110375189222395420074"},
+    {1729.142857142857, chars_format::fixed, 32, "1729.14285714285711037518922239542007"},
+    {1729.142857142857, chars_format::fixed, 31, "1729.1428571428571103751892223954201"},
+    {1729.142857142857, chars_format::fixed, 30, "1729.142857142857110375189222395420"},
+    {1729.142857142857, chars_format::fixed, 29, "1729.14285714285711037518922239542"},
+    {1729.142857142857, chars_format::fixed, 28, "1729.1428571428571103751892223954"},
+    {1729.142857142857, chars_format::fixed, 27, "1729.142857142857110375189222395"},
+    {1729.142857142857, chars_format::fixed, 26, "1729.14285714285711037518922240"},
+    {1729.142857142857, chars_format::fixed, 25, "1729.1428571428571103751892224"},
+    {1729.142857142857, chars_format::fixed, 24, "1729.142857142857110375189222"},
+    {1729.142857142857, chars_format::fixed, 23, "1729.14285714285711037518922"},
+    {1729.142857142857, chars_format::fixed, 22, "1729.1428571428571103751892"},
+    {1729.142857142857, chars_format::fixed, 21, "1729.142857142857110375189"},
+    {1729.142857142857, chars_format::fixed, 20, "1729.14285714285711037519"},
+    {1729.142857142857, chars_format::fixed, 19, "1729.1428571428571103752"},
+    {1729.142857142857, chars_format::fixed, 18, "1729.142857142857110375"},
+    {1729.142857142857, chars_format::fixed, 17, "1729.14285714285711038"},
+    {1729.142857142857, chars_format::fixed, 16, "1729.1428571428571104"},
+    {1729.142857142857, chars_format::fixed, 15, "1729.142857142857110"},
+    {1729.142857142857, chars_format::fixed, 14, "1729.14285714285711"},
+    {1729.142857142857, chars_format::fixed, 13, "1729.1428571428571"},
+    {1729.142857142857, chars_format::fixed, 12, "1729.142857142857"},
+    {1729.142857142857, chars_format::fixed, 11, "1729.14285714286"},
+    {1729.142857142857, chars_format::fixed, 10, "1729.1428571429"},
+    {1729.142857142857, chars_format::fixed, 9, "1729.142857143"},
+    {1729.142857142857, chars_format::fixed, 8, "1729.14285714"},
+    {1729.142857142857, chars_format::fixed, 7, "1729.1428571"},
+    {1729.142857142857, chars_format::fixed, 6, "1729.142857"},
+    {1729.142857142857, chars_format::fixed, 5, "1729.14286"},
+    {1729.142857142857, chars_format::fixed, 4, "1729.1429"},
+    {1729.142857142857, chars_format::fixed, 3, "1729.143"},
+    {1729.142857142857, chars_format::fixed, 2, "1729.14"},
+    {1729.142857142857, chars_format::fixed, 1, "1729.1"},
+    {1729.142857142857, chars_format::fixed, 0, "1729"},
+
+    // Negative precision requests 6 digits of precision.
+    {1729.142857142857, chars_format::fixed, -1, "1729.142857"},
+    {1729.142857142857, chars_format::fixed, -2, "1729.142857"},
+    {1729.142857142857, chars_format::fixed, -3, "1729.142857"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest Carrying
+    {0.0009, chars_format::fixed, 4, "0.0009"},
+    {0.0009, chars_format::fixed, 3, "0.001"},
+    {0.0029, chars_format::fixed, 4, "0.0029"},
+    {0.0029, chars_format::fixed, 3, "0.003"},
+    {0.0099, chars_format::fixed, 4, "0.0099"},
+    {0.0099, chars_format::fixed, 3, "0.010"},
+    {0.0299, chars_format::fixed, 4, "0.0299"},
+    {0.0299, chars_format::fixed, 3, "0.030"},
+    {0.0999, chars_format::fixed, 4, "0.0999"},
+    {0.0999, chars_format::fixed, 3, "0.100"},
+    {0.2999, chars_format::fixed, 4, "0.2999"},
+    {0.2999, chars_format::fixed, 3, "0.300"},
+    {0.9999, chars_format::fixed, 4, "0.9999"},
+    {0.9999, chars_format::fixed, 3, "1.000"},
+    {2.9999, chars_format::fixed, 4, "2.9999"},
+    {2.9999, chars_format::fixed, 3, "3.000"},
+    {9.9999, chars_format::fixed, 4, "9.9999"},
+    {9.9999, chars_format::fixed, 3, "10.000"},
+    {29.9999, chars_format::fixed, 4, "29.9999"},
+    {29.9999, chars_format::fixed, 3, "30.000"},
+    {99.9999, chars_format::fixed, 4, "99.9999"},
+    {99.9999, chars_format::fixed, 3, "100.000"},
+    {299.9999, chars_format::fixed, 4, "299.9999"},
+    {299.9999, chars_format::fixed, 3, "300.000"},
+
+    {0.09, chars_format::fixed, 2, "0.09"},
+    {0.09, chars_format::fixed, 1, "0.1"},
+    {0.29, chars_format::fixed, 2, "0.29"},
+    {0.29, chars_format::fixed, 1, "0.3"},
+    {0.99, chars_format::fixed, 2, "0.99"},
+    {0.99, chars_format::fixed, 1, "1.0"},
+    {2.99, chars_format::fixed, 2, "2.99"},
+    {2.99, chars_format::fixed, 1, "3.0"},
+    {9.99, chars_format::fixed, 2, "9.99"},
+    {9.99, chars_format::fixed, 1, "10.0"},
+    {29.99, chars_format::fixed, 2, "29.99"},
+    {29.99, chars_format::fixed, 1, "30.0"},
+    {99.99, chars_format::fixed, 2, "99.99"},
+    {99.99, chars_format::fixed, 1, "100.0"},
+    {299.99, chars_format::fixed, 2, "299.99"},
+    {299.99, chars_format::fixed, 1, "300.0"},
+
+    {0.9, chars_format::fixed, 1, "0.9"},
+    {0.9, chars_format::fixed, 0, "1"},
+    {2.9, chars_format::fixed, 1, "2.9"},
+    {2.9, chars_format::fixed, 0, "3"},
+    {9.9, chars_format::fixed, 1, "9.9"},
+    {9.9, chars_format::fixed, 0, "10"},
+    {29.9, chars_format::fixed, 1, "29.9"},
+    {29.9, chars_format::fixed, 0, "30"},
+    {99.9, chars_format::fixed, 1, "99.9"},
+    {99.9, chars_format::fixed, 0, "100"},
+    {299.9, chars_format::fixed, 1, "299.9"},
+    {299.9, chars_format::fixed, 0, "300"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest RoundingResultZero
+    {0.004, chars_format::fixed, 3, "0.004"},
+    {0.004, chars_format::fixed, 2, "0.00"},
+    {0.4, chars_format::fixed, 1, "0.4"},
+    {0.4, chars_format::fixed, 0, "0"},
+    {0.5, chars_format::fixed, 1, "0.5"},
+    {0.5, chars_format::fixed, 0, "0"},
+
+    // Ryu Printf d2fixed_test.cc D2fixedTest Regression
+    {7.018232e-82, chars_format::fixed, 6, "0.000000"},
+};
+
+#endif // DOUBLE_FIXED_PRECISION_TO_CHARS_TEST_CASES_1_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/double_from_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef DOUBLE_FROM_CHARS_TEST_CASES_HPP
+#define DOUBLE_FROM_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+#include <stddef.h>
+#include <system_error>
+using namespace std;
+
+inline constexpr DoubleFromCharsTestCase double_from_chars_test_cases[] = {
+    {"1.000000000000a000", chars_format::hex, 18, errc{}, 0x1.000000000000ap0}, // exact
+    {"1.000000000000a001", chars_format::hex, 18, errc{}, 0x1.000000000000ap0}, // below midpoint, round down
+    {"1.000000000000a800", chars_format::hex, 18, errc{}, 0x1.000000000000ap0}, // midpoint, round down to even
+    {"1.000000000000a801", chars_format::hex, 18, errc{}, 0x1.000000000000bp0}, // above midpoint, round up
+    {"1.000000000000b000", chars_format::hex, 18, errc{}, 0x1.000000000000bp0}, // exact
+    {"1.000000000000b001", chars_format::hex, 18, errc{}, 0x1.000000000000bp0}, // below midpoint, round down
+    {"1.000000000000b800", chars_format::hex, 18, errc{}, 0x1.000000000000cp0}, // midpoint, round up to even
+    {"1.000000000000b801", chars_format::hex, 18, errc{}, 0x1.000000000000cp0}, // above midpoint, round up
+
+    {"1.00000000000020", chars_format::hex, 16, errc{}, 0x1.0000000000002p0}, // exact
+    {"1.00000000000021", chars_format::hex, 16, errc{}, 0x1.0000000000002p0}, // below midpoint, round down
+    {"1.00000000000028", chars_format::hex, 16, errc{}, 0x1.0000000000002p0}, // midpoint, round down to even
+    {"1.00000000000029", chars_format::hex, 16, errc{}, 0x1.0000000000003p0}, // above midpoint, round up
+    {"1.00000000000030", chars_format::hex, 16, errc{}, 0x1.0000000000003p0}, // exact
+    {"1.00000000000031", chars_format::hex, 16, errc{}, 0x1.0000000000003p0}, // below midpoint, round down
+    {"1.00000000000038", chars_format::hex, 16, errc{}, 0x1.0000000000004p0}, // midpoint, round up to even
+    {"1.00000000000039", chars_format::hex, 16, errc{}, 0x1.0000000000004p0}, // above midpoint, round up
+
+    {"1.00000000000000044408920985006261616945266723632812500000", chars_format::general, 58, errc{},
+        0x1.0000000000002p0}, // exact
+    {"1.00000000000000045796699765787707292474806308746337890625", chars_format::general, 58, errc{},
+        0x1.0000000000002p0}, // below midpoint, round down
+    {"1.00000000000000055511151231257827021181583404541015624999", chars_format::general, 58, errc{},
+        0x1.0000000000002p0}, // below midpoint, round down
+    {"1.00000000000000055511151231257827021181583404541015625000", chars_format::general, 58, errc{},
+        0x1.0000000000002p0}, // midpoint, round down to even
+    {"1.00000000000000055511151231257827021181583404541015625001", chars_format::general, 58, errc{},
+        0x1.0000000000003p0}, // above midpoint, round up
+    {"1.00000000000000056898930012039272696711122989654541015625", chars_format::general, 58, errc{},
+        0x1.0000000000003p0}, // above midpoint, round up
+    {"1.00000000000000066613381477509392425417900085449218750000", chars_format::general, 58, errc{},
+        0x1.0000000000003p0}, // exact
+    {"1.00000000000000068001160258290838100947439670562744140625", chars_format::general, 58, errc{},
+        0x1.0000000000003p0}, // below midpoint, round down
+    {"1.00000000000000077715611723760957829654216766357421874999", chars_format::general, 58, errc{},
+        0x1.0000000000003p0}, // below midpoint, round down
+    {"1.00000000000000077715611723760957829654216766357421875000", chars_format::general, 58, errc{},
+        0x1.0000000000004p0}, // midpoint, round up to even
+    {"1.00000000000000077715611723760957829654216766357421875001", chars_format::general, 58, errc{},
+        0x1.0000000000004p0}, // above midpoint, round up
+    {"1.00000000000000079103390504542403505183756351470947265625", chars_format::general, 58, errc{},
+        0x1.0000000000004p0}, // above midpoint, round up
+
+    // https://www.exploringbinary.com/nondeterministic-floating-point-conversions-in-java/
+    {"0.0000008p-1022", chars_format::hex, 15, errc{}, 0x0.0000008p-1022},
+
+    // VSO-838635 "<charconv>: from_chars() mishandles certain subnormals"
+    // These values change on half-ulp boundaries:
+    // 1 * 2^-1075 ~= 2.47e-324 (half-ulp between zero and min subnormal)
+    // 2 * 2^-1075 ~= 4.94e-324 (min subnormal)
+    // 3 * 2^-1075 ~= 7.41e-324 (half-ulp between min subnormal and next subnormal)
+    // 4 * 2^-1075 ~= 9.88e-324 (next subnormal)
+    {"1."
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111e-324",
+        chars_format::scientific, 1007, errc::result_out_of_range, 0x0.0000000000000p+0},
+    {"2."
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222e-324",
+        chars_format::scientific, 1007, errc::result_out_of_range, 0x0.0000000000000p+0},
+    {"3."
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333333"
+     "3333333333333333333e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000001p-1022},
+    {"4."
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444444"
+     "4444444444444444444e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000001p-1022},
+    {"5."
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555555"
+     "5555555555555555555e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000001p-1022},
+    {"6."
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000001p-1022},
+    {"7."
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000002p-1022},
+    {"8."
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000002p-1022},
+    {"9."
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999e-324",
+        chars_format::scientific, 1007, errc{}, 0x0.0000000000002p-1022},
+
+    // VSO-852024: Test cases for round-to-nearest, ties-to-even.
+    // Consider the values:
+    // A: 0x1.0000000000000p+0 == 1.0000000000000000000000000000000000000000000000000000
+    // X:    (1 + 2^-53) * 2^0 == 1.00000000000000011102230246251565404236316680908203125
+    // B: 0x1.0000000000001p+0 == 1.0000000000000002220446049250313080847263336181640625
+    // X is equidistant from A and B. Because they're tied for being nearest, we need to round to even.
+    // That means rounding down to A, because A's least significant hexit 0 is even.
+    // However, values between X and B aren't tied - they're simply nearer to B, so they need to round up to B.
+    // We need to handle tricky cases like the digits of X, followed by a million 0 digits, followed by a 1 digit.
+    // Similarly:
+    // E:      0x1.ffffffffffffep+0 == 1.999999999999999555910790149937383830547332763671875
+    // Y: (1 + 1 - 3 * 2^-53) * 2^0 == 1.99999999999999966693309261245303787291049957275390625
+    // F:      0x1.fffffffffffffp+0 == 1.9999999999999997779553950749686919152736663818359375
+    // The hexit E is 14 and even, while F is 15 and odd.
+
+    // just below (0 + 2^-53) * 2^-1022: decremented last digit, then appended three 9 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002470"
+     "3282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772"
+     "2858865463328355177969898199387398005390939063150356595155702263922908583924491051844359318028499365361525003"
+     "1937045767824921936562366986365848075700158576926990370631192827955855133292783433840935197801553124659726357"
+     "9574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324"
+     "6736009689513405355374585166611342237666786041621596804619144672918403005300575308490487653917113865916462395"
+     "2491262365388187963623937328042389101867234849766823508986338858792562830275599565752445550725518931369083625"
+     "4779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328124999",
+        chars_format::fixed, 1080, errc::result_out_of_range, 0x0.0000000000000p+0},
+
+    // (0 + 2^-53) * 2^-1022 exactly
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002470"
+     "3282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772"
+     "2858865463328355177969898199387398005390939063150356595155702263922908583924491051844359318028499365361525003"
+     "1937045767824921936562366986365848075700158576926990370631192827955855133292783433840935197801553124659726357"
+     "9574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324"
+     "6736009689513405355374585166611342237666786041621596804619144672918403005300575308490487653917113865916462395"
+     "2491262365388187963623937328042389101867234849766823508986338858792562830275599565752445550725518931369083625"
+     "4779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328125",
+        chars_format::fixed, 1077, errc::result_out_of_range, 0x0.0000000000000p+0},
+
+    // (0 + 2^-53) * 2^-1022 exactly, followed by a thousand 0 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002470"
+     "3282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772"
+     "2858865463328355177969898199387398005390939063150356595155702263922908583924491051844359318028499365361525003"
+     "1937045767824921936562366986365848075700158576926990370631192827955855133292783433840935197801553124659726357"
+     "9574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324"
+     "6736009689513405355374585166611342237666786041621596804619144672918403005300575308490487653917113865916462395"
+     "2491262365388187963623937328042389101867234849766823508986338858792562830275599565752445550725518931369083625"
+     "4779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328125000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000",
+        chars_format::fixed, 2077, errc::result_out_of_range, 0x0.0000000000000p+0},
+
+    // above (0 + 2^-53) * 2^-1022: appended a thousand 0 digits followed by a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002470"
+     "3282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772"
+     "2858865463328355177969898199387398005390939063150356595155702263922908583924491051844359318028499365361525003"
+     "1937045767824921936562366986365848075700158576926990370631192827955855133292783433840935197801553124659726357"
+     "9574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324"
+     "6736009689513405355374585166611342237666786041621596804619144672918403005300575308490487653917113865916462395"
+     "2491262365388187963623937328042389101867234849766823508986338858792562830275599565752445550725518931369083625"
+     "4779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328125000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00001",
+        chars_format::fixed, 2078, errc{}, 0x0.0000000000001p-1022},
+
+    // above (0 + 2^-53) * 2^-1022: appended a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002470"
+     "3282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772"
+     "2858865463328355177969898199387398005390939063150356595155702263922908583924491051844359318028499365361525003"
+     "1937045767824921936562366986365848075700158576926990370631192827955855133292783433840935197801553124659726357"
+     "9574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324"
+     "6736009689513405355374585166611342237666786041621596804619144672918403005300575308490487653917113865916462395"
+     "2491262365388187963623937328042389101867234849766823508986338858792562830275599565752445550725518931369083625"
+     "47791869486679949683240497058210285131854513962138377228261454376934125320985913276672363281251",
+        chars_format::fixed, 1078, errc{}, 0x0.0000000000001p-1022},
+
+    // above (0 + 2^-53) * 2^-1022: incremented last digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000002470"
+     "3282292062327208828439643411068618252990130716238221279284125033775363510437593264991818081799618989828234772"
+     "2858865463328355177969898199387398005390939063150356595155702263922908583924491051844359318028499365361525003"
+     "1937045767824921936562366986365848075700158576926990370631192827955855133292783433840935197801553124659726357"
+     "9574622766465272827220056374006485499977096599470454020828166226237857393450736339007967761930577506740176324"
+     "6736009689513405355374585166611342237666786041621596804619144672918403005300575308490487653917113865916462395"
+     "2491262365388187963623937328042389101867234849766823508986338858792562830275599565752445550725518931369083625"
+     "4779186948667994968324049705821028513185451396213837722826145437693412532098591327667236328126",
+        chars_format::fixed, 1077, errc{}, 0x0.0000000000001p-1022},
+
+    // just below (0 + 1 - 3 * 2^-53) * 2^-1022: decremented last digit, then appended three 9 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072006419"
+     "9176395546258779936602667813027328296362349540005779643539444484102225369938322261431279727704724131030539099"
+     "2976863718870946851468024222968583977359185141028540361975476844303195813273469348201130421165308554532083149"
+     "3676067608324920106709384047261543474082573017216837765643921010648239116172158852475760231303527077156200284"
+     "1775343298712758123539074213191978739083589771549597066404661620550578925994422322342444472859570416955675758"
+     "5423752417124134805999073137808018133811049489046686648944255834488901008259721496147104204399198556535697531"
+     "0055231935448663898095485089604066035268185282450207861510244351362091237759797852153577038777504570568436147"
+     "5530270683064113556748943345076587312006145811358486831521563686919762403704226016998291015624999",
+        chars_format::fixed, 1080, errc{}, 0x0.ffffffffffffep-1022},
+
+    // (0 + 1 - 3 * 2^-53) * 2^-1022 exactly
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072006419"
+     "9176395546258779936602667813027328296362349540005779643539444484102225369938322261431279727704724131030539099"
+     "2976863718870946851468024222968583977359185141028540361975476844303195813273469348201130421165308554532083149"
+     "3676067608324920106709384047261543474082573017216837765643921010648239116172158852475760231303527077156200284"
+     "1775343298712758123539074213191978739083589771549597066404661620550578925994422322342444472859570416955675758"
+     "5423752417124134805999073137808018133811049489046686648944255834488901008259721496147104204399198556535697531"
+     "0055231935448663898095485089604066035268185282450207861510244351362091237759797852153577038777504570568436147"
+     "5530270683064113556748943345076587312006145811358486831521563686919762403704226016998291015625",
+        chars_format::fixed, 1077, errc{}, 0x0.ffffffffffffep-1022},
+
+    // (0 + 1 - 3 * 2^-53) * 2^-1022 exactly, followed by a thousand 0 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072006419"
+     "9176395546258779936602667813027328296362349540005779643539444484102225369938322261431279727704724131030539099"
+     "2976863718870946851468024222968583977359185141028540361975476844303195813273469348201130421165308554532083149"
+     "3676067608324920106709384047261543474082573017216837765643921010648239116172158852475760231303527077156200284"
+     "1775343298712758123539074213191978739083589771549597066404661620550578925994422322342444472859570416955675758"
+     "5423752417124134805999073137808018133811049489046686648944255834488901008259721496147104204399198556535697531"
+     "0055231935448663898095485089604066035268185282450207861510244351362091237759797852153577038777504570568436147"
+     "5530270683064113556748943345076587312006145811358486831521563686919762403704226016998291015625000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000",
+        chars_format::fixed, 2077, errc{}, 0x0.ffffffffffffep-1022},
+
+    // above (0 + 1 - 3 * 2^-53) * 2^-1022: appended a thousand 0 digits followed by a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072006419"
+     "9176395546258779936602667813027328296362349540005779643539444484102225369938322261431279727704724131030539099"
+     "2976863718870946851468024222968583977359185141028540361975476844303195813273469348201130421165308554532083149"
+     "3676067608324920106709384047261543474082573017216837765643921010648239116172158852475760231303527077156200284"
+     "1775343298712758123539074213191978739083589771549597066404661620550578925994422322342444472859570416955675758"
+     "5423752417124134805999073137808018133811049489046686648944255834488901008259721496147104204399198556535697531"
+     "0055231935448663898095485089604066035268185282450207861510244351362091237759797852153577038777504570568436147"
+     "5530270683064113556748943345076587312006145811358486831521563686919762403704226016998291015625000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00001",
+        chars_format::fixed, 2078, errc{}, 0x0.fffffffffffffp-1022},
+
+    // above (0 + 1 - 3 * 2^-53) * 2^-1022: appended a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072006419"
+     "9176395546258779936602667813027328296362349540005779643539444484102225369938322261431279727704724131030539099"
+     "2976863718870946851468024222968583977359185141028540361975476844303195813273469348201130421165308554532083149"
+     "3676067608324920106709384047261543474082573017216837765643921010648239116172158852475760231303527077156200284"
+     "1775343298712758123539074213191978739083589771549597066404661620550578925994422322342444472859570416955675758"
+     "5423752417124134805999073137808018133811049489046686648944255834488901008259721496147104204399198556535697531"
+     "0055231935448663898095485089604066035268185282450207861510244351362091237759797852153577038777504570568436147"
+     "55302706830641135567489433450765873120061458113584868315215636869197624037042260169982910156251",
+        chars_format::fixed, 1078, errc{}, 0x0.fffffffffffffp-1022},
+
+    // above (0 + 1 - 3 * 2^-53) * 2^-1022: incremented last digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072006419"
+     "9176395546258779936602667813027328296362349540005779643539444484102225369938322261431279727704724131030539099"
+     "2976863718870946851468024222968583977359185141028540361975476844303195813273469348201130421165308554532083149"
+     "3676067608324920106709384047261543474082573017216837765643921010648239116172158852475760231303527077156200284"
+     "1775343298712758123539074213191978739083589771549597066404661620550578925994422322342444472859570416955675758"
+     "5423752417124134805999073137808018133811049489046686648944255834488901008259721496147104204399198556535697531"
+     "0055231935448663898095485089604066035268185282450207861510244351362091237759797852153577038777504570568436147"
+     "5530270683064113556748943345076587312006145811358486831521563686919762403704226016998291015626",
+        chars_format::fixed, 1077, errc{}, 0x0.fffffffffffffp-1022},
+
+    // just below (1 + 2^-53) * 2^-1022: decremented last digit, then appended three 9 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072016301"
+     "2305563795567615250361241457301801308322872404958664760675944619203679411688695321398552054903200090343478188"
+     "4412325572184367563347617020518175998922941393629966742598285899994830148971433555578567693279306015978183162"
+     "1424250679624607852958851992724935776883207324924799248168692322471659649343292587839501022509739575795105716"
+     "0073834364573849432419299709217920738991976169431413149717326525502008499797367678374315520581880443916381057"
+     "2367791175177756227497413804253387084478193655533073867420834526162513029462022730109054820067654020201547112"
+     "0020281397001415752591234401773622442737124681517501897455599786532342558862196115163359241679580296044770649"
+     "4647018477736093430045142168360701364747951396213837722826145437693412532098591327667236328124999",
+        chars_format::fixed, 1080, errc{}, 0x1.0000000000000p-1022},
+
+    // (1 + 2^-53) * 2^-1022 exactly
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072016301"
+     "2305563795567615250361241457301801308322872404958664760675944619203679411688695321398552054903200090343478188"
+     "4412325572184367563347617020518175998922941393629966742598285899994830148971433555578567693279306015978183162"
+     "1424250679624607852958851992724935776883207324924799248168692322471659649343292587839501022509739575795105716"
+     "0073834364573849432419299709217920738991976169431413149717326525502008499797367678374315520581880443916381057"
+     "2367791175177756227497413804253387084478193655533073867420834526162513029462022730109054820067654020201547112"
+     "0020281397001415752591234401773622442737124681517501897455599786532342558862196115163359241679580296044770649"
+     "4647018477736093430045142168360701364747951396213837722826145437693412532098591327667236328125",
+        chars_format::fixed, 1077, errc{}, 0x1.0000000000000p-1022},
+
+    // (1 + 2^-53) * 2^-1022 exactly, followed by a thousand 0 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072016301"
+     "2305563795567615250361241457301801308322872404958664760675944619203679411688695321398552054903200090343478188"
+     "4412325572184367563347617020518175998922941393629966742598285899994830148971433555578567693279306015978183162"
+     "1424250679624607852958851992724935776883207324924799248168692322471659649343292587839501022509739575795105716"
+     "0073834364573849432419299709217920738991976169431413149717326525502008499797367678374315520581880443916381057"
+     "2367791175177756227497413804253387084478193655533073867420834526162513029462022730109054820067654020201547112"
+     "0020281397001415752591234401773622442737124681517501897455599786532342558862196115163359241679580296044770649"
+     "4647018477736093430045142168360701364747951396213837722826145437693412532098591327667236328125000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000",
+        chars_format::fixed, 2077, errc{}, 0x1.0000000000000p-1022},
+
+    // above (1 + 2^-53) * 2^-1022: appended a thousand 0 digits followed by a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072016301"
+     "2305563795567615250361241457301801308322872404958664760675944619203679411688695321398552054903200090343478188"
+     "4412325572184367563347617020518175998922941393629966742598285899994830148971433555578567693279306015978183162"
+     "1424250679624607852958851992724935776883207324924799248168692322471659649343292587839501022509739575795105716"
+     "0073834364573849432419299709217920738991976169431413149717326525502008499797367678374315520581880443916381057"
+     "2367791175177756227497413804253387084478193655533073867420834526162513029462022730109054820067654020201547112"
+     "0020281397001415752591234401773622442737124681517501897455599786532342558862196115163359241679580296044770649"
+     "4647018477736093430045142168360701364747951396213837722826145437693412532098591327667236328125000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00001",
+        chars_format::fixed, 2078, errc{}, 0x1.0000000000001p-1022},
+
+    // above (1 + 2^-53) * 2^-1022: appended a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072016301"
+     "2305563795567615250361241457301801308322872404958664760675944619203679411688695321398552054903200090343478188"
+     "4412325572184367563347617020518175998922941393629966742598285899994830148971433555578567693279306015978183162"
+     "1424250679624607852958851992724935776883207324924799248168692322471659649343292587839501022509739575795105716"
+     "0073834364573849432419299709217920738991976169431413149717326525502008499797367678374315520581880443916381057"
+     "2367791175177756227497413804253387084478193655533073867420834526162513029462022730109054820067654020201547112"
+     "0020281397001415752591234401773622442737124681517501897455599786532342558862196115163359241679580296044770649"
+     "46470184777360934300451421683607013647479513962138377228261454376934125320985913276672363281251",
+        chars_format::fixed, 1078, errc{}, 0x1.0000000000001p-1022},
+
+    // above (1 + 2^-53) * 2^-1022: incremented last digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000022250738585072016301"
+     "2305563795567615250361241457301801308322872404958664760675944619203679411688695321398552054903200090343478188"
+     "4412325572184367563347617020518175998922941393629966742598285899994830148971433555578567693279306015978183162"
+     "1424250679624607852958851992724935776883207324924799248168692322471659649343292587839501022509739575795105716"
+     "0073834364573849432419299709217920738991976169431413149717326525502008499797367678374315520581880443916381057"
+     "2367791175177756227497413804253387084478193655533073867420834526162513029462022730109054820067654020201547112"
+     "0020281397001415752591234401773622442737124681517501897455599786532342558862196115163359241679580296044770649"
+     "4647018477736093430045142168360701364747951396213837722826145437693412532098591327667236328126",
+        chars_format::fixed, 1077, errc{}, 0x1.0000000000001p-1022},
+
+    // just below (1 + 1 - 3 * 2^-53) * 2^-1022: decremented last digit, then appended three 9 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144020250"
+     "8199667279499186358524265859260511351695091228726223124931264069530541271189424317838013700808305231545782515"
+     "4530323827726959236845743044099361970891187471508150509418060480375117378320411851935338796416115205148741308"
+     "3163272520124606023105869053620631175265621765214646643181420505164043632222668006474326056011713528291579642"
+     "2274554896821334728738317548403413978098469341510556195293821919814730032341053661708792231510873354131880491"
+     "1055533902788485678121901775450062980622457102958163711745945687733011032421168917765671370549738710820782247"
+     "7584250967061891687062782163335299376138075114200886249979505279101870966346394401564490729731565935244123171"
+     "5398102212132212018470035807616260163568645811358486831521563686919762403704226016998291015624999",
+        chars_format::fixed, 1080, errc{}, 0x1.ffffffffffffep-1022},
+
+    // (1 + 1 - 3 * 2^-53) * 2^-1022 exactly
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144020250"
+     "8199667279499186358524265859260511351695091228726223124931264069530541271189424317838013700808305231545782515"
+     "4530323827726959236845743044099361970891187471508150509418060480375117378320411851935338796416115205148741308"
+     "3163272520124606023105869053620631175265621765214646643181420505164043632222668006474326056011713528291579642"
+     "2274554896821334728738317548403413978098469341510556195293821919814730032341053661708792231510873354131880491"
+     "1055533902788485678121901775450062980622457102958163711745945687733011032421168917765671370549738710820782247"
+     "7584250967061891687062782163335299376138075114200886249979505279101870966346394401564490729731565935244123171"
+     "5398102212132212018470035807616260163568645811358486831521563686919762403704226016998291015625",
+        chars_format::fixed, 1077, errc{}, 0x1.ffffffffffffep-1022},
+
+    // (1 + 1 - 3 * 2^-53) * 2^-1022 exactly, followed by a thousand 0 digits
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144020250"
+     "8199667279499186358524265859260511351695091228726223124931264069530541271189424317838013700808305231545782515"
+     "4530323827726959236845743044099361970891187471508150509418060480375117378320411851935338796416115205148741308"
+     "3163272520124606023105869053620631175265621765214646643181420505164043632222668006474326056011713528291579642"
+     "2274554896821334728738317548403413978098469341510556195293821919814730032341053661708792231510873354131880491"
+     "1055533902788485678121901775450062980622457102958163711745945687733011032421168917765671370549738710820782247"
+     "7584250967061891687062782163335299376138075114200886249979505279101870966346394401564490729731565935244123171"
+     "5398102212132212018470035807616260163568645811358486831521563686919762403704226016998291015625000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000",
+        chars_format::fixed, 2077, errc{}, 0x1.ffffffffffffep-1022},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^-1022: appended a thousand 0 digits followed by a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144020250"
+     "8199667279499186358524265859260511351695091228726223124931264069530541271189424317838013700808305231545782515"
+     "4530323827726959236845743044099361970891187471508150509418060480375117378320411851935338796416115205148741308"
+     "3163272520124606023105869053620631175265621765214646643181420505164043632222668006474326056011713528291579642"
+     "2274554896821334728738317548403413978098469341510556195293821919814730032341053661708792231510873354131880491"
+     "1055533902788485678121901775450062980622457102958163711745945687733011032421168917765671370549738710820782247"
+     "7584250967061891687062782163335299376138075114200886249979505279101870966346394401564490729731565935244123171"
+     "5398102212132212018470035807616260163568645811358486831521563686919762403704226016998291015625000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00001",
+        chars_format::fixed, 2078, errc{}, 0x1.fffffffffffffp-1022},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^-1022: appended a 1 digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144020250"
+     "8199667279499186358524265859260511351695091228726223124931264069530541271189424317838013700808305231545782515"
+     "4530323827726959236845743044099361970891187471508150509418060480375117378320411851935338796416115205148741308"
+     "3163272520124606023105869053620631175265621765214646643181420505164043632222668006474326056011713528291579642"
+     "2274554896821334728738317548403413978098469341510556195293821919814730032341053661708792231510873354131880491"
+     "1055533902788485678121901775450062980622457102958163711745945687733011032421168917765671370549738710820782247"
+     "7584250967061891687062782163335299376138075114200886249979505279101870966346394401564490729731565935244123171"
+     "53981022121322120184700358076162601635686458113584868315215636869197624037042260169982910156251",
+        chars_format::fixed, 1078, errc{}, 0x1.fffffffffffffp-1022},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^-1022: incremented last digit
+    {"0."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000044501477170144020250"
+     "8199667279499186358524265859260511351695091228726223124931264069530541271189424317838013700808305231545782515"
+     "4530323827726959236845743044099361970891187471508150509418060480375117378320411851935338796416115205148741308"
+     "3163272520124606023105869053620631175265621765214646643181420505164043632222668006474326056011713528291579642"
+     "2274554896821334728738317548403413978098469341510556195293821919814730032341053661708792231510873354131880491"
+     "1055533902788485678121901775450062980622457102958163711745945687733011032421168917765671370549738710820782247"
+     "7584250967061891687062782163335299376138075114200886249979505279101870966346394401564490729731565935244123171"
+     "5398102212132212018470035807616260163568645811358486831521563686919762403704226016998291015626",
+        chars_format::fixed, 1077, errc{}, 0x1.fffffffffffffp-1022},
+
+    // just below (1 + 2^-53) * 2^-33: decremented last digit, then appended three 9 digits
+    {"0.00000000011641532182693482737782207114105741986576081359316958696581423282623291015624999", chars_format::fixed,
+        91, errc{}, 0x1.0000000000000p-33},
+
+    // (1 + 2^-53) * 2^-33 exactly
+    {"0.00000000011641532182693482737782207114105741986576081359316958696581423282623291015625", chars_format::fixed,
+        88, errc{}, 0x1.0000000000000p-33},
+
+    // (1 + 2^-53) * 2^-33 exactly, followed by a thousand 0 digits
+    {"0."
+     "0000000001164153218269348273778220711410574198657608135931695869658142328262329101562500000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+        chars_format::fixed, 1088, errc{}, 0x1.0000000000000p-33},
+
+    // above (1 + 2^-53) * 2^-33: appended a thousand 0 digits followed by a 1 digit
+    {"0."
+     "0000000001164153218269348273778220711410574198657608135931695869658142328262329101562500000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001",
+        chars_format::fixed, 1089, errc{}, 0x1.0000000000001p-33},
+
+    // above (1 + 2^-53) * 2^-33: appended a 1 digit
+    {"0.000000000116415321826934827377822071141057419865760813593169586965814232826232910156251", chars_format::fixed,
+        89, errc{}, 0x1.0000000000001p-33},
+
+    // above (1 + 2^-53) * 2^-33: incremented last digit
+    {"0.00000000011641532182693482737782207114105741986576081359316958696581423282623291015626", chars_format::fixed,
+        88, errc{}, 0x1.0000000000001p-33},
+
+    // just below (1 + 1 - 3 * 2^-53) * 2^-33: decremented last digit, then appended three 9 digits
+    {"0.00000000023283064365386959013215878657682774040271755922049123910255730152130126953124999", chars_format::fixed,
+        91, errc{}, 0x1.ffffffffffffep-33},
+
+    // (1 + 1 - 3 * 2^-53) * 2^-33 exactly
+    {"0.00000000023283064365386959013215878657682774040271755922049123910255730152130126953125", chars_format::fixed,
+        88, errc{}, 0x1.ffffffffffffep-33},
+
+    // (1 + 1 - 3 * 2^-53) * 2^-33 exactly, followed by a thousand 0 digits
+    {"0."
+     "0000000002328306436538695901321587865768277404027175592204912391025573015213012695312500000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000",
+        chars_format::fixed, 1088, errc{}, 0x1.ffffffffffffep-33},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^-33: appended a thousand 0 digits followed by a 1 digit
+    {"0."
+     "0000000002328306436538695901321587865768277404027175592204912391025573015213012695312500000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001",
+        chars_format::fixed, 1089, errc{}, 0x1.fffffffffffffp-33},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^-33: appended a 1 digit
+    {"0.000000000232830643653869590132158786576827740402717559220491239102557301521301269531251", chars_format::fixed,
+        89, errc{}, 0x1.fffffffffffffp-33},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^-33: incremented last digit
+    {"0.00000000023283064365386959013215878657682774040271755922049123910255730152130126953126", chars_format::fixed,
+        88, errc{}, 0x1.fffffffffffffp-33},
+
+    // just below (1 + 2^-53) * 2^0: decremented last digit, then appended three 9 digits
+    {"1.00000000000000011102230246251565404236316680908203124999", chars_format::fixed, 58, errc{},
+        0x1.0000000000000p+0},
+
+    // (1 + 2^-53) * 2^0 exactly
+    {"1.00000000000000011102230246251565404236316680908203125", chars_format::fixed, 55, errc{}, 0x1.0000000000000p+0},
+
+    // (1 + 2^-53) * 2^0 exactly, followed by a thousand 0 digits
+    {"1."
+     "0000000000000001110223024625156540423631668090820312500000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "000000000000000000000000000000000000000000000000000000000000000000000000",
+        chars_format::fixed, 1055, errc{}, 0x1.0000000000000p+0},
+
+    // above (1 + 2^-53) * 2^0: appended a thousand 0 digits followed by a 1 digit
+    {"1."
+     "0000000000000001110223024625156540423631668090820312500000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000001",
+        chars_format::fixed, 1056, errc{}, 0x1.0000000000001p+0},
+
+    // above (1 + 2^-53) * 2^0: appended a 1 digit
+    {"1.000000000000000111022302462515654042363166809082031251", chars_format::fixed, 56, errc{}, 0x1.0000000000001p+0},
+
+    // above (1 + 2^-53) * 2^0: incremented last digit
+    {"1.00000000000000011102230246251565404236316680908203126", chars_format::fixed, 55, errc{}, 0x1.0000000000001p+0},
+
+    // just below (1 + 1 - 3 * 2^-53) * 2^0: decremented last digit, then appended three 9 digits
+    {"1.99999999999999966693309261245303787291049957275390624999", chars_format::fixed, 58, errc{},
+        0x1.ffffffffffffep+0},
+
+    // (1 + 1 - 3 * 2^-53) * 2^0 exactly
+    {"1.99999999999999966693309261245303787291049957275390625", chars_format::fixed, 55, errc{}, 0x1.ffffffffffffep+0},
+
+    // (1 + 1 - 3 * 2^-53) * 2^0 exactly, followed by a thousand 0 digits
+    {"1."
+     "9999999999999996669330926124530378729104995727539062500000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "000000000000000000000000000000000000000000000000000000000000000000000000",
+        chars_format::fixed, 1055, errc{}, 0x1.ffffffffffffep+0},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^0: appended a thousand 0 digits followed by a 1 digit
+    {"1."
+     "9999999999999996669330926124530378729104995727539062500000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000001",
+        chars_format::fixed, 1056, errc{}, 0x1.fffffffffffffp+0},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^0: appended a 1 digit
+    {"1.999999999999999666933092612453037872910499572753906251", chars_format::fixed, 56, errc{}, 0x1.fffffffffffffp+0},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^0: incremented last digit
+    {"1.99999999999999966693309261245303787291049957275390626", chars_format::fixed, 55, errc{}, 0x1.fffffffffffffp+0},
+
+    // just below (1 + 2^-53) * 2^33: decremented last digit, then appended three 9 digits
+    {"8589934592.00000095367431640624999", chars_format::fixed, 34, errc{}, 0x1.0000000000000p+33},
+
+    // (1 + 2^-53) * 2^33 exactly
+    {"8589934592.00000095367431640625", chars_format::fixed, 31, errc{}, 0x1.0000000000000p+33},
+
+    // (1 + 2^-53) * 2^33 exactly, followed by a thousand 0 digits
+    {"8589934592."
+     "0000009536743164062500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "000000000000000000000000000000000000000",
+        chars_format::fixed, 1031, errc{}, 0x1.0000000000000p+33},
+
+    // above (1 + 2^-53) * 2^33: appended a thousand 0 digits followed by a 1 digit
+    {"8589934592."
+     "0000009536743164062500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000001",
+        chars_format::fixed, 1032, errc{}, 0x1.0000000000001p+33},
+
+    // above (1 + 2^-53) * 2^33: appended a 1 digit
+    {"8589934592.000000953674316406251", chars_format::fixed, 32, errc{}, 0x1.0000000000001p+33},
+
+    // above (1 + 2^-53) * 2^33: incremented last digit
+    {"8589934592.00000095367431640626", chars_format::fixed, 31, errc{}, 0x1.0000000000001p+33},
+
+    // just below (1 + 1 - 3 * 2^-53) * 2^33: decremented last digit, then appended three 9 digits
+    {"17179869183.99999713897705078124999", chars_format::fixed, 35, errc{}, 0x1.ffffffffffffep+33},
+
+    // (1 + 1 - 3 * 2^-53) * 2^33 exactly
+    {"17179869183.99999713897705078125", chars_format::fixed, 32, errc{}, 0x1.ffffffffffffep+33},
+
+    // (1 + 1 - 3 * 2^-53) * 2^33 exactly, followed by a thousand 0 digits
+    {"17179869183."
+     "9999971389770507812500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "000000000000000000000000000000000000000",
+        chars_format::fixed, 1032, errc{}, 0x1.ffffffffffffep+33},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^33: appended a thousand 0 digits followed by a 1 digit
+    {"17179869183."
+     "9999971389770507812500000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000001",
+        chars_format::fixed, 1033, errc{}, 0x1.fffffffffffffp+33},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^33: appended a 1 digit
+    {"17179869183.999997138977050781251", chars_format::fixed, 33, errc{}, 0x1.fffffffffffffp+33},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^33: incremented last digit
+    {"17179869183.99999713897705078126", chars_format::fixed, 32, errc{}, 0x1.fffffffffffffp+33},
+
+    // just below (1 + 2^-53) * 2^77: decremented last digit, then appended three 9 digits
+    {"151115727451828663615487.999", chars_format::fixed, 28, errc{}, 0x1.0000000000000p+77},
+
+    // (1 + 2^-53) * 2^77 exactly
+    {"151115727451828663615488", chars_format::fixed, 24, errc{}, 0x1.0000000000000p+77},
+
+    // (1 + 2^-53) * 2^77 exactly, followed by a thousand 0 digits
+    {"151115727451828663615488."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000",
+        chars_format::fixed, 1025, errc{}, 0x1.0000000000000p+77},
+
+    // above (1 + 2^-53) * 2^77: appended a thousand 0 digits followed by a 1 digit
+    {"151115727451828663615488."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00000000000000000001",
+        chars_format::fixed, 1026, errc{}, 0x1.0000000000001p+77},
+
+    // above (1 + 2^-53) * 2^77: appended a 1 digit
+    {"151115727451828663615488.1", chars_format::fixed, 26, errc{}, 0x1.0000000000001p+77},
+
+    // above (1 + 2^-53) * 2^77: incremented last digit
+    {"151115727451828663615489", chars_format::fixed, 24, errc{}, 0x1.0000000000001p+77},
+
+    // just below (1 + 1 - 3 * 2^-53) * 2^77: decremented last digit, then appended three 9 digits
+    {"302231454903657243344895.999", chars_format::fixed, 28, errc{}, 0x1.ffffffffffffep+77},
+
+    // (1 + 1 - 3 * 2^-53) * 2^77 exactly
+    {"302231454903657243344896", chars_format::fixed, 24, errc{}, 0x1.ffffffffffffep+77},
+
+    // (1 + 1 - 3 * 2^-53) * 2^77 exactly, followed by a thousand 0 digits
+    {"302231454903657243344896."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000",
+        chars_format::fixed, 1025, errc{}, 0x1.ffffffffffffep+77},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^77: appended a thousand 0 digits followed by a 1 digit
+    {"302231454903657243344896."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00000000000000000001",
+        chars_format::fixed, 1026, errc{}, 0x1.fffffffffffffp+77},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^77: appended a 1 digit
+    {"302231454903657243344896.1", chars_format::fixed, 26, errc{}, 0x1.fffffffffffffp+77},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^77: incremented last digit
+    {"302231454903657243344897", chars_format::fixed, 24, errc{}, 0x1.fffffffffffffp+77},
+
+    // just below (1 + 2^-53) * 2^1023: decremented last digit, then appended three 9 digits
+    {"8988465674311580536566680721305029496276241413130815897397134275615404541548669375241369800602409693534988440"
+     "3114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859"
+     "063890851407391008830874765563025951597582513936655578157348020066364210154316532161708031.999",
+        chars_format::fixed, 312, errc{}, 0x1.0000000000000p+1023},
+
+    // (1 + 2^-53) * 2^1023 exactly
+    {"8988465674311580536566680721305029496276241413130815897397134275615404541548669375241369800602409693534988440"
+     "3114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859"
+     "063890851407391008830874765563025951597582513936655578157348020066364210154316532161708032",
+        chars_format::fixed, 308, errc{}, 0x1.0000000000000p+1023},
+
+    // (1 + 2^-53) * 2^1023 exactly, followed by a thousand 0 digits
+    {"8988465674311580536566680721305029496276241413130815897397134275615404541548669375241369800602409693534988440"
+     "3114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859"
+     "063890851407391008830874765563025951597582513936655578157348020066364210154316532161708032."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000",
+        chars_format::fixed, 1309, errc{}, 0x1.0000000000000p+1023},
+
+    // above (1 + 2^-53) * 2^1023: appended a thousand 0 digits followed by a 1 digit
+    {"8988465674311580536566680721305029496276241413130815897397134275615404541548669375241369800602409693534988440"
+     "3114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859"
+     "063890851407391008830874765563025951597582513936655578157348020066364210154316532161708032."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00000000000000000001",
+        chars_format::fixed, 1310, errc{}, 0x1.0000000000001p+1023},
+
+    // above (1 + 2^-53) * 2^1023: appended a 1 digit
+    {"8988465674311580536566680721305029496276241413130815897397134275615404541548669375241369800602409693534988440"
+     "3114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859"
+     "063890851407391008830874765563025951597582513936655578157348020066364210154316532161708032.1",
+        chars_format::fixed, 310, errc{}, 0x1.0000000000001p+1023},
+
+    // above (1 + 2^-53) * 2^1023: incremented last digit
+    {"8988465674311580536566680721305029496276241413130815897397134275615404541548669375241369800602409693534988440"
+     "3114202125541629105369684531108613657287705365884742938136589844238179474556051429647415148697857438797685859"
+     "063890851407391008830874765563025951597582513936655578157348020066364210154316532161708033",
+        chars_format::fixed, 308, errc{}, 0x1.0000000000001p+1023},
+
+    // just below (1 + 1 - 3 * 2^-53) * 2^1023: decremented last digit, then appended three 9 digits
+    {"1797693134862315608353258760581052985162070023416521662616611746258695532672923265745300992879465492467506314"
+     "9033587701752208710592698796290627760473556921329019091915239418047621712533496094635638726128664019802903779"
+     "9514183602981511756283727771403830521483963923935633133642802139091669457927874464075218943.999",
+        chars_format::fixed, 313, errc{}, 0x1.ffffffffffffep+1023},
+
+    // (1 + 1 - 3 * 2^-53) * 2^1023 exactly
+    {"1797693134862315608353258760581052985162070023416521662616611746258695532672923265745300992879465492467506314"
+     "9033587701752208710592698796290627760473556921329019091915239418047621712533496094635638726128664019802903779"
+     "9514183602981511756283727771403830521483963923935633133642802139091669457927874464075218944",
+        chars_format::fixed, 309, errc{}, 0x1.ffffffffffffep+1023},
+
+    // (1 + 1 - 3 * 2^-53) * 2^1023 exactly, followed by a thousand 0 digits
+    {"1797693134862315608353258760581052985162070023416521662616611746258695532672923265745300992879465492467506314"
+     "9033587701752208710592698796290627760473556921329019091915239418047621712533496094635638726128664019802903779"
+     "9514183602981511756283727771403830521483963923935633133642802139091669457927874464075218944."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000",
+        chars_format::fixed, 1310, errc{}, 0x1.ffffffffffffep+1023},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^1023: appended a thousand 0 digits followed by a 1 digit
+    {"1797693134862315608353258760581052985162070023416521662616611746258695532672923265745300992879465492467506314"
+     "9033587701752208710592698796290627760473556921329019091915239418047621712533496094635638726128664019802903779"
+     "9514183602981511756283727771403830521483963923935633133642802139091669457927874464075218944."
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "00000000000000000001",
+        chars_format::fixed, 1311, errc{}, 0x1.fffffffffffffp+1023},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^1023: appended a 1 digit
+    {"1797693134862315608353258760581052985162070023416521662616611746258695532672923265745300992879465492467506314"
+     "9033587701752208710592698796290627760473556921329019091915239418047621712533496094635638726128664019802903779"
+     "9514183602981511756283727771403830521483963923935633133642802139091669457927874464075218944.1",
+        chars_format::fixed, 311, errc{}, 0x1.fffffffffffffp+1023},
+
+    // above (1 + 1 - 3 * 2^-53) * 2^1023: incremented last digit
+    {"1797693134862315608353258760581052985162070023416521662616611746258695532672923265745300992879465492467506314"
+     "9033587701752208710592698796290627760473556921329019091915239418047621712533496094635638726128664019802903779"
+     "9514183602981511756283727771403830521483963923935633133642802139091669457927874464075218945",
+        chars_format::fixed, 309, errc{}, 0x1.fffffffffffffp+1023},
+
+    // VSO-852024 also affected hexfloats.
+    {"0.00000000000008p-1022", chars_format::hex, 22, errc::result_out_of_range, 0x0.0000000000000p+0},
+    {"0."
+     "0000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000001p-1022",
+        chars_format::hex, 1023, errc{}, 0x0.0000000000001p-1022},
+
+    {"0.ffffffffffffe8p-1022", chars_format::hex, 22, errc{}, 0x0.ffffffffffffep-1022},
+    {"0."
+     "ffffffffffffe800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000001p-1022",
+        chars_format::hex, 1023, errc{}, 0x0.fffffffffffffp-1022},
+
+    {"1.00000000000008p+0", chars_format::hex, 19, errc{}, 0x1.0000000000000p+0},
+    {"1."
+     "0000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000001p+0",
+        chars_format::hex, 1020, errc{}, 0x1.0000000000001p+0},
+
+    {"1.ffffffffffffe8p+0", chars_format::hex, 19, errc{}, 0x1.ffffffffffffep+0},
+    {"1."
+     "ffffffffffffe800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000001p+0",
+        chars_format::hex, 1020, errc{}, 0x1.fffffffffffffp+0},
+
+    {"1.00000000000008p+1023", chars_format::hex, 22, errc{}, 0x1.0000000000000p+1023},
+    {"1."
+     "0000000000000800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000001p+1023",
+        chars_format::hex, 1023, errc{}, 0x1.0000000000001p+1023},
+
+    {"1.ffffffffffffe8p+1023", chars_format::hex, 22, errc{}, 0x1.ffffffffffffep+1023},
+    {"1."
+     "ffffffffffffe800000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
+     "0000000000000000000000000000000001p+1023",
+        chars_format::hex, 1023, errc{}, 0x1.fffffffffffffp+1023},
+
+    // VSO-733765 "<charconv>: [Feedback] double std::from_chars behavior on exponent out of range"
+    // LWG-3081 "Floating point from_chars API does not distinguish between overflow and underflow"
+    // These test cases exercise every overflow/underflow codepath.
+    {"1e+1000", chars_format::scientific, 7, errc::result_out_of_range, double_inf},
+    {"1e-1000", chars_format::scientific, 7, errc::result_out_of_range, 0.0},
+    {"1.fffffffffffff8p+1023", chars_format::hex, 22, errc::result_out_of_range, double_inf},
+    {"1e+2000", chars_format::scientific, 7, errc::result_out_of_range, double_inf},
+    {"1e-2000", chars_format::scientific, 7, errc::result_out_of_range, 0.0},
+    {"1e+9999", chars_format::scientific, 7, errc::result_out_of_range, double_inf},
+    {"1e-9999", chars_format::scientific, 7, errc::result_out_of_range, 0.0},
+    {"10e+5199", chars_format::scientific, 8, errc::result_out_of_range, double_inf},
+    {"0.001e-5199", chars_format::scientific, 11, errc::result_out_of_range, 0.0},
+};
+
+#endif // DOUBLE_FROM_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/double_hex_precision_to_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef DOUBLE_HEX_PRECISION_TO_CHARS_TEST_CASES_HPP
+#define DOUBLE_HEX_PRECISION_TO_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr DoublePrecisionToCharsTestCase double_hex_precision_to_chars_test_cases[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0, chars_format::hex, 4, "0.0000p+0"},
+    {-0.0, chars_format::hex, 4, "-0.0000p+0"},
+    {double_inf, chars_format::hex, 4, "inf"},
+    {-double_inf, chars_format::hex, 4, "-inf"},
+    {double_nan, chars_format::hex, 4, "nan"},
+    {-double_nan, chars_format::hex, 4, "-nan(ind)"},
+    {double_nan_payload, chars_format::hex, 4, "nan"},
+    {-double_nan_payload, chars_format::hex, 4, "-nan"},
+    {0x1.729p+0, chars_format::hex, 4, "1.7290p+0"},
+    {-0x1.729p+0, chars_format::hex, 4, "-1.7290p+0"},
+
+    // Test hexfloat corner cases.
+    {0x1.728p+0, chars_format::hex, 13, "1.7280000000000p+0"},
+    {0x0.0000000000001p-1022, chars_format::hex, 13, "0.0000000000001p-1022"}, // min subnormal
+    {0x0.fffffffffffffp-1022, chars_format::hex, 13, "0.fffffffffffffp-1022"}, // max subnormal
+    {0x1p-1022, chars_format::hex, 13, "1.0000000000000p-1022"}, // min normal
+    {0x1.fffffffffffffp+1023, chars_format::hex, 13, "1.fffffffffffffp+1023"}, // max normal
+
+    // Test hexfloat exponents.
+    {0x1p-1009, chars_format::hex, 0, "1p-1009"},
+    {0x1p-999, chars_format::hex, 0, "1p-999"},
+    {0x1p-99, chars_format::hex, 0, "1p-99"},
+    {0x1p-9, chars_format::hex, 0, "1p-9"},
+    {0x1p+0, chars_format::hex, 0, "1p+0"},
+    {0x1p+9, chars_format::hex, 0, "1p+9"},
+    {0x1p+99, chars_format::hex, 0, "1p+99"},
+    {0x1p+999, chars_format::hex, 0, "1p+999"},
+    {0x1p+1009, chars_format::hex, 0, "1p+1009"},
+
+    // Test hexfloat hexits.
+    {0x1.01234567p+0, chars_format::hex, 8, "1.01234567p+0"},
+    {0x1.89abcdefp+0, chars_format::hex, 8, "1.89abcdefp+0"},
+
+    // Test varying precision. Negative precision requests full precision, not shortest round-trip.
+    {0x1.1234561234561p+0, chars_format::hex, -2, "1.1234561234561p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, -1, "1.1234561234561p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 0, "1p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 1, "1.1p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 2, "1.12p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 3, "1.123p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 4, "1.1234p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 5, "1.12345p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 6, "1.123456p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 7, "1.1234561p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 8, "1.12345612p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 9, "1.123456123p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 10, "1.1234561234p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 11, "1.12345612345p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 12, "1.123456123456p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 13, "1.1234561234561p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 14, "1.12345612345610p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 15, "1.123456123456100p+0"},
+    {0x1.1234561234561p+0, chars_format::hex, 16, "1.1234561234561000p+0"},
+
+    // Test rounding at every position.
+    {0x1.cccccccccccccp+0, chars_format::hex, 0, "2p+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 1, "1.dp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 2, "1.cdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 3, "1.ccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 4, "1.cccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 5, "1.ccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 6, "1.cccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 7, "1.ccccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 8, "1.cccccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 9, "1.ccccccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 10, "1.cccccccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 11, "1.ccccccccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 12, "1.cccccccccccdp+0"},
+    {0x1.cccccccccccccp+0, chars_format::hex, 13, "1.cccccccccccccp+0"},
+
+    // Test all combinations of least significant bit, round bit, and trailing bits.
+    {0x1.04000p+0, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 0, Trailing 0
+    {0x1.04001p+0, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 0 and Trailing 1 in different hexits
+    {0x1.04200p+0, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 0 and Trailing 1 in same hexit
+    {0x1.04800p+0, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 1, Trailing 0
+    {0x1.04801p+0, chars_format::hex, 2, "1.05p+0"}, // Lsb 0, Round 1 and Trailing 1 in different hexits
+    {0x1.04900p+0, chars_format::hex, 2, "1.05p+0"}, // Lsb 0, Round 1 and Trailing 1 in same hexit
+    {0x1.05000p+0, chars_format::hex, 2, "1.05p+0"}, // Lsb 1, Round 0, Trailing 0
+    {0x1.05001p+0, chars_format::hex, 2, "1.05p+0"}, // Lsb 1, Round 0 and Trailing 1 in different hexits
+    {0x1.05200p+0, chars_format::hex, 2, "1.05p+0"}, // Lsb 1, Round 0 and Trailing 1 in same hexit
+    {0x1.05800p+0, chars_format::hex, 2, "1.06p+0"}, // Lsb 1, Round 1, Trailing 0
+    {0x1.05801p+0, chars_format::hex, 2, "1.06p+0"}, // Lsb 1, Round 1 and Trailing 1 in different hexits
+    {0x1.05900p+0, chars_format::hex, 2, "1.06p+0"}, // Lsb 1, Round 1 and Trailing 1 in same hexit
+
+    // Test carry propagation.
+    {0x1.0affffffffffep+0, chars_format::hex, 12, "1.0b0000000000p+0"},
+
+    // Test carry propagation into the leading hexit.
+    {0x0.fffffffffffffp-1022, chars_format::hex, 12, "1.000000000000p-1022"},
+    {0x1.fffffffffffffp+1023, chars_format::hex, 12, "2.000000000000p+1023"},
+
+    // Test how the leading hexit participates in the rounding decision.
+    {0x0.000p+0, chars_format::hex, 0, "0p+0"},
+    {0x0.001p-1022, chars_format::hex, 0, "0p-1022"},
+    {0x0.200p-1022, chars_format::hex, 0, "0p-1022"},
+    {0x0.800p-1022, chars_format::hex, 0, "0p-1022"},
+    {0x0.801p-1022, chars_format::hex, 0, "1p-1022"},
+    {0x0.900p-1022, chars_format::hex, 0, "1p-1022"},
+    {0x1.000p+0, chars_format::hex, 0, "1p+0"},
+    {0x1.001p+0, chars_format::hex, 0, "1p+0"},
+    {0x1.200p+0, chars_format::hex, 0, "1p+0"},
+    {0x1.800p+0, chars_format::hex, 0, "2p+0"},
+    {0x1.801p+0, chars_format::hex, 0, "2p+0"},
+    {0x1.900p+0, chars_format::hex, 0, "2p+0"},
+};
+
+#endif // DOUBLE_HEX_PRECISION_TO_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/double_scientific_precision_to_chars_test_cases_1.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+
+// This file contains test cases derived from:
+// https://github.com/ulfjack/ryu
+// See xcharconv_ryu.h for the exact commit.
+// (Keep the cgmanifest.json commitHash in sync.)
+
+
+#ifndef DOUBLE_SCIENTIFIC_PRECISION_TO_CHARS_TEST_CASES_1_HPP
+#define DOUBLE_SCIENTIFIC_PRECISION_TO_CHARS_TEST_CASES_1_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr DoublePrecisionToCharsTestCase double_scientific_precision_to_chars_test_cases_1[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0, chars_format::scientific, 4, "0.0000e+00"},
+    {-0.0, chars_format::scientific, 4, "-0.0000e+00"},
+    {double_inf, chars_format::scientific, 4, "inf"},
+    {-double_inf, chars_format::scientific, 4, "-inf"},
+    {double_nan, chars_format::scientific, 4, "nan"},
+    {-double_nan, chars_format::scientific, 4, "-nan(ind)"},
+    {double_nan_payload, chars_format::scientific, 4, "nan"},
+    {-double_nan_payload, chars_format::scientific, 4, "-nan"},
+    {1.729, chars_format::scientific, 4, "1.7290e+00"},
+    {-1.729, chars_format::scientific, 4, "-1.7290e+00"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest Basic
+    {0x1.000000001869fp+211, chars_format::scientific, 62,
+        "3.29100911471548643542566484557342614975886952410844652587974656e+63"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest Zero
+    {0.0, chars_format::scientific, 4, "0.0000e+00"},
+    {0.0, chars_format::scientific, 3, "0.000e+00"},
+    {0.0, chars_format::scientific, 2, "0.00e+00"},
+    {0.0, chars_format::scientific, 1, "0.0e+00"},
+    {0.0, chars_format::scientific, 0, "0e+00"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest MinMax
+    {0x0.0000000000001p-1022, chars_format::scientific, 750,
+        "4.9406564584124654417656879286822137236505980261432476442558568250067550727020875186529983"
+        "636163599237979656469544571773092665671035593979639877479601078187812630071319031140452784"
+        "581716784898210368871863605699873072305000638740915356498438731247339727316961514003171538"
+        "539807412623856559117102665855668676818703956031062493194527159149245532930545654440112748"
+        "012970999954193198940908041656332452475714786901472678015935523861155013480352649347201937"
+        "902681071074917033322268447533357208324319360923828934583680601060115061698097530783422773"
+        "183292479049825247307763759272478746560847782037344696995336470179726777175851256605511991"
+        "315048911014510378627381672509558373897335989936648099411642057026370902792427675445652290"
+        "87538682506419718265533447265625e-324"},
+
+    {0x1.fffffffffffffp+1023, chars_format::scientific, 308,
+        "1.7976931348623157081452742373170435679807056752584499659891747680315726078002853876058955"
+        "863276687817154045895351438246423432132688946418276846754670353751698604991057655128207624"
+        "549009038932894407586850845513394230458323690322294816580855933212334827479782620414472316"
+        "8738177180919299881250404026184124858368e+308"},
+
+    // Test more corner cases.
+    {0x0.fffffffffffffp-1022, chars_format::scientific, 766,
+        "2."
+        "2250738585072008890245868760858598876504231122409594654935248025624400092282356951787758888037591552642309"
+        "7809504343120858773871583572918219930202943792242235598198275012420417889695713117910822610439719796040004"
+        "5489739193807919893608152561311337614984204327175103362739154978273159414382813627511383860409424946494228"
+        "6316695429105080201815926642134996606517803095075913058719846423906068637102005108723282784678843631944515"
+        "8661350412234790147923695852083215976210663754016137365830441936037147783553066828345356340050740730401356"
+        "0296804637591858316312422452159926254649430083685186171942241764645513713542013221703137049658321015465406"
+        "8035397417906022589503023501937519773030945763173210852507299305089761582519159720757232455434770912461317"
+        "493580281734466552734375e-308"}, // max subnormal
+    {0x1p-1022, chars_format::scientific, 714,
+        "2."
+        "2250738585072013830902327173324040642192159804623318305533274168872044348139181958542831590125110205640673"
+        "3973103581100515243416155346010885601238537771882113077799353200233047961014744258363607192156504694250373"
+        "4208375250806650616658158948720491179968591639648500635908770118304874799780887753749949451580451605050915"
+        "3998565824708186451135379358049921159810857660519924333521143523901487956996095912888916029926415110634663"
+        "1339366347758651302937176204732563178148566435087212282863764204484681140761391147706280168985324411002416"
+        "1447421618567166150540154285084716752901903161322778896729707373123334086988983175067838846926092773977972"
+        "858659654941091369095406136467568702398678315290680984617210924625396728515625e-308"}, // min normal
+
+    // Ryu Printf d2fixed_test.cc D2expTest RoundToEven
+    {0.125, chars_format::scientific, 2, "1.25e-01"},
+    {0.125, chars_format::scientific, 1, "1.2e-01"},
+    {0.375, chars_format::scientific, 2, "3.75e-01"},
+    {0.375, chars_format::scientific, 1, "3.8e-01"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest RoundToEvenInteger
+    {2.5, chars_format::scientific, 1, "2.5e+00"},
+    {2.5, chars_format::scientific, 0, "2e+00"},
+    {3.5, chars_format::scientific, 1, "3.5e+00"},
+    {3.5, chars_format::scientific, 0, "4e+00"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest NonRoundToEvenScenarios
+    {0.748046875, chars_format::scientific, 2, "7.48e-01"},
+    {0.748046875, chars_format::scientific, 1, "7.5e-01"},
+    {0.748046875, chars_format::scientific, 0, "7e-01"}, // 0.75 would round to "8e-01", but this is smaller
+
+    {0.2509765625, chars_format::scientific, 2, "2.51e-01"},
+    {0.2509765625, chars_format::scientific, 1, "2.5e-01"},
+    {0.2509765625, chars_format::scientific, 0, "3e-01"}, // 0.25 would round to "2e-01", but this is larger
+
+    {0x1.0000000000001p-2, chars_format::scientific, 53, "2.50000000000000055511151231257827021181583404541015625e-01"},
+    {0x1.0000000000001p-2, chars_format::scientific, 2, "2.50e-01"},
+    {0x1.0000000000001p-2, chars_format::scientific, 1, "2.5e-01"},
+    {0x1.0000000000001p-2, chars_format::scientific, 0,
+        "3e-01"}, // 0.25 would round to "2e-01", but this is larger (again)
+
+    // More rounding tests.
+    {9.5, chars_format::scientific, 1, "9.5e+00"},
+    {9.5, chars_format::scientific, 0, "1e+01"},
+    {10.5, chars_format::scientific, 2, "1.05e+01"},
+    {10.5, chars_format::scientific, 1, "1.0e+01"},
+
+    {1.241, chars_format::scientific, 3, "1.241e+00"},
+    {1.241, chars_format::scientific, 1, "1.2e+00"},
+    {1.251, chars_format::scientific, 3, "1.251e+00"},
+    {1.251, chars_format::scientific, 1, "1.3e+00"},
+    {1.261, chars_format::scientific, 3, "1.261e+00"},
+    {1.261, chars_format::scientific, 1, "1.3e+00"},
+    {1.341, chars_format::scientific, 3, "1.341e+00"},
+    {1.341, chars_format::scientific, 1, "1.3e+00"},
+    {1.351, chars_format::scientific, 3, "1.351e+00"},
+    {1.351, chars_format::scientific, 1, "1.4e+00"},
+    {1.361, chars_format::scientific, 3, "1.361e+00"},
+    {1.361, chars_format::scientific, 1, "1.4e+00"},
+
+    {2.41, chars_format::scientific, 2, "2.41e+00"},
+    {2.41, chars_format::scientific, 0, "2e+00"},
+    {2.51, chars_format::scientific, 2, "2.51e+00"},
+    {2.51, chars_format::scientific, 0, "3e+00"},
+    {2.61, chars_format::scientific, 2, "2.61e+00"},
+    {2.61, chars_format::scientific, 0, "3e+00"},
+    {3.41, chars_format::scientific, 2, "3.41e+00"},
+    {3.41, chars_format::scientific, 0, "3e+00"},
+    {3.51, chars_format::scientific, 2, "3.51e+00"},
+    {3.51, chars_format::scientific, 0, "4e+00"},
+    {3.61, chars_format::scientific, 2, "3.61e+00"},
+    {3.61, chars_format::scientific, 0, "4e+00"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest VaryingPrecision
+    {1729.142857142857, chars_format::scientific, 50, "1.72914285714285711037518922239542007446289062500000e+03"},
+    {1729.142857142857, chars_format::scientific, 49, "1.7291428571428571103751892223954200744628906250000e+03"},
+    {1729.142857142857, chars_format::scientific, 48, "1.729142857142857110375189222395420074462890625000e+03"},
+    {1729.142857142857, chars_format::scientific, 47, "1.72914285714285711037518922239542007446289062500e+03"},
+    {1729.142857142857, chars_format::scientific, 46, "1.7291428571428571103751892223954200744628906250e+03"},
+    {1729.142857142857, chars_format::scientific, 45, "1.729142857142857110375189222395420074462890625e+03"},
+    {1729.142857142857, chars_format::scientific, 44, "1.72914285714285711037518922239542007446289062e+03"},
+    {1729.142857142857, chars_format::scientific, 43, "1.7291428571428571103751892223954200744628906e+03"},
+    {1729.142857142857, chars_format::scientific, 42, "1.729142857142857110375189222395420074462891e+03"},
+    {1729.142857142857, chars_format::scientific, 41, "1.72914285714285711037518922239542007446289e+03"},
+    {1729.142857142857, chars_format::scientific, 40, "1.7291428571428571103751892223954200744629e+03"},
+    {1729.142857142857, chars_format::scientific, 39, "1.729142857142857110375189222395420074463e+03"},
+    {1729.142857142857, chars_format::scientific, 38, "1.72914285714285711037518922239542007446e+03"},
+    {1729.142857142857, chars_format::scientific, 37, "1.7291428571428571103751892223954200745e+03"},
+    {1729.142857142857, chars_format::scientific, 36, "1.729142857142857110375189222395420074e+03"},
+    {1729.142857142857, chars_format::scientific, 35, "1.72914285714285711037518922239542007e+03"},
+    {1729.142857142857, chars_format::scientific, 34, "1.7291428571428571103751892223954201e+03"},
+    {1729.142857142857, chars_format::scientific, 33, "1.729142857142857110375189222395420e+03"},
+    {1729.142857142857, chars_format::scientific, 32, "1.72914285714285711037518922239542e+03"},
+    {1729.142857142857, chars_format::scientific, 31, "1.7291428571428571103751892223954e+03"},
+    {1729.142857142857, chars_format::scientific, 30, "1.729142857142857110375189222395e+03"},
+    {1729.142857142857, chars_format::scientific, 29, "1.72914285714285711037518922240e+03"},
+    {1729.142857142857, chars_format::scientific, 28, "1.7291428571428571103751892224e+03"},
+    {1729.142857142857, chars_format::scientific, 27, "1.729142857142857110375189222e+03"},
+    {1729.142857142857, chars_format::scientific, 26, "1.72914285714285711037518922e+03"},
+    {1729.142857142857, chars_format::scientific, 25, "1.7291428571428571103751892e+03"},
+    {1729.142857142857, chars_format::scientific, 24, "1.729142857142857110375189e+03"},
+    {1729.142857142857, chars_format::scientific, 23, "1.72914285714285711037519e+03"},
+    {1729.142857142857, chars_format::scientific, 22, "1.7291428571428571103752e+03"},
+    {1729.142857142857, chars_format::scientific, 21, "1.729142857142857110375e+03"},
+    {1729.142857142857, chars_format::scientific, 20, "1.72914285714285711038e+03"},
+    {1729.142857142857, chars_format::scientific, 19, "1.7291428571428571104e+03"},
+    {1729.142857142857, chars_format::scientific, 18, "1.729142857142857110e+03"},
+    {1729.142857142857, chars_format::scientific, 17, "1.72914285714285711e+03"},
+    {1729.142857142857, chars_format::scientific, 16, "1.7291428571428571e+03"},
+    {1729.142857142857, chars_format::scientific, 15, "1.729142857142857e+03"},
+    {1729.142857142857, chars_format::scientific, 14, "1.72914285714286e+03"},
+    {1729.142857142857, chars_format::scientific, 13, "1.7291428571429e+03"},
+    {1729.142857142857, chars_format::scientific, 12, "1.729142857143e+03"},
+    {1729.142857142857, chars_format::scientific, 11, "1.72914285714e+03"},
+    {1729.142857142857, chars_format::scientific, 10, "1.7291428571e+03"},
+    {1729.142857142857, chars_format::scientific, 9, "1.729142857e+03"},
+    {1729.142857142857, chars_format::scientific, 8, "1.72914286e+03"},
+    {1729.142857142857, chars_format::scientific, 7, "1.7291429e+03"},
+    {1729.142857142857, chars_format::scientific, 6, "1.729143e+03"},
+    {1729.142857142857, chars_format::scientific, 5, "1.72914e+03"},
+    {1729.142857142857, chars_format::scientific, 4, "1.7291e+03"},
+    {1729.142857142857, chars_format::scientific, 3, "1.729e+03"},
+    {1729.142857142857, chars_format::scientific, 2, "1.73e+03"},
+    {1729.142857142857, chars_format::scientific, 1, "1.7e+03"},
+    {1729.142857142857, chars_format::scientific, 0, "2e+03"},
+
+    // Negative precision requests 6 digits of precision.
+    {1729.142857142857, chars_format::scientific, -1, "1.729143e+03"},
+    {1729.142857142857, chars_format::scientific, -2, "1.729143e+03"},
+    {1729.142857142857, chars_format::scientific, -3, "1.729143e+03"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest Carrying
+    {2.0009, chars_format::scientific, 4, "2.0009e+00"},
+    {2.0009, chars_format::scientific, 3, "2.001e+00"},
+    {2.0029, chars_format::scientific, 4, "2.0029e+00"},
+    {2.0029, chars_format::scientific, 3, "2.003e+00"},
+    {2.0099, chars_format::scientific, 4, "2.0099e+00"},
+    {2.0099, chars_format::scientific, 3, "2.010e+00"},
+    {2.0299, chars_format::scientific, 4, "2.0299e+00"},
+    {2.0299, chars_format::scientific, 3, "2.030e+00"},
+    {2.0999, chars_format::scientific, 4, "2.0999e+00"},
+    {2.0999, chars_format::scientific, 3, "2.100e+00"},
+    {2.2999, chars_format::scientific, 4, "2.2999e+00"},
+    {2.2999, chars_format::scientific, 3, "2.300e+00"},
+    {2.9999, chars_format::scientific, 4, "2.9999e+00"},
+    {2.9999, chars_format::scientific, 3, "3.000e+00"},
+    {9.9999, chars_format::scientific, 4, "9.9999e+00"},
+    {9.9999, chars_format::scientific, 3, "1.000e+01"},
+
+    {2.09, chars_format::scientific, 2, "2.09e+00"},
+    {2.09, chars_format::scientific, 1, "2.1e+00"},
+    {2.29, chars_format::scientific, 2, "2.29e+00"},
+    {2.29, chars_format::scientific, 1, "2.3e+00"},
+    {2.99, chars_format::scientific, 2, "2.99e+00"},
+    {2.99, chars_format::scientific, 1, "3.0e+00"},
+    {9.99, chars_format::scientific, 2, "9.99e+00"},
+    {9.99, chars_format::scientific, 1, "1.0e+01"},
+
+    {2.9, chars_format::scientific, 1, "2.9e+00"},
+    {2.9, chars_format::scientific, 0, "3e+00"},
+    {9.9, chars_format::scientific, 1, "9.9e+00"},
+    {9.9, chars_format::scientific, 0, "1e+01"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest Exponents
+    {9.99e-100, chars_format::scientific, 2, "9.99e-100"},
+    {9.99e-99, chars_format::scientific, 2, "9.99e-99"},
+    {9.99e-10, chars_format::scientific, 2, "9.99e-10"},
+    {9.99e-09, chars_format::scientific, 2, "9.99e-09"},
+    {9.99e-01, chars_format::scientific, 2, "9.99e-01"},
+    {9.99e+00, chars_format::scientific, 2, "9.99e+00"},
+    {9.99e+01, chars_format::scientific, 2, "9.99e+01"},
+    {9.99e+09, chars_format::scientific, 2, "9.99e+09"},
+    {9.99e+10, chars_format::scientific, 2, "9.99e+10"},
+    {9.99e+99, chars_format::scientific, 2, "9.99e+99"},
+    {9.99e+100, chars_format::scientific, 2, "9.99e+100"},
+
+    {9.99e-100, chars_format::scientific, 1, "1.0e-99"},
+    {9.99e-99, chars_format::scientific, 1, "1.0e-98"},
+    {9.99e-10, chars_format::scientific, 1, "1.0e-09"},
+    {9.99e-09, chars_format::scientific, 1, "1.0e-08"},
+    {9.99e-01, chars_format::scientific, 1, "1.0e+00"},
+    {9.99e+00, chars_format::scientific, 1, "1.0e+01"},
+    {9.99e+01, chars_format::scientific, 1, "1.0e+02"},
+    {9.99e+09, chars_format::scientific, 1, "1.0e+10"},
+    {9.99e+10, chars_format::scientific, 1, "1.0e+11"},
+    {9.99e+99, chars_format::scientific, 1, "1.0e+100"},
+    {9.99e+100, chars_format::scientific, 1, "1.0e+101"},
+
+    // Ryu Printf d2fixed_test.cc D2expTest PrintDecimalPoint
+    // These values exercise each codepath.
+    {1e+54, chars_format::scientific, 0, "1e+54"},
+    {1e+54, chars_format::scientific, 1, "1.0e+54"},
+    {1e-63, chars_format::scientific, 0, "1e-63"},
+    {1e-63, chars_format::scientific, 1, "1.0e-63"},
+    {1e+83, chars_format::scientific, 0, "1e+83"},
+    {1e+83, chars_format::scientific, 1, "1.0e+83"},
+
+    // The UCRT had trouble with rounding this value. charconv was never affected, but let's test it anyways.
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 104,
+        "1.09995565999999994887854821710219658911365648587951921896774663603198787416706536331386569598149846892544e+"
+        "104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 18, "1.099955659999999949e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 17, "1.09995565999999995e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 16, "1.0999556599999999e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 15, "1.099955660000000e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 14, "1.09995566000000e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 13, "1.0999556600000e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 12, "1.099955660000e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 11, "1.09995566000e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 10, "1.0999556600e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 9, "1.099955660e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 8, "1.09995566e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 7, "1.0999557e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 6, "1.099956e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 5, "1.09996e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 4, "1.1000e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 3, "1.100e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 2, "1.10e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 1, "1.1e+104"},
+    {0x1.88e2d605edc3dp+345, chars_format::scientific, 0, "1e+104"},
+
+    // More cases that the UCRT had trouble with (e.g. DevCom-1093399).
+    {0x1.8p+62, chars_format::scientific, 16, "6.9175290276410819e+18"},
+    {0x1.0a2742p+17, chars_format::scientific, 5, "1.36271e+05"},
+    {0x1.f8b0f962cdffbp+205, chars_format::scientific, 13, "1.0137595739223e+62"},
+    {0x1.f8b0f962cdffbp+205, chars_format::scientific, 16, "1.0137595739222531e+62"},
+    {0x1.f8b0f962cdffbp+205, chars_format::scientific, 50, "1.01375957392225305727423222620636224221808910954041e+62"},
+    {0x1.f8b0f962cdffbp+205, chars_format::scientific, 54,
+        "1.013759573922253057274232226206362242218089109540405973e+62"},
+};
+
+#endif // DOUBLE_SCIENTIFIC_PRECISION_TO_CHARS_TEST_CASES_1_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/float_fixed_precision_to_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+
+// This file contains test cases derived from:
+// https://github.com/ulfjack/ryu
+// See xcharconv_ryu.h for the exact commit.
+// (Keep the cgmanifest.json commitHash in sync.)
+
+
+#ifndef FLOAT_FIXED_PRECISION_TO_CHARS_TEST_CASES_HPP
+#define FLOAT_FIXED_PRECISION_TO_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr FloatPrecisionToCharsTestCase float_fixed_precision_to_chars_test_cases[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0f, chars_format::fixed, 4, "0.0000"},
+    {-0.0f, chars_format::fixed, 4, "-0.0000"},
+    {float_inf, chars_format::fixed, 4, "inf"},
+    {-float_inf, chars_format::fixed, 4, "-inf"},
+    {float_nan, chars_format::fixed, 4, "nan"},
+    {-float_nan, chars_format::fixed, 4, "-nan(ind)"},
+    {float_nan_payload, chars_format::fixed, 4, "nan"},
+    {-float_nan_payload, chars_format::fixed, 4, "-nan"},
+    {1.729f, chars_format::fixed, 4, "1.7290"},
+    {-1.729f, chars_format::fixed, 4, "-1.7290"},
+
+    // Ryu Printf Zero
+    {0.0f, chars_format::fixed, 4, "0.0000"},
+    {0.0f, chars_format::fixed, 3, "0.000"},
+    {0.0f, chars_format::fixed, 2, "0.00"},
+    {0.0f, chars_format::fixed, 1, "0.0"},
+    {0.0f, chars_format::fixed, 0, "0"},
+
+    // Test corner cases.
+    {0x0.000002p-126f, chars_format::fixed, 149, // min subnormal
+        "0."
+        "0000000000000000000000000000000000000000000014012984643248170709237295832899161312802619418765157717570682"
+        "8388979108268586060148663818836212158203125"},
+    {0x0.fffffep-126f, chars_format::fixed, 149, // max subnormal
+        "0."
+        "0000000000000000000000000000000000000117549421069244107548702944484928734882705242874589333385717453057158"
+        "8870475618904265502351336181163787841796875"},
+    {0x1p-126f, chars_format::fixed, 126, // min normal
+        "0."
+        "0000000000000000000000000000000000000117549435082228750796873653722224567781866555677208752150875170627841"
+        "72594547271728515625"},
+    {0x1.fffffep+127f, chars_format::fixed, 0, // max normal
+        "340282346638528859811704183484516925440"},
+
+    // Ryu Printf AllPowersOfTen
+    // These values test every power of ten that's within the range of floats.
+    {1e-44f, chars_format::fixed, 149,
+        "0."
+        "0000000000000000000000000000000000000000000098090892502737194964661070830294129189618335931356104022994779"
+        "8722853757880102421040646731853485107421875"},
+    {1e-43f, chars_format::fixed, 149,
+        "0."
+        "0000000000000000000000000000000000000000000994921909670620120355848004135840453208985978732326197947518481"
+        "5617516687069610270555131137371063232421875"},
+    {1e-42f, chars_format::fixed, 148,
+        "0."
+        "0000000000000000000000000000000000000000010005271035279193886395429224690001177341070264998322610345467546"
+        "973108330377044694614596664905548095703125"},
+    {1e-41f, chars_format::fixed, 144,
+        "0."
+        "0000000000000000000000000000000000000000099996658414218946181117343063568415128159492172308165472584392738"
+        "37549166046301252208650112152099609375"},
+    {1e-40f, chars_format::fixed, 148,
+        "0."
+        "0000000000000000000000000000000000000000999994610111475958152591905227349949604220526961919185041279068749"
+        "432712426283842432894743978977203369140625"},
+    {1e-39f, chars_format::fixed, 146,
+        "0."
+        "0000000000000000000000000000000000000010000002153053332574208756001456831092687456480096866911043660970225"
+        "6827159061458587530069053173065185546875"},
+    {1e-38f, chars_format::fixed, 148,
+        "0."
+        "0000000000000000000000000000000000000099999993504564039245746141539976645128551939195729831580121174560891"
+        "149363239804870318039320409297943115234375"},
+    {1e-37f, chars_format::fixed, 145,
+        "0."
+        "0000000000000000000000000000000000000999999991097578965450144252348949782882164643167775990861842615891642"
+        "849224041356137604452669620513916015625"},
+    {1e-36f, chars_format::fixed, 143,
+        "0."
+        "0000000000000000000000000000000000010000000359391298238442905219082964481594808441361581309103473121178279"
+        "3369735600208514370024204254150390625"},
+    {1e-35f, chars_format::fixed, 139,
+        "0."
+        "0000000000000000000000000000000000100000001800250948048663201408455778204855436374880527489094543362735389"
+        "990803014370612800121307373046875"},
+    {1e-34f, chars_format::fixed, 136,
+        "0."
+        "0000000000000000000000000000000001000000046701102029858885626602539647826036732368569844521988439212112353"
+        "970951517112553119659423828125"},
+    {1e-33f, chars_format::fixed, 131,
+        "0."
+        "0000000000000000000000000000000010000000237422279903610827365881541552040508374727581888171540347443055907"
+        "2061441838741302490234375"},
+    {1e-32f, chars_format::fixed, 130,
+        "0."
+        "0000000000000000000000000000000100000002374222799036108273658815415520405083747275818881715403474430559072"
+        "061441838741302490234375"},
+    {1e-31f, chars_format::fixed, 126,
+        "0."
+        "0000000000000000000000000000000999999979661189834525301187760534009369837919272799809863871978166116605279"
+        "96718883514404296875"},
+    {1e-30f, chars_format::fixed, 118,
+        "0."
+        "0000000000000000000000000000010000000031710768509710513471352647538147514756461109453056224083411507308483"
+        "123779296875"},
+    {1e-29f, chars_format::fixed, 117,
+        "0."
+        "0000000000000000000000000000100000000317107685097105134713526475381475147564611094530562240834115073084831"
+        "23779296875"},
+    {1e-28f, chars_format::fixed, 116,
+        "0."
+        "0000000000000000000000000001000000003171076850971051347135264753814751475646110945305622408341150730848312"
+        "3779296875"},
+    {1e-27f, chars_format::fixed, 112,
+        "0."
+        "0000000000000000000000000010000000272452011558114995103349890361263429573723815479979748488403856754302978"
+        "515625"},
+    {1e-26f, chars_format::fixed, 109,
+        "0."
+        "0000000000000000000000000099999998872660226806678244921543018442779658661034858369021094404160976409912109"
+        "375"},
+    {1e-25f, chars_format::fixed, 104,
+        "0."
+        "00000000000000000000000010000000195414813782625560981110772657866336832199749551364220678806304931640625"},
+    {1e-24f, chars_format::fixed, 103,
+        "0."
+        "0000000000000000000000010000000195414813782625560981110772657866336832199749551364220678806304931640625"},
+    {1e-23f, chars_format::fixed, 99,
+        "0.000000000000000000000009999999998199587477372609628178631337169779413898140774108469486236572265625"},
+    {1e-22f, chars_format::fixed, 97,
+        "0.0000000000000000000001000000031374394956577733179287005745028427128318071481771767139434814453125"},
+    {1e-21f, chars_format::fixed, 88,
+        "0.0000000000000000000009999999682655225388967887463487205224055287544615566730499267578125"},
+    {1e-20f, chars_format::fixed, 87,
+        "0.000000000000000000009999999682655225388967887463487205224055287544615566730499267578125"},
+    {1e-19f, chars_format::fixed, 86,
+        "0.00000000000000000009999999682655225388967887463487205224055287544615566730499267578125"},
+    {1e-18f, chars_format::fixed, 83,
+        "0.00000000000000000100000004581370496574313326554328540396454627625644207000732421875"},
+    {1e-17f, chars_format::fixed, 79,
+        "0.0000000000000000099999998377515902426605765018763349871733225882053375244140625"},
+    {1e-16f, chars_format::fixed, 77,
+        "0.00000000000000010000000168623835263871646450439811815158464014530181884765625"},
+    {1e-15f, chars_format::fixed, 73, "0.0000000000000010000000036274937255387218471014421083964407444000244140625"},
+    {1e-14f, chars_format::fixed, 68, "0.00000000000000999999982451670044181213370393379591405391693115234375"},
+    {1e-13f, chars_format::fixed, 67, "0.0000000000000999999982451670044181213370393379591405391693115234375"},
+    {1e-12f, chars_format::fixed, 61, "0.0000000000009999999960041972002500187954865396022796630859375"},
+    {1e-11f, chars_format::fixed, 60, "0.000000000009999999960041972002500187954865396022796630859375"},
+    {1e-10f, chars_format::fixed, 57, "0.000000000100000001335143196001808973960578441619873046875"},
+    {1e-09f, chars_format::fixed, 53, "0.00000000099999997171806853657471947371959686279296875"},
+    {1e-08f, chars_format::fixed, 50, "0.00000000999999993922529029077850282192230224609375"},
+    {1e-07f, chars_format::fixed, 47, "0.00000010000000116860974230803549289703369140625"},
+    {1e-06f, chars_format::fixed, 43, "0.0000009999999974752427078783512115478515625"},
+    {1e-05f, chars_format::fixed, 38, "0.00000999999974737875163555145263671875"},
+    {1e-04f, chars_format::fixed, 37, "0.0000999999974737875163555145263671875"},
+    {1e-03f, chars_format::fixed, 33, "0.001000000047497451305389404296875"},
+    {1e-02f, chars_format::fixed, 29, "0.00999999977648258209228515625"},
+    {1e-01f, chars_format::fixed, 27, "0.100000001490116119384765625"},
+    {1e+00f, chars_format::fixed, 0, "1"},
+    {1e+01f, chars_format::fixed, 0, "10"},
+    {1e+02f, chars_format::fixed, 0, "100"},
+    {1e+03f, chars_format::fixed, 0, "1000"},
+    {1e+04f, chars_format::fixed, 0, "10000"},
+    {1e+05f, chars_format::fixed, 0, "100000"},
+    {1e+06f, chars_format::fixed, 0, "1000000"},
+    {1e+07f, chars_format::fixed, 0, "10000000"},
+    {1e+08f, chars_format::fixed, 0, "100000000"},
+    {1e+09f, chars_format::fixed, 0, "1000000000"},
+    {1e+10f, chars_format::fixed, 0, "10000000000"},
+    {1e+11f, chars_format::fixed, 0, "99999997952"},
+    {1e+12f, chars_format::fixed, 0, "999999995904"},
+    {1e+13f, chars_format::fixed, 0, "9999999827968"},
+    {1e+14f, chars_format::fixed, 0, "100000000376832"},
+    {1e+15f, chars_format::fixed, 0, "999999986991104"},
+    {1e+16f, chars_format::fixed, 0, "10000000272564224"},
+    {1e+17f, chars_format::fixed, 0, "99999998430674944"},
+    {1e+18f, chars_format::fixed, 0, "999999984306749440"},
+    {1e+19f, chars_format::fixed, 0, "9999999980506447872"},
+    {1e+20f, chars_format::fixed, 0, "100000002004087734272"},
+    {1e+21f, chars_format::fixed, 0, "1000000020040877342720"},
+    {1e+22f, chars_format::fixed, 0, "9999999778196308361216"},
+    {1e+23f, chars_format::fixed, 0, "99999997781963083612160"},
+    {1e+24f, chars_format::fixed, 0, "1000000013848427855085568"},
+    {1e+25f, chars_format::fixed, 0, "9999999562023526247432192"},
+    {1e+26f, chars_format::fixed, 0, "100000002537764290115403776"},
+    {1e+27f, chars_format::fixed, 0, "999999988484154753734934528"},
+    {1e+28f, chars_format::fixed, 0, "9999999442119689768320106496"},
+    {1e+29f, chars_format::fixed, 0, "100000001504746621987668885504"},
+    {1e+30f, chars_format::fixed, 0, "1000000015047466219876688855040"},
+    {1e+31f, chars_format::fixed, 0, "9999999848243207295109594873856"},
+    {1e+32f, chars_format::fixed, 0, "100000003318135351409612647563264"},
+    {1e+33f, chars_format::fixed, 0, "999999994495727286427992885035008"},
+    {1e+34f, chars_format::fixed, 0, "9999999790214767953607394487959552"},
+    {1e+35f, chars_format::fixed, 0, "100000004091847875962975319375216640"},
+    {1e+36f, chars_format::fixed, 0, "999999961690316245365415600208216064"},
+    {1e+37f, chars_format::fixed, 0, "9999999933815812510711506376257961984"},
+    {1e+38f, chars_format::fixed, 0, "99999996802856924650656260769173209088"},
+
+    // Ryu Printf RoundToEven
+    {0.125f, chars_format::fixed, 3, "0.125"},
+    {0.125f, chars_format::fixed, 2, "0.12"},
+    {0.375f, chars_format::fixed, 3, "0.375"},
+    {0.375f, chars_format::fixed, 2, "0.38"},
+
+    // Ryu Printf RoundToEvenInteger
+    {2.5f, chars_format::fixed, 1, "2.5"},
+    {2.5f, chars_format::fixed, 0, "2"},
+    {3.5f, chars_format::fixed, 1, "3.5"},
+    {3.5f, chars_format::fixed, 0, "4"},
+
+    // Ryu Printf NonRoundToEvenScenarios
+    {0.748046875f, chars_format::fixed, 3, "0.748"},
+    {0.748046875f, chars_format::fixed, 2, "0.75"},
+    {0.748046875f, chars_format::fixed, 1, "0.7"}, // 0.75 would round to "0.8", but this is smaller
+
+    {0.2509765625f, chars_format::fixed, 3, "0.251"},
+    {0.2509765625f, chars_format::fixed, 2, "0.25"},
+    {0.2509765625f, chars_format::fixed, 1, "0.3"}, // 0.25 would round to "0.2", but this is larger
+
+    {0x1.000002p-2f, chars_format::fixed, 25, "0.2500000298023223876953125"},
+    {0x1.000002p-2f, chars_format::fixed, 3, "0.250"},
+    {0x1.000002p-2f, chars_format::fixed, 2, "0.25"},
+    {0x1.000002p-2f, chars_format::fixed, 1, "0.3"}, // 0.25 would round to "0.2", but this is larger (again)
+
+    // More rounding tests.
+    {9.5f, chars_format::fixed, 1, "9.5"},
+    {9.5f, chars_format::fixed, 0, "10"},
+    {10.5f, chars_format::fixed, 1, "10.5"},
+    {10.5f, chars_format::fixed, 0, "10"},
+
+    {1.241f, chars_format::fixed, 3, "1.241"},
+    {1.241f, chars_format::fixed, 1, "1.2"},
+    {1.251f, chars_format::fixed, 3, "1.251"},
+    {1.251f, chars_format::fixed, 1, "1.3"},
+    {1.261f, chars_format::fixed, 3, "1.261"},
+    {1.261f, chars_format::fixed, 1, "1.3"},
+    {1.341f, chars_format::fixed, 3, "1.341"},
+    {1.341f, chars_format::fixed, 1, "1.3"},
+    {1.351f, chars_format::fixed, 3, "1.351"},
+    {1.351f, chars_format::fixed, 1, "1.4"},
+    {1.361f, chars_format::fixed, 3, "1.361"},
+    {1.361f, chars_format::fixed, 1, "1.4"},
+
+    {2.41f, chars_format::fixed, 2, "2.41"},
+    {2.41f, chars_format::fixed, 0, "2"},
+    {2.51f, chars_format::fixed, 2, "2.51"},
+    {2.51f, chars_format::fixed, 0, "3"},
+    {2.61f, chars_format::fixed, 2, "2.61"},
+    {2.61f, chars_format::fixed, 0, "3"},
+    {3.41f, chars_format::fixed, 2, "3.41"},
+    {3.41f, chars_format::fixed, 0, "3"},
+    {3.51f, chars_format::fixed, 2, "3.51"},
+    {3.51f, chars_format::fixed, 0, "4"},
+    {3.61f, chars_format::fixed, 2, "3.61"},
+    {3.61f, chars_format::fixed, 0, "4"},
+
+    // Ryu Printf VaryingPrecision
+    {1.142857f, chars_format::fixed, 28, "1.1428569555282592773437500000"},
+    {1.142857f, chars_format::fixed, 27, "1.142856955528259277343750000"},
+    {1.142857f, chars_format::fixed, 26, "1.14285695552825927734375000"},
+    {1.142857f, chars_format::fixed, 25, "1.1428569555282592773437500"},
+    {1.142857f, chars_format::fixed, 24, "1.142856955528259277343750"},
+    {1.142857f, chars_format::fixed, 23, "1.14285695552825927734375"},
+    {1.142857f, chars_format::fixed, 22, "1.1428569555282592773438"},
+    {1.142857f, chars_format::fixed, 21, "1.142856955528259277344"},
+    {1.142857f, chars_format::fixed, 20, "1.14285695552825927734"},
+    {1.142857f, chars_format::fixed, 19, "1.1428569555282592773"},
+    {1.142857f, chars_format::fixed, 18, "1.142856955528259277"},
+    {1.142857f, chars_format::fixed, 17, "1.14285695552825928"},
+    {1.142857f, chars_format::fixed, 16, "1.1428569555282593"},
+    {1.142857f, chars_format::fixed, 15, "1.142856955528259"},
+    {1.142857f, chars_format::fixed, 14, "1.14285695552826"},
+    {1.142857f, chars_format::fixed, 13, "1.1428569555283"},
+    {1.142857f, chars_format::fixed, 12, "1.142856955528"},
+    {1.142857f, chars_format::fixed, 11, "1.14285695553"},
+    {1.142857f, chars_format::fixed, 10, "1.1428569555"},
+    {1.142857f, chars_format::fixed, 9, "1.142856956"},
+    {1.142857f, chars_format::fixed, 8, "1.14285696"},
+    {1.142857f, chars_format::fixed, 7, "1.1428570"},
+    {1.142857f, chars_format::fixed, 6, "1.142857"},
+    {1.142857f, chars_format::fixed, 5, "1.14286"},
+    {1.142857f, chars_format::fixed, 4, "1.1429"},
+    {1.142857f, chars_format::fixed, 3, "1.143"},
+    {1.142857f, chars_format::fixed, 2, "1.14"},
+    {1.142857f, chars_format::fixed, 1, "1.1"},
+    {1.142857f, chars_format::fixed, 0, "1"},
+
+    // Negative precision requests 6 digits of precision.
+    {1.142857f, chars_format::fixed, -1, "1.142857"},
+    {1.142857f, chars_format::fixed, -2, "1.142857"},
+    {1.142857f, chars_format::fixed, -3, "1.142857"},
+
+    // Ryu Printf Carrying
+    {0.0009f, chars_format::fixed, 4, "0.0009"},
+    {0.0009f, chars_format::fixed, 3, "0.001"},
+    {0.0029f, chars_format::fixed, 4, "0.0029"},
+    {0.0029f, chars_format::fixed, 3, "0.003"},
+    {0.0099f, chars_format::fixed, 4, "0.0099"},
+    {0.0099f, chars_format::fixed, 3, "0.010"},
+    {0.0299f, chars_format::fixed, 4, "0.0299"},
+    {0.0299f, chars_format::fixed, 3, "0.030"},
+    {0.0999f, chars_format::fixed, 4, "0.0999"},
+    {0.0999f, chars_format::fixed, 3, "0.100"},
+    {0.2999f, chars_format::fixed, 4, "0.2999"},
+    {0.2999f, chars_format::fixed, 3, "0.300"},
+    {0.9999f, chars_format::fixed, 4, "0.9999"},
+    {0.9999f, chars_format::fixed, 3, "1.000"},
+    {2.9999f, chars_format::fixed, 4, "2.9999"},
+    {2.9999f, chars_format::fixed, 3, "3.000"},
+    {9.9999f, chars_format::fixed, 4, "9.9999"},
+    {9.9999f, chars_format::fixed, 3, "10.000"},
+    {29.9999f, chars_format::fixed, 4, "29.9999"},
+    {29.9999f, chars_format::fixed, 3, "30.000"},
+    {99.9999f, chars_format::fixed, 4, "99.9999"},
+    {99.9999f, chars_format::fixed, 3, "100.000"},
+    {299.9999f, chars_format::fixed, 4, "299.9999"},
+    {299.9999f, chars_format::fixed, 3, "300.000"},
+
+    {0.09f, chars_format::fixed, 2, "0.09"},
+    {0.09f, chars_format::fixed, 1, "0.1"},
+    {0.29f, chars_format::fixed, 2, "0.29"},
+    {0.29f, chars_format::fixed, 1, "0.3"},
+    {0.99f, chars_format::fixed, 2, "0.99"},
+    {0.99f, chars_format::fixed, 1, "1.0"},
+    {2.99f, chars_format::fixed, 2, "2.99"},
+    {2.99f, chars_format::fixed, 1, "3.0"},
+    {9.99f, chars_format::fixed, 2, "9.99"},
+    {9.99f, chars_format::fixed, 1, "10.0"},
+    {29.99f, chars_format::fixed, 2, "29.99"},
+    {29.99f, chars_format::fixed, 1, "30.0"},
+    {99.99f, chars_format::fixed, 2, "99.99"},
+    {99.99f, chars_format::fixed, 1, "100.0"},
+    {299.99f, chars_format::fixed, 2, "299.99"},
+    {299.99f, chars_format::fixed, 1, "300.0"},
+
+    {0.9f, chars_format::fixed, 1, "0.9"},
+    {0.9f, chars_format::fixed, 0, "1"},
+    {2.9f, chars_format::fixed, 1, "2.9"},
+    {2.9f, chars_format::fixed, 0, "3"},
+    {9.9f, chars_format::fixed, 1, "9.9"},
+    {9.9f, chars_format::fixed, 0, "10"},
+    {29.9f, chars_format::fixed, 1, "29.9"},
+    {29.9f, chars_format::fixed, 0, "30"},
+    {99.9f, chars_format::fixed, 1, "99.9"},
+    {99.9f, chars_format::fixed, 0, "100"},
+    {299.9f, chars_format::fixed, 1, "299.9"},
+    {299.9f, chars_format::fixed, 0, "300"},
+
+    // Ryu Printf RoundingResultZero
+    {0.004f, chars_format::fixed, 3, "0.004"},
+    {0.004f, chars_format::fixed, 2, "0.00"},
+    {0.4f, chars_format::fixed, 1, "0.4"},
+    {0.4f, chars_format::fixed, 0, "0"},
+    {0.5f, chars_format::fixed, 1, "0.5"},
+    {0.5f, chars_format::fixed, 0, "0"},
+
+    // Ryu Printf AllBinaryExponents
+    // These values test every binary exponent.
+    // The mantissas were randomly generated.
+    {0x0.bafab0p-126f, chars_format::fixed, 146,
+        "0."
+        "0000000000000000000000000000000000000085856660078164374052571520381239855817217629811131320365461649230225"
+        "8101698697601023013703525066375732421875"},
+    {0x1.2c4906p-126f, chars_format::fixed, 149,
+        "0."
+        "0000000000000000000000000000000000000137884223604447257991705553959882023830165636017936204355992973751997"
+        "2013648494879589634365402162075042724609375"},
+    {0x1.da6c8cp-125f, chars_format::fixed, 147,
+        "0."
+        "0000000000000000000000000000000000000435689644606144922962341034916717454461784748180572306511365470365953"
+        "68653788540314053534530103206634521484375"},
+    {0x1.094fd8p-124f, chars_format::fixed, 145,
+        "0."
+        "0000000000000000000000000000000000000487300980449569406486898593097235018686258578182781609022211792895361"
+        "293087574949822737835347652435302734375"},
+    {0x1.1fba2ap-123f, chars_format::fixed, 146,
+        "0."
+        "0000000000000000000000000000000000001056942819182250793988103906000418825212997860175004035399177620979400"
+        "2661102041429330711252987384796142578125"},
+    {0x1.05c066p-122f, chars_format::fixed, 145,
+        "0."
+        "0000000000000000000000000000000000001923046724143804860574903666495417184272104431219282642086921032167044"
+        "776084452450959361158311367034912109375"},
+    {0x1.aa97aep-121f, chars_format::fixed, 144,
+        "0."
+        "0000000000000000000000000000000000006268213405227838203431757007863521825324812101203856469220875149766722"
+        "40063493291017948649823665618896484375"},
+    {0x1.dd39a8p-120f, chars_format::fixed, 141,
+        "0."
+        "0000000000000000000000000000000000014024388746462477508516570165943074639858849697711014853285027082288594"
+        "08023936339304782450199127197265625"},
+    {0x1.d47ee4p-119f, chars_format::fixed, 141,
+        "0."
+        "0000000000000000000000000000000000027535700468003209195416842287342046227746219166975594715835834154840644"
+        "49429979504202492535114288330078125"},
+    {0x1.3d3c36p-118f, chars_format::fixed, 141,
+        "0."
+        "0000000000000000000000000000000000037290818427663765497432907740725131368928567215367442737882934305701509"
+        "99159295679419301450252532958984375"},
+    {0x1.1661f4p-117f, chars_format::fixed, 139,
+        "0."
+        "0000000000000000000000000000000000065447441644065192772010189083715139205202243608571574700187600294454259"
+        "852727773250080645084381103515625"},
+    {0x1.b68df4p-116f, chars_format::fixed, 138,
+        "0."
+        "0000000000000000000000000000000000206207336977375818320192367186588031181149116107584831794039036470533865"
+        "49714559805579483509063720703125"},
+    {0x1.d99cbcp-115f, chars_format::fixed, 137,
+        "0."
+        "0000000000000000000000000000000000445382813514879099167344241437088992337862296399353856123689687079858501"
+        "3062620419077575206756591796875"},
+    {0x1.fd046ep-114f, chars_format::fixed, 137,
+        "0."
+        "0000000000000000000000000000000000957355143513621934625335631305232671680527244248210039119495722709229923"
+        "4527672524563968181610107421875"},
+    {0x1.89834cp-113f, chars_format::fixed, 135,
+        "0."
+        "0000000000000000000000000000000001480230929779647770398330978023641189899501899250006144284413575618053471"
+        "31667076610028743743896484375"},
+    {0x1.44f9f6p-112f, chars_format::fixed, 135,
+        "0."
+        "0000000000000000000000000000000002444850777614032698558632186222413041911856813461843446368257012912827974"
+        "56005937419831752777099609375"},
+    {0x1.610156p-111f, chars_format::fixed, 134,
+        "0."
+        "0000000000000000000000000000000005311432194104638958491823018983379637847618995394862767718806989547530861"
+        "2731168977916240692138671875"},
+    {0x1.1c4ce0p-110f, chars_format::fixed, 129,
+        "0."
+        "0000000000000000000000000000000008555350741040305433153411782350510989661057055423470539198826934068620175"
+        "82170665264129638671875"},
+    {0x1.c8846ap-109f, chars_format::fixed, 132,
+        "0."
+        "0000000000000000000000000000000027475632104005746766942313987412370292282555616009485081234833825369889837"
+        "02030964195728302001953125"},
+    {0x1.49aaa6p-108f, chars_format::fixed, 131,
+        "0."
+        "0000000000000000000000000000000039682172991165697309827799919973022713504068615668209476284727932338114442"
+        "2455690801143646240234375"},
+    {0x1.f5603cp-107f, chars_format::fixed, 129,
+        "0."
+        "0000000000000000000000000000000120701861138584576157150361758540470962569680234040676814963322094342856871"
+        "66266143321990966796875"},
+    {0x1.b7bbf8p-106f, chars_format::fixed, 127,
+        "0."
+        "0000000000000000000000000000000211724341322508937840915176712265363597160619557838059749677039889093066449"
+        "277102947235107421875"},
+    {0x1.6d305cp-105f, chars_format::fixed, 127,
+        "0."
+        "0000000000000000000000000000000351664122601460292174574136500884378151845989294218826175242309517443572985"
+        "939681529998779296875"},
+    {0x1.dd9944p-104f, chars_format::fixed, 126,
+        "0."
+        "0000000000000000000000000000000919821625881433083724268012282371631728046815243377909779298740033937065163"
+        "62726688385009765625"},
+    {0x1.0f4254p-103f, chars_format::fixed, 125,
+        "0."
+        "0000000000000000000000000000001044852024561729954450605502201132293228119140390439904125807757395705266389"
+        "9958133697509765625"},
+    {0x1.049450p-102f, chars_format::fixed, 122,
+        "0."
+        "0000000000000000000000000000002007430259113927348388472759172849833669167623529955984951200775867619086056"
+        "9477081298828125"},
+    {0x1.28d030p-101f, chars_format::fixed, 121,
+        "0."
+        "0000000000000000000000000000004573131937693259427041496124538667251427229422876784281637441154089174233376"
+        "979827880859375"},
+    {0x1.28a2bep-100f, chars_format::fixed, 123,
+        "0."
+        "0000000000000000000000000000009140793594875532256935908936727717060368161903718573976784789181238011224195"
+        "36113739013671875"},
+    {0x1.e674d2p-99f, chars_format::fixed, 122,
+        "0."
+        "0000000000000000000000000000029980185962354845050897219390986524441297232842758378051906120731473492924124"
+        "0024566650390625"},
+    {0x1.227314p-98f, chars_format::fixed, 120,
+        "0."
+        "0000000000000000000000000000035800667869547456776694564979794758804336827210561614021067100566142471507191"
+        "65802001953125"},
+    {0x1.735b6cp-97f, chars_format::fixed, 119,
+        "0."
+        "0000000000000000000000000000091546597262378319603799081529207906703837108826262575211885064163652714341878"
+        "8909912109375"},
+    {0x1.ef60b4p-96f, chars_format::fixed, 118,
+        "0."
+        "0000000000000000000000000000244240085996903849216356078751341022854748745722804070812372856380534358322620"
+        "391845703125"},
+    {0x1.f58d34p-95f, chars_format::fixed, 117,
+        "0."
+        "0000000000000000000000000000494568036548015750964222103779193000963396430755616983709899159293854609131813"
+        "04931640625"},
+    {0x1.a9fa8ap-94f, chars_format::fixed, 117,
+        "0."
+        "0000000000000000000000000000840094794528154864080325730507983995095850536733231295194457288744160905480384"
+        "82666015625"},
+    {0x1.2ebd9ap-93f, chars_format::fixed, 116,
+        "0."
+        "0000000000000000000000000001194101241497498690354073604120044306874891791320908440710013564967084676027297"
+        "9736328125"},
+    {0x1.1c25bep-92f, chars_format::fixed, 115,
+        "0."
+        "0000000000000000000000000002241527991772840369420073304083191365256388471842441401093992681126110255718231"
+        "201171875"},
+    {0x1.80d526p-91f, chars_format::fixed, 114,
+        "0."
+        "0000000000000000000000000006071588038765549904506806942923684386898144178454361785668425000039860606193542"
+        "48046875"},
+    {0x1.16cdd0p-90f, chars_format::fixed, 110,
+        "0."
+        "0000000000000000000000000008797501615285119946834874987404311536605839433322628906353202182799577713012695"
+        "3125"},
+    {0x1.be00c0p-89f, chars_format::fixed, 107,
+        "0."
+        "0000000000000000000000000028146741987560362391732368583172300827762585262448169487470295280218124389648437"
+        "5"},
+    {0x1.dbe376p-88f, chars_format::fixed, 111,
+        "0."
+        "0000000000000000000000000060065575697458565955014820557088473772922162727261330417150020366534590721130371"
+        "09375"},
+    {0x1.75b358p-87f, chars_format::fixed, 108,
+        "0."
+        "0000000000000000000000000094335284238393382638914933670753282739891362740358715655020205304026603698730468"
+        "75"},
+    {0x1.5e56fap-86f, chars_format::fixed, 109,
+        "0."
+        "0000000000000000000000000176876373794073549186243776242822499413496518949617808402763330377638339996337890"
+        "625"},
+    {0x1.1542e6p-85f, chars_format::fixed, 108,
+        "0."
+        "0000000000000000000000000279962390364982552136537973532622361314990341862873890477203531190752983093261718"
+        "75"},
+    {0x1.37b7a6p-84f, chars_format::fixed, 107,
+        "0."
+        "0000000000000000000000000629508229027247503098930994487426088983880040350626927647681441158056259155273437"
+        "5"},
+    {0x1.31f62ap-83f, chars_format::fixed, 106,
+        "0."
+        "000000000000000000000000123576897369666466985856753932114511864998745993560191891447175294160842895507812"
+        "5"},
+    {0x1.ac3560p-82f, chars_format::fixed, 101,
+        "0.00000000000000000000000034590406845628797200186450581230516131137076030199750675819814205169677734375"},
+    {0x1.a7db5cp-81f, chars_format::fixed, 103,
+        "0."
+        "0000000000000000000000006847777099176331341674240101847394713956151957034990118700079619884490966796875"},
+    {0x1.40189cp-80f, chars_format::fixed, 102,
+        "0.000000000000000000000001034286379672715366987641733210033664035198963659922810620628297328948974609375"},
+    {0x1.aad1eep-79f, chars_format::fixed, 102,
+        "0.000000000000000000000002758259846499093682487211692864773559218105614121441249153576791286468505859375"},
+    {0x1.49824cp-78f, chars_format::fixed, 100,
+        "0.0000000000000000000000042588036474940459085811637121780459484809977510622047702781856060028076171875"},
+    {0x1.955292p-77f, chars_format::fixed, 100,
+        "0.0000000000000000000000104773420985315373838626628182169411331037256474019159213639795780181884765625"},
+    {0x1.d8ca0cp-76f, chars_format::fixed, 98,
+        "0.00000000000000000000002444263111177596802332967266437459101513507420122550684027373790740966796875"},
+    {0x1.28b5aap-75f, chars_format::fixed, 98,
+        "0.00000000000000000000003067905619497844072028707730390270809472941238027487997896969318389892578125"},
+    {0x1.e5fda8p-74f, chars_format::fixed, 95,
+        "0.00000000000000000000010050055115902033206854316793794380802129495577901252545416355133056640625"},
+    {0x1.fd929cp-73f, chars_format::fixed, 95,
+        "0.00000000000000000000021075432611470358337541921610390309449467594049565377645194530487060546875"},
+    {0x1.c0b84cp-72f, chars_format::fixed, 94,
+        "0.0000000000000000000003711724097438896357340602997067040280665395357573288492858409881591796875"},
+    {0x1.5cfeaep-71f, chars_format::fixed, 94,
+        "0.0000000000000000000005773635352424624465965559338086719731730767080080113373696804046630859375"},
+    {0x1.bcce4ap-70f, chars_format::fixed, 93,
+        "0.000000000000000000001471738991536079335112024613790339400143380998997599817812442779541015625"},
+    {0x1.edf106p-69f, chars_format::fixed, 92,
+        "0.00000000000000000000326863064574260634910627773444362353938430487687583081424236297607421875"},
+    {0x1.30b422p-68f, chars_format::fixed, 91,
+        "0.0000000000000000000040327191475944672156035895296995186232180685692583210766315460205078125"},
+    {0x1.7aa8d8p-67f, chars_format::fixed, 88,
+        "0.0000000000000000000100230347240102665385544432156972316505516573670320212841033935546875"},
+    {0x1.4ad4e0p-66f, chars_format::fixed, 85,
+        "0.0000000000000000000175140760553442509348562143578487138029231573455035686492919921875"},
+    {0x1.dde636p-65f, chars_format::fixed, 88,
+        "0.0000000000000000000505995524921864861016965251964971894693690046551637351512908935546875"},
+    {0x1.5df870p-64f, chars_format::fixed, 84,
+        "0.000000000000000000074109127331368847396687003781234892585416673682630062103271484375"},
+    {0x1.c346fap-63f, chars_format::fixed, 86,
+        "0.00000000000000000019112335047873604296656620434025075638828639057464897632598876953125"},
+    {0x1.58d2eap-62f, chars_format::fixed, 85,
+        "0.0000000000000000002920771899491385068938311721231659845443573431111872196197509765625"},
+    {0x1.0d4824p-61f, chars_format::fixed, 83,
+        "0.00000000000000000045618111223383324851561766710705825289551285095512866973876953125"},
+    {0x1.04585cp-60f, chars_format::fixed, 82,
+        "0.0000000000000000008820836917354691955064048547452415505176759324967861175537109375"},
+    {0x1.55cf7ap-59f, chars_format::fixed, 82,
+        "0.0000000000000000023161977389916240139687737820128887733517331071197986602783203125"},
+    {0x1.1fd8ecp-58f, chars_format::fixed, 80,
+        "0.00000000000000000390105904223582084021197668999292318403604440391063690185546875"},
+    {0x1.0bc866p-57f, chars_format::fixed, 80,
+        "0.00000000000000000725826751123333980988787395016714754092390649020671844482421875"},
+    {0x1.4dfa86p-56f, chars_format::fixed, 79,
+        "0.0000000000000000181050165732891247031242920595417444928898476064205169677734375"},
+    {0x1.335daep-55f, chars_format::fixed, 78,
+        "0.000000000000000033324681586205479543426333233213654239079914987087249755859375"},
+    {0x1.5bc756p-54f, chars_format::fixed, 77,
+        "0.00000000000000007541247487712833172911197632259927559061907231807708740234375"},
+    {0x1.9eb052p-53f, chars_format::fixed, 76,
+        "0.0000000000000001798425779915148827771409489884035792783834040164947509765625"},
+    {0x1.13b6d2p-52f, chars_format::fixed, 75,
+        "0.000000000000000239143897259270284301468922905087310937233269214630126953125"},
+    {0x1.260438p-51f, chars_format::fixed, 72,
+        "0.000000000000000510037289299151118393549353413618518970906734466552734375"},
+    {0x1.9e6b44p-50f, chars_format::fixed, 72,
+        "0.000000000000001437804758404521467129999479084290214814245700836181640625"},
+    {0x1.89c0bcp-49f, chars_format::fixed, 71,
+        "0.00000000000000273220937993773164975674916377101908437907695770263671875"},
+    {0x1.e30610p-48f, chars_format::fixed, 68,
+        "0.00000000000000670330015995791728133923470522859133780002593994140625"},
+    {0x1.48b6e8p-47f, chars_format::fixed, 68,
+        "0.00000000000000912365953728740131101204724473063834011554718017578125"},
+    {0x1.41382ep-46f, chars_format::fixed, 69,
+        "0.000000000000017831261573081173821275768887062440626323223114013671875"},
+    {0x1.383b8ep-45f, chars_format::fixed, 68,
+        "0.00000000000003466478609693256218715617933412431739270687103271484375"},
+    {0x1.1e6564p-44f, chars_format::fixed, 66, "0.000000000000063592699357274684590635160930105485022068023681640625"},
+    {0x1.c35e62p-43f, chars_format::fixed, 66, "0.000000000000200447961722950707130763703389675356447696685791015625"},
+    {0x1.2a2f4ep-42f, chars_format::fixed, 65, "0.00000000000026484129017449731247069166784058324992656707763671875"},
+    {0x1.69fae2p-41f, chars_format::fixed, 64, "0.0000000000006430056682417417679431537180789746344089508056640625"},
+    {0x1.4ccefep-40f, chars_format::fixed, 63, "0.000000000001182373535017766652543969030375592410564422607421875"},
+    {0x1.aa9bf6p-39f, chars_format::fixed, 62, "0.00000000000303124083993189241681420753593556582927703857421875"},
+    {0x1.3b9744p-38f, chars_format::fixed, 60, "0.000000000004484816164274096905728583806194365024566650390625"},
+    {0x1.b2fc6ap-37f, chars_format::fixed, 60, "0.000000000012363045483188006556929394719190895557403564453125"},
+    {0x1.7bc418p-36f, chars_format::fixed, 57, "0.000000000021587197307493255493682227097451686859130859375"},
+    {0x1.f4a74cp-35f, chars_format::fixed, 57, "0.000000000056917713597837149563929415307939052581787109375"},
+    {0x1.89f248p-34f, chars_format::fixed, 55, "0.0000000000895730434269381703416001982986927032470703125"},
+    {0x1.60ac54p-33f, chars_format::fixed, 55, "0.0000000001603771837555001411601551808416843414306640625"},
+    {0x1.2f6d0ep-32f, chars_format::fixed, 55, "0.0000000002759643347172158200919511727988719940185546875"},
+    {0x1.748684p-31f, chars_format::fixed, 53, "0.00000000067761984912095840627443976700305938720703125"},
+    {0x1.b4fa00p-30f, chars_format::fixed, 45, "0.000000001589711473570787347853183746337890625"},
+    {0x1.c204d8p-29f, chars_format::fixed, 50, "0.00000000327431859403759517590515315532684326171875"},
+    {0x1.50029ep-28f, chars_format::fixed, 51, "0.000000004889592286616561978007666766643524169921875"},
+    {0x1.56cf38p-27f, chars_format::fixed, 48, "0.000000009977068060607052757404744625091552734375"},
+    {0x1.0b5a5cp-26f, chars_format::fixed, 48, "0.000000015561990807100301026366651058197021484375"},
+    {0x1.fc8250p-25f, chars_format::fixed, 45, "0.000000059198242752245278097689151763916015625"},
+    {0x1.c66674p-24f, chars_format::fixed, 46, "0.0000001057982927932243910618126392364501953125"},
+    {0x1.4da57ep-23f, chars_format::fixed, 46, "0.0000001553662372089092968963086605072021484375"},
+    {0x1.4fcdacp-22f, chars_format::fixed, 44, "0.00000031274129241865011863410472869873046875"},
+    {0x1.5eaff4p-21f, chars_format::fixed, 43, "0.0000006532060297104180790483951568603515625"},
+    {0x1.d2f696p-20f, chars_format::fixed, 43, "0.0000017395735767422593198716640472412109375"},
+    {0x1.e4400cp-19f, chars_format::fixed, 41, "0.00000360794501830241642892360687255859375"},
+    {0x1.03e624p-18f, chars_format::fixed, 40, "0.0000038727966966689564287662506103515625"},
+    {0x1.bdb65ep-17f, chars_format::fixed, 40, "0.0000132832637973478995263576507568359375"},
+    {0x1.57fb84p-16f, chars_format::fixed, 38, "0.00002050295370281673967838287353515625"},
+    {0x1.fd2d62p-15f, chars_format::fixed, 38, "0.00006069866140023805201053619384765625"},
+    {0x1.ca0c58p-14f, chars_format::fixed, 35, "0.00010920720524154603481292724609375"},
+    {0x1.988f70p-13f, chars_format::fixed, 33, "0.000194816733710467815399169921875"},
+    {0x1.032dd6p-12f, chars_format::fixed, 35, "0.00024717240012250840663909912109375"},
+    {0x1.571b08p-11f, chars_format::fixed, 32, "0.00065442197956144809722900390625"},
+    {0x1.53bedap-10f, chars_format::fixed, 33, "0.001296026282943785190582275390625"},
+    {0x1.ab2f36p-9f, chars_format::fixed, 32, "0.00325915846042335033416748046875"},
+    {0x1.7293dap-8f, chars_format::fixed, 31, "0.0056545645929872989654541015625"},
+    {0x1.825eb6p-7f, chars_format::fixed, 30, "0.011791075579822063446044921875"},
+    {0x1.f45aa0p-6f, chars_format::fixed, 25, "0.0305391848087310791015625"},
+    {0x1.854d96p-5f, chars_format::fixed, 28, "0.0475223474204540252685546875"},
+    {0x1.5650cep-4f, chars_format::fixed, 27, "0.083573155105113983154296875"},
+    {0x1.03acdap-3f, chars_format::fixed, 26, "0.12679453194141387939453125"},
+    {0x1.6b9416p-2f, chars_format::fixed, 25, "0.3550570905208587646484375"},
+    {0x1.a8544ap-1f, chars_format::fixed, 24, "0.828768074512481689453125"},
+    {0x1.0693f6p+0f, chars_format::fixed, 23, "1.02569520473480224609375"},
+    {0x1.b9476ep+1f, chars_format::fixed, 22, "3.4474923610687255859375"},
+    {0x1.3cb752p+2f, chars_format::fixed, 21, "4.948688983917236328125"},
+    {0x1.bb8a64p+3f, chars_format::fixed, 19, "13.8606433868408203125"},
+    {0x1.1de906p+4f, chars_format::fixed, 19, "17.8693904876708984375"},
+    {0x1.d8e834p+5f, chars_format::fixed, 17, "59.11338043212890625"},
+    {0x1.27cd38p+6f, chars_format::fixed, 15, "73.950408935546875"},
+    {0x1.3cdcd6p+7f, chars_format::fixed, 16, "158.4313201904296875"},
+    {0x1.392656p+8f, chars_format::fixed, 15, "313.149749755859375"},
+    {0x1.c96aa8p+9f, chars_format::fixed, 12, "914.833251953125"},
+    {0x1.28b6b2p+10f, chars_format::fixed, 13, "1186.8546142578125"},
+    {0x1.786090p+11f, chars_format::fixed, 9, "3011.017578125"},
+    {0x1.79c6f6p+12f, chars_format::fixed, 11, "6044.43505859375"},
+    {0x1.ef1840p+13f, chars_format::fixed, 5, "15843.03125"},
+    {0x1.539fd0p+14f, chars_format::fixed, 6, "21735.953125"},
+    {0x1.b31804p+15f, chars_format::fixed, 7, "55692.0078125"},
+    {0x1.ad4a9cp+16f, chars_format::fixed, 6, "109898.609375"},
+    {0x1.4c43a6p+17f, chars_format::fixed, 6, "170119.296875"},
+    {0x1.5598c6p+18f, chars_format::fixed, 5, "349795.09375"},
+    {0x1.73695ep+19f, chars_format::fixed, 4, "760650.9375"},
+    {0x1.234f2ap+20f, chars_format::fixed, 3, "1193202.625"},
+    {0x1.0a4cc8p+21f, chars_format::fixed, 0, "2181529"},
+    {0x1.90abd2p+22f, chars_format::fixed, 1, "6564596.5"},
+    {0x1.62dde8p+23f, chars_format::fixed, 0, "11628276"},
+    {0x1.9e3a8cp+24f, chars_format::fixed, 0, "27146892"},
+    {0x1.53a3eap+25f, chars_format::fixed, 0, "44517332"},
+    {0x1.41a1cep+26f, chars_format::fixed, 0, "84313912"},
+    {0x1.8fdda4p+27f, chars_format::fixed, 0, "209644832"},
+    {0x1.d0322ap+28f, chars_format::fixed, 0, "486744736"},
+    {0x1.cdb764p+29f, chars_format::fixed, 0, "968289408"},
+    {0x1.7620d8p+30f, chars_format::fixed, 0, "1569207808"},
+    {0x1.c18df6p+31f, chars_format::fixed, 0, "3771136768"},
+    {0x1.240cf8p+32f, chars_format::fixed, 0, "4899796992"},
+    {0x1.81669ap+33f, chars_format::fixed, 0, "12931904512"},
+    {0x1.3be30cp+34f, chars_format::fixed, 0, "21198811136"},
+    {0x1.d1e6e4p+35f, chars_format::fixed, 0, "62532296704"},
+    {0x1.06b274p+36f, chars_format::fixed, 0, "70517211136"},
+    {0x1.a74284p+37f, chars_format::fixed, 0, "227235889152"},
+    {0x1.9fd3e6p+38f, chars_format::fixed, 0, "446491623424"},
+    {0x1.e2cec4p+39f, chars_format::fixed, 0, "1036821594112"},
+    {0x1.3d5d32p+40f, chars_format::fixed, 0, "1363068190720"},
+    {0x1.accccap+41f, chars_format::fixed, 0, "3683363586048"},
+    {0x1.a120ccp+42f, chars_format::fixed, 0, "7166206410752"},
+    {0x1.55a028p+43f, chars_format::fixed, 0, "11738166591488"},
+    {0x1.035296p+44f, chars_format::fixed, 0, "17820513468416"},
+    {0x1.22d1aap+45f, chars_format::fixed, 0, "39969859043328"},
+    {0x1.eb8eaep+46f, chars_format::fixed, 0, "135118253457408"},
+    {0x1.490d0ep+47f, chars_format::fixed, 0, "180897697497088"},
+    {0x1.9da088p+48f, chars_format::fixed, 0, "454787778740224"},
+    {0x1.e7fab4p+49f, chars_format::fixed, 0, "1073077848899584"},
+    {0x1.98a534p+50f, chars_format::fixed, 0, "1797241144606720"},
+    {0x1.93aeeap+51f, chars_format::fixed, 0, "3550835489374208"},
+    {0x1.3df680p+52f, chars_format::fixed, 0, "5593662327095296"},
+    {0x1.c763f6p+53f, chars_format::fixed, 0, "16022627827056640"},
+    {0x1.8b669ep+54f, chars_format::fixed, 0, "27823861147893760"},
+    {0x1.73e5b6p+55f, chars_format::fixed, 0, "52339893103230976"},
+    {0x1.a13d18p+56f, chars_format::fixed, 0, "117442238576852992"},
+    {0x1.a0797ep+57f, chars_format::fixed, 0, "234454344768946176"},
+    {0x1.c07a80p+58f, chars_format::fixed, 0, "504941918963105792"},
+    {0x1.729388p+59f, chars_format::fixed, 0, "834463629662224384"},
+    {0x1.edfb70p+60f, chars_format::fixed, 0, "2224697951572197376"},
+    {0x1.3d6782p+61f, chars_format::fixed, 0, "2858924021141995520"},
+    {0x1.b121e8p+62f, chars_format::fixed, 0, "7802620494837972992"},
+    {0x1.0efc5ap+63f, chars_format::fixed, 0, "9763290520209063936"},
+    {0x1.b7dba0p+64f, chars_format::fixed, 0, "31695102724410441728"},
+    {0x1.ec2306p+65f, chars_format::fixed, 0, "70924388975830368256"},
+    {0x1.2e2d28p+66f, chars_format::fixed, 0, "87096415015485308928"},
+    {0x1.e02208p+67f, chars_format::fixed, 0, "276777792668052750336"},
+    {0x1.402636p+68f, chars_format::fixed, 0, "369106968238077509632"},
+    {0x1.11f97cp+69f, chars_format::fixed, 0, "631742296991907971072"},
+    {0x1.74db2ap+70f, chars_format::fixed, 0, "1719495307615820316672"},
+    {0x1.94a32ap+71f, chars_format::fixed, 0, "3732120907777931476992"},
+    {0x1.c272dcp+72f, chars_format::fixed, 0, "8309311323384498356224"},
+    {0x1.36ca40p+73f, chars_format::fixed, 0, "11466128622488263852032"},
+    {0x1.5f6fbep+74f, chars_format::fixed, 0, "25931436172223350571008"},
+    {0x1.95ec4ep+75f, chars_format::fixed, 0, "59903671176748022628352"},
+    {0x1.6b3912p+76f, chars_format::fixed, 0, "107204487170660958732288"},
+    {0x1.10992ap+77f, chars_format::fixed, 0, "160913632700346331561984"},
+    {0x1.74a25ep+78f, chars_format::fixed, 0, "439928869395322133020672"},
+    {0x1.43f462p+79f, chars_format::fixed, 0, "764916220582548125777920"},
+    {0x1.f12ca2p+80f, chars_format::fixed, 0, "2347839472055691035803648"},
+    {0x1.2b7f18p+81f, chars_format::fixed, 0, "2828664088515283884441600"},
+    {0x1.a40704p+82f, chars_format::fixed, 0, "7934093352976572433301504"},
+    {0x1.35d5f8p+83f, chars_format::fixed, 0, "11705266159821935293235200"},
+    {0x1.c2c9d2p+84f, chars_format::fixed, 0, "34060605519118462894473216"},
+    {0x1.47bf20p+85f, chars_format::fixed, 0, "49527663163502775133798400"},
+    {0x1.60b728p+86f, chars_format::fixed, 0, "106601704860119390738186240"},
+    {0x1.3354c8p+87f, chars_format::fixed, 0, "185770297377533474371534848"},
+    {0x1.e9e512p+88f, chars_format::fixed, 0, "592246479757524141957185536"},
+    {0x1.c4b6cap+89f, chars_format::fixed, 0, "1094595334815995103451021312"},
+    {0x1.799cb8p+90f, chars_format::fixed, 0, "1826020469467809704300249088"},
+    {0x1.1afa36p+91f, chars_format::fixed, 0, "2736789351009782551090823168"},
+    {0x1.80c214p+92f, chars_format::fixed, 0, "7442304364233212615194574848"},
+    {0x1.657890p+93f, chars_format::fixed, 0, "13828987453168434783077793792"},
+    {0x1.5ce17cp+94f, chars_format::fixed, 0, "26993344325171312829134798848"},
+    {0x1.3f1e9ap+95f, chars_format::fixed, 0, "49381356576017938861904625664"},
+    {0x1.874612p+96f, chars_format::fixed, 0, "121093348650115637567232671744"},
+    {0x1.5f4d5ep+97f, chars_format::fixed, 0, "217445539275703670631001227264"},
+    {0x1.45b1bep+98f, chars_format::fixed, 0, "403190021246562727728269754368"},
+    {0x1.a570f4p+99f, chars_format::fixed, 0, "1043437928672039460753056464896"},
+    {0x1.f5106ep+100f, chars_format::fixed, 0, "2481149635102733266542145830912"},
+    {0x1.d84424p+101f, chars_format::fixed, 0, "4677097651091265616934539886592"},
+    {0x1.3d6c56p+102f, chars_format::fixed, 0, "6287213966425746785671183335424"},
+    {0x1.9d8cf0p+103f, chars_format::fixed, 0, "16382424580981433623378525159424"},
+    {0x1.e2e73ep+104f, chars_format::fixed, 0, "38259540322544957537972440268800"},
+    {0x1.2d6594p+105f, chars_format::fixed, 0, "47758227647613648865431576903680"},
+    {0x1.ce43bap+106f, chars_format::fixed, 0, "146497485749802409635393442938880"},
+    {0x1.b3ea00p+107f, chars_format::fixed, 0, "276293361488025452794185737306112"},
+    {0x1.03a052p+108f, chars_format::fixed, 0, "329115373194929392757058784198656"},
+    {0x1.6f59e0p+109f, chars_format::fixed, 0, "931345619455766569116232623063040"},
+    {0x1.05adacp+110f, chars_format::fixed, 0, "1326867152522435745601434087849984"},
+    {0x1.2cdef0p+111f, chars_format::fixed, 0, "3051192904788012466473218045116416"},
+    {0x1.e81552p+112f, chars_format::fixed, 0, "9899505055765620068271358482579456"},
+    {0x1.bfa8f4p+113f, chars_format::fixed, 0, "18159245876954178992833811110166528"},
+    {0x1.a14810p+114f, chars_format::fixed, 0, "33853896736735722962455354188759040"},
+    {0x1.f18b10p+115f, chars_format::fixed, 0, "80731001914916160681187088757948416"},
+    {0x1.8d6e30p+116f, chars_format::fixed, 0, "128973545052908058560090358153216000"},
+    {0x1.9480c2p+117f, chars_format::fixed, 0, "262537431192608192877759864086986752"},
+    {0x1.60975cp+118f, chars_format::fixed, 0, "457689606761340509948952337218273280"},
+    {0x1.ab1bb2p+119f, chars_format::fixed, 0, "1108836243133298765768030079592431616"},
+    {0x1.6a0c80p+120f, chars_format::fixed, 0, "1879864992909653247408339011818749952"},
+    {0x1.2cac2cp+121f, chars_format::fixed, 0, "3122362236102854007005843883842076672"},
+    {0x1.0baaf6p+122f, chars_format::fixed, 0, "5559243043957593079267046257728684032"},
+    {0x1.098282p+123f, chars_format::fixed, 0, "11028845443370647144636654644992409600"},
+    {0x1.122f8ap+124f, chars_format::fixed, 0, "22778456735621461875293910785310326784"},
+    {0x1.57f4c6p+125f, chars_format::fixed, 0, "57149517363101270672263900542030315520"},
+    {0x1.05e028p+126f, chars_format::fixed, 0, "87023098173139747570875357950241669120"},
+    {0x1.9d8424p+127f, chars_format::fixed, 0, "274828637805621292108186801756142829568"},
+
+    // Test the maximum mantissa, which generates the most digits for each exponent.
+    {0x0.fffffep-126f, chars_format::fixed, 149,
+        "0."
+        "0000000000000000000000000000000000000117549421069244107548702944484928734882705242874589333385717453057158"
+        "8870475618904265502351336181163787841796875"},
+    {0x1.fffffep-126f, chars_format::fixed, 149,
+        "0."
+        "0000000000000000000000000000000000000235098856151472858345576598207153302664571798551798085536592623685000"
+        "6129930346077117064851336181163787841796875"},
+    {0x1.fffffep-125f, chars_format::fixed, 148,
+        "0."
+        "0000000000000000000000000000000000000470197712302945716691153196414306605329143597103596171073185247370001"
+        "225986069215423412970267236232757568359375"},
+    {0x1.fffffep-124f, chars_format::fixed, 147,
+        "0."
+        "0000000000000000000000000000000000000940395424605891433382306392828613210658287194207192342146370494740002"
+        "45197213843084682594053447246551513671875"},
+    {0x1.fffffep-123f, chars_format::fixed, 146,
+        "0."
+        "0000000000000000000000000000000000001880790849211782866764612785657226421316574388414384684292740989480004"
+        "9039442768616936518810689449310302734375"},
+    {0x1.fffffep-122f, chars_format::fixed, 145,
+        "0."
+        "0000000000000000000000000000000000003761581698423565733529225571314452842633148776828769368585481978960009"
+        "807888553723387303762137889862060546875"},
+    {0x1.fffffep-121f, chars_format::fixed, 144,
+        "0."
+        "0000000000000000000000000000000000007523163396847131467058451142628905685266297553657538737170963957920019"
+        "61577710744677460752427577972412109375"},
+    {0x1.fffffep-120f, chars_format::fixed, 143,
+        "0."
+        "0000000000000000000000000000000000015046326793694262934116902285257811370532595107315077474341927915840039"
+        "2315542148935492150485515594482421875"},
+    {0x1.fffffep-119f, chars_format::fixed, 142,
+        "0."
+        "0000000000000000000000000000000000030092653587388525868233804570515622741065190214630154948683855831680078"
+        "463108429787098430097103118896484375"},
+    {0x1.fffffep-118f, chars_format::fixed, 141,
+        "0."
+        "0000000000000000000000000000000000060185307174777051736467609141031245482130380429260309897367711663360156"
+        "92621685957419686019420623779296875"},
+    {0x1.fffffep-117f, chars_format::fixed, 140,
+        "0."
+        "0000000000000000000000000000000000120370614349554103472935218282062490964260760858520619794735423326720313"
+        "8524337191483937203884124755859375"},
+    {0x1.fffffep-116f, chars_format::fixed, 139,
+        "0."
+        "0000000000000000000000000000000000240741228699108206945870436564124981928521521717041239589470846653440627"
+        "704867438296787440776824951171875"},
+    {0x1.fffffep-115f, chars_format::fixed, 138,
+        "0."
+        "0000000000000000000000000000000000481482457398216413891740873128249963857043043434082479178941693306881255"
+        "40973487659357488155364990234375"},
+    {0x1.fffffep-114f, chars_format::fixed, 137,
+        "0."
+        "0000000000000000000000000000000000962964914796432827783481746256499927714086086868164958357883386613762510"
+        "8194697531871497631072998046875"},
+    {0x1.fffffep-113f, chars_format::fixed, 136,
+        "0."
+        "0000000000000000000000000000000001925929829592865655566963492512999855428172173736329916715766773227525021"
+        "638939506374299526214599609375"},
+    {0x1.fffffep-112f, chars_format::fixed, 135,
+        "0."
+        "0000000000000000000000000000000003851859659185731311133926985025999710856344347472659833431533546455050043"
+        "27787901274859905242919921875"},
+    {0x1.fffffep-111f, chars_format::fixed, 134,
+        "0."
+        "0000000000000000000000000000000007703719318371462622267853970051999421712688694945319666863067092910100086"
+        "5557580254971981048583984375"},
+    {0x1.fffffep-110f, chars_format::fixed, 133,
+        "0."
+        "0000000000000000000000000000000015407438636742925244535707940103998843425377389890639333726134185820200173"
+        "111516050994396209716796875"},
+    {0x1.fffffep-109f, chars_format::fixed, 132,
+        "0."
+        "0000000000000000000000000000000030814877273485850489071415880207997686850754779781278667452268371640400346"
+        "22303210198879241943359375"},
+    {0x1.fffffep-108f, chars_format::fixed, 131,
+        "0."
+        "0000000000000000000000000000000061629754546971700978142831760415995373701509559562557334904536743280800692"
+        "4460642039775848388671875"},
+    {0x1.fffffep-107f, chars_format::fixed, 130,
+        "0."
+        "0000000000000000000000000000000123259509093943401956285663520831990747403019119125114669809073486561601384"
+        "892128407955169677734375"},
+    {0x1.fffffep-106f, chars_format::fixed, 129,
+        "0."
+        "0000000000000000000000000000000246519018187886803912571327041663981494806038238250229339618146973123202769"
+        "78425681591033935546875"},
+    {0x1.fffffep-105f, chars_format::fixed, 128,
+        "0."
+        "0000000000000000000000000000000493038036375773607825142654083327962989612076476500458679236293946246405539"
+        "5685136318206787109375"},
+    {0x1.fffffep-104f, chars_format::fixed, 127,
+        "0."
+        "0000000000000000000000000000000986076072751547215650285308166655925979224152953000917358472587892492811079"
+        "137027263641357421875"},
+    {0x1.fffffep-103f, chars_format::fixed, 126,
+        "0."
+        "0000000000000000000000000000001972152145503094431300570616333311851958448305906001834716945175784985622158"
+        "27405452728271484375"},
+    {0x1.fffffep-102f, chars_format::fixed, 125,
+        "0."
+        "0000000000000000000000000000003944304291006188862601141232666623703916896611812003669433890351569971244316"
+        "5481090545654296875"},
+    {0x1.fffffep-101f, chars_format::fixed, 124,
+        "0."
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+    {0x1.fffffep+65f, chars_format::fixed, 0, "73786971896791695360"},
+    {0x1.fffffep+66f, chars_format::fixed, 0, "147573943793583390720"},
+    {0x1.fffffep+67f, chars_format::fixed, 0, "295147887587166781440"},
+    {0x1.fffffep+68f, chars_format::fixed, 0, "590295775174333562880"},
+    {0x1.fffffep+69f, chars_format::fixed, 0, "1180591550348667125760"},
+    {0x1.fffffep+70f, chars_format::fixed, 0, "2361183100697334251520"},
+    {0x1.fffffep+71f, chars_format::fixed, 0, "4722366201394668503040"},
+    {0x1.fffffep+72f, chars_format::fixed, 0, "9444732402789337006080"},
+    {0x1.fffffep+73f, chars_format::fixed, 0, "18889464805578674012160"},
+    {0x1.fffffep+74f, chars_format::fixed, 0, "37778929611157348024320"},
+    {0x1.fffffep+75f, chars_format::fixed, 0, "75557859222314696048640"},
+    {0x1.fffffep+76f, chars_format::fixed, 0, "151115718444629392097280"},
+    {0x1.fffffep+77f, chars_format::fixed, 0, "302231436889258784194560"},
+    {0x1.fffffep+78f, chars_format::fixed, 0, "604462873778517568389120"},
+    {0x1.fffffep+79f, chars_format::fixed, 0, "1208925747557035136778240"},
+    {0x1.fffffep+80f, chars_format::fixed, 0, "2417851495114070273556480"},
+    {0x1.fffffep+81f, chars_format::fixed, 0, "4835702990228140547112960"},
+    {0x1.fffffep+82f, chars_format::fixed, 0, "9671405980456281094225920"},
+    {0x1.fffffep+83f, chars_format::fixed, 0, "19342811960912562188451840"},
+    {0x1.fffffep+84f, chars_format::fixed, 0, "38685623921825124376903680"},
+    {0x1.fffffep+85f, chars_format::fixed, 0, "77371247843650248753807360"},
+    {0x1.fffffep+86f, chars_format::fixed, 0, "154742495687300497507614720"},
+    {0x1.fffffep+87f, chars_format::fixed, 0, "309484991374600995015229440"},
+    {0x1.fffffep+88f, chars_format::fixed, 0, "618969982749201990030458880"},
+    {0x1.fffffep+89f, chars_format::fixed, 0, "1237939965498403980060917760"},
+    {0x1.fffffep+90f, chars_format::fixed, 0, "2475879930996807960121835520"},
+    {0x1.fffffep+91f, chars_format::fixed, 0, "4951759861993615920243671040"},
+    {0x1.fffffep+92f, chars_format::fixed, 0, "9903519723987231840487342080"},
+    {0x1.fffffep+93f, chars_format::fixed, 0, "19807039447974463680974684160"},
+    {0x1.fffffep+94f, chars_format::fixed, 0, "39614078895948927361949368320"},
+    {0x1.fffffep+95f, chars_format::fixed, 0, "79228157791897854723898736640"},
+    {0x1.fffffep+96f, chars_format::fixed, 0, "158456315583795709447797473280"},
+    {0x1.fffffep+97f, chars_format::fixed, 0, "316912631167591418895594946560"},
+    {0x1.fffffep+98f, chars_format::fixed, 0, "633825262335182837791189893120"},
+    {0x1.fffffep+99f, chars_format::fixed, 0, "1267650524670365675582379786240"},
+    {0x1.fffffep+100f, chars_format::fixed, 0, "2535301049340731351164759572480"},
+    {0x1.fffffep+101f, chars_format::fixed, 0, "5070602098681462702329519144960"},
+    {0x1.fffffep+102f, chars_format::fixed, 0, "10141204197362925404659038289920"},
+    {0x1.fffffep+103f, chars_format::fixed, 0, "20282408394725850809318076579840"},
+    {0x1.fffffep+104f, chars_format::fixed, 0, "40564816789451701618636153159680"},
+    {0x1.fffffep+105f, chars_format::fixed, 0, "81129633578903403237272306319360"},
+    {0x1.fffffep+106f, chars_format::fixed, 0, "162259267157806806474544612638720"},
+    {0x1.fffffep+107f, chars_format::fixed, 0, "324518534315613612949089225277440"},
+    {0x1.fffffep+108f, chars_format::fixed, 0, "649037068631227225898178450554880"},
+    {0x1.fffffep+109f, chars_format::fixed, 0, "1298074137262454451796356901109760"},
+    {0x1.fffffep+110f, chars_format::fixed, 0, "2596148274524908903592713802219520"},
+    {0x1.fffffep+111f, chars_format::fixed, 0, "5192296549049817807185427604439040"},
+    {0x1.fffffep+112f, chars_format::fixed, 0, "10384593098099635614370855208878080"},
+    {0x1.fffffep+113f, chars_format::fixed, 0, "20769186196199271228741710417756160"},
+    {0x1.fffffep+114f, chars_format::fixed, 0, "41538372392398542457483420835512320"},
+    {0x1.fffffep+115f, chars_format::fixed, 0, "83076744784797084914966841671024640"},
+    {0x1.fffffep+116f, chars_format::fixed, 0, "166153489569594169829933683342049280"},
+    {0x1.fffffep+117f, chars_format::fixed, 0, "332306979139188339659867366684098560"},
+    {0x1.fffffep+118f, chars_format::fixed, 0, "664613958278376679319734733368197120"},
+    {0x1.fffffep+119f, chars_format::fixed, 0, "1329227916556753358639469466736394240"},
+    {0x1.fffffep+120f, chars_format::fixed, 0, "2658455833113506717278938933472788480"},
+    {0x1.fffffep+121f, chars_format::fixed, 0, "5316911666227013434557877866945576960"},
+    {0x1.fffffep+122f, chars_format::fixed, 0, "10633823332454026869115755733891153920"},
+    {0x1.fffffep+123f, chars_format::fixed, 0, "21267646664908053738231511467782307840"},
+    {0x1.fffffep+124f, chars_format::fixed, 0, "42535293329816107476463022935564615680"},
+    {0x1.fffffep+125f, chars_format::fixed, 0, "85070586659632214952926045871129231360"},
+    {0x1.fffffep+126f, chars_format::fixed, 0, "170141173319264429905852091742258462720"},
+    {0x1.fffffep+127f, chars_format::fixed, 0, "340282346638528859811704183484516925440"},
+};
+
+#endif // FLOAT_FIXED_PRECISION_TO_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/float_from_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef FLOAT_FROM_CHARS_TEST_CASES_HPP
+#define FLOAT_FROM_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+#include <stddef.h>
+#include <system_error>
+using namespace std;
+
+inline constexpr FloatFromCharsTestCase float_from_chars_test_cases[] = {
+    {"1.a0000400", chars_format::hex, 10, errc{}, 0x1.a00004p0f}, // exact
+    {"1.a0000401", chars_format::hex, 10, errc{}, 0x1.a00004p0f}, // below midpoint, round down
+    {"1.a0000500", chars_format::hex, 10, errc{}, 0x1.a00004p0f}, // midpoint, round down to even
+    {"1.a0000501", chars_format::hex, 10, errc{}, 0x1.a00006p0f}, // above midpoint, round up
+    {"1.a0000600", chars_format::hex, 10, errc{}, 0x1.a00006p0f}, // exact
+    {"1.a0000601", chars_format::hex, 10, errc{}, 0x1.a00006p0f}, // below midpoint, round down
+    {"1.a0000700", chars_format::hex, 10, errc{}, 0x1.a00008p0f}, // midpoint, round up to even
+    {"1.a0000701", chars_format::hex, 10, errc{}, 0x1.a00008p0f}, // above midpoint, round up
+
+    {"1.0000040", chars_format::hex, 9, errc{}, 0x1.000004p0f}, // exact
+    {"1.0000041", chars_format::hex, 9, errc{}, 0x1.000004p0f}, // below midpoint, round down
+    {"1.0000050", chars_format::hex, 9, errc{}, 0x1.000004p0f}, // midpoint, round down to even
+    {"1.0000051", chars_format::hex, 9, errc{}, 0x1.000006p0f}, // above midpoint, round up
+    {"1.0000060", chars_format::hex, 9, errc{}, 0x1.000006p0f}, // exact
+    {"1.0000061", chars_format::hex, 9, errc{}, 0x1.000006p0f}, // below midpoint, round down
+    {"1.0000070", chars_format::hex, 9, errc{}, 0x1.000008p0f}, // midpoint, round up to even
+    {"1.0000071", chars_format::hex, 9, errc{}, 0x1.000008p0f}, // above midpoint, round up
+
+    {"1.0000002384185791015625000000", chars_format::general, 30, errc{}, 0x1.000004p0f}, // exact
+    {"1.0000002421438694000244140625", chars_format::general, 30, errc{}, 0x1.000004p0f}, // below midpoint, round down
+    {"1.0000002980232238769531249999", chars_format::general, 30, errc{}, 0x1.000004p0f}, // below midpoint, round down
+    {"1.0000002980232238769531250000", chars_format::general, 30, errc{},
+        0x1.000004p0f}, // midpoint, round down to even
+    {"1.0000002980232238769531250001", chars_format::general, 30, errc{}, 0x1.000006p0f}, // above midpoint, round up
+    {"1.0000003017485141754150390625", chars_format::general, 30, errc{}, 0x1.000006p0f}, // above midpoint, round up
+    {"1.0000003576278686523437500000", chars_format::general, 30, errc{}, 0x1.000006p0f}, // exact
+    {"1.0000003613531589508056640625", chars_format::general, 30, errc{}, 0x1.000006p0f}, // below midpoint, round down
+    {"1.0000004172325134277343749999", chars_format::general, 30, errc{}, 0x1.000006p0f}, // below midpoint, round down
+    {"1.0000004172325134277343750000", chars_format::general, 30, errc{}, 0x1.000008p0f}, // midpoint, round up to even
+    {"1.0000004172325134277343750001", chars_format::general, 30, errc{}, 0x1.000008p0f}, // above midpoint, round up
+    {"1.0000004209578037261962890625", chars_format::general, 30, errc{}, 0x1.000008p0f}, // above midpoint, round up
+
+    // VSO-838635 "<charconv>: from_chars() mishandles certain subnormals"
+    // This bug didn't actually affect float, but we should have similar test cases.
+    // These values change on half-ulp boundaries:
+    // 1 * 2^-150 ~= 7.01e-46 (half-ulp between zero and min subnormal)
+    // 2 * 2^-150 ~= 1.40e-45 (min subnormal)
+    // 3 * 2^-150 ~= 2.10e-45 (half-ulp between min subnormal and next subnormal)
+    // 4 * 2^-150 ~= 2.80e-45 (next subnormal)
+    {"6."
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666666"
+     "6666666666666666666e-46",
+        chars_format::scientific, 1006, errc::result_out_of_range, 0x0.000000p+0f},
+    {"7."
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777777"
+     "7777777777777777777e-46",
+        chars_format::scientific, 1006, errc{}, 0x0.000002p-126f},
+    {"8."
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888888"
+     "8888888888888888888e-46",
+        chars_format::scientific, 1006, errc{}, 0x0.000002p-126f},
+    {"9."
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999999"
+     "9999999999999999999e-46",
+        chars_format::scientific, 1006, errc{}, 0x0.000002p-126f},
+    {"1."
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
+     "1111111111111111111e-45",
+        chars_format::scientific, 1006, errc{}, 0x0.000002p-126f},
+    {"2."
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222222"
+     "2222222222222222222e-45",
+        chars_format::scientific, 1006, errc{}, 0x0.000004p-126f},
+
+    // VSO-733765 "<charconv>: [Feedback] double std::from_chars behavior on exponent out of range"
+    // LWG-3081 "Floating point from_chars API does not distinguish between overflow and underflow"
+    // These test cases exercise every overflow/underflow codepath.
+    {"1e+1000", chars_format::scientific, 7, errc::result_out_of_range, float_inf},
+    {"1e-1000", chars_format::scientific, 7, errc::result_out_of_range, 0.0f},
+    {"1.ffffffp+127", chars_format::hex, 13, errc::result_out_of_range, float_inf},
+    {"1e+2000", chars_format::scientific, 7, errc::result_out_of_range, float_inf},
+    {"1e-2000", chars_format::scientific, 7, errc::result_out_of_range, 0.0f},
+    {"1e+9999", chars_format::scientific, 7, errc::result_out_of_range, float_inf},
+    {"1e-9999", chars_format::scientific, 7, errc::result_out_of_range, 0.0f},
+    {"10e+5199", chars_format::scientific, 8, errc::result_out_of_range, float_inf},
+    {"0.001e-5199", chars_format::scientific, 11, errc::result_out_of_range, 0.0f},
+};
+
+#endif // FLOAT_FROM_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/float_general_precision_to_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef FLOAT_GENERAL_PRECISION_TO_CHARS_TEST_CASES_HPP
+#define FLOAT_GENERAL_PRECISION_TO_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+// C11 7.21.6.1 "The fprintf function"/8:
+
+// "Then, if a conversion with style E would have an exponent of X:
+// - if P > X >= -4, the conversion is with style f (or F) and precision P - (X + 1).
+// - otherwise, the conversion is with style e (or E) and precision P - 1."
+
+// "Finally, [...] any trailing zeros are removed from the fractional portion of the result
+// and the decimal-point character is removed if there is no fractional portion remaining."
+
+inline constexpr FloatPrecisionToCharsTestCase float_general_precision_to_chars_test_cases[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0f, chars_format::general, 4, "0"},
+    {-0.0f, chars_format::general, 4, "-0"},
+    {float_inf, chars_format::general, 4, "inf"},
+    {-float_inf, chars_format::general, 4, "-inf"},
+    {float_nan, chars_format::general, 4, "nan"},
+    {-float_nan, chars_format::general, 4, "-nan(ind)"},
+    {float_nan_payload, chars_format::general, 4, "nan"},
+    {-float_nan_payload, chars_format::general, 4, "-nan"},
+    {1.729f, chars_format::general, 4, "1.729"},
+    {-1.729f, chars_format::general, 4, "-1.729"},
+
+    // Test corner cases.
+    {0x0.000002p-126f, chars_format::general, 1000,
+        "1.40129846432481707092372958328991613128026194187651577175706828388979108268586060148663818836212158203125"
+        "e-45"}, // min subnormal
+    {0x0.fffffep-126f, chars_format::general, 1000,
+        "1."
+        "17549421069244107548702944484928734882705242874589333385717453057158887047561890426550235133618116378784179687"
+        "5e-38"}, // max subnormal
+    {0x1p-126f, chars_format::general, 1000,
+        "1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38"}, // min normal
+    {0x1.fffffep+127f, chars_format::general, 1000, "340282346638528859811704183484516925440"}, // max normal
+
+    {0x0.000002p-126f, chars_format::general, 6, "1.4013e-45"}, // min subnormal
+    {0x0.fffffep-126f, chars_format::general, 6, "1.17549e-38"}, // max subnormal
+    {0x1p-126f, chars_format::general, 6, "1.17549e-38"}, // min normal
+    {0x1.fffffep+127f, chars_format::general, 6, "3.40282e+38"}, // max normal
+
+    // Test maximum-length output (excluding minus signs).
+    {0x1.fffffep-126f, chars_format::general, 1000,
+        "2."
+        "35098856151472858345576598207153302664571798551798085536592623685000612993034607711706485133618116378784179687"
+        "5e-38"}, // scientific, happens to be the same length as max subnormal
+    {0x1.fffffep-14f, chars_format::general, 1000, "0.0001220703052240423858165740966796875"}, // fixed
+
+    // Test varying precision. Negative precision requests P == 6. Zero precision requests P == 1.
+    // Here, the scientific exponent X is 0.
+    // Therefore, fixed notation is always chosen with precision P - (X + 1) == P - 1.
+    {0x1.b04p0f, chars_format::general, -2, "1.68848"},
+    {0x1.b04p0f, chars_format::general, -1, "1.68848"},
+    {0x1.b04p0f, chars_format::general, 0, "2"},
+    {0x1.b04p0f, chars_format::general, 1, "2"}, // fixed notation trims decimal point
+    {0x1.b04p0f, chars_format::general, 2, "1.7"},
+    {0x1.b04p0f, chars_format::general, 3, "1.69"},
+    {0x1.b04p0f, chars_format::general, 4, "1.688"},
+    {0x1.b04p0f, chars_format::general, 5, "1.6885"},
+    {0x1.b04p0f, chars_format::general, 6, "1.68848"},
+    {0x1.b04p0f, chars_format::general, 7, "1.688477"},
+    {0x1.b04p0f, chars_format::general, 8, "1.6884766"},
+    {0x1.b04p0f, chars_format::general, 9, "1.68847656"},
+    {0x1.b04p0f, chars_format::general, 10, "1.688476562"}, // round to even
+    {0x1.b04p0f, chars_format::general, 11, "1.6884765625"}, // exact
+    {0x1.b04p0f, chars_format::general, 12, "1.6884765625"}, // trim trailing zeros
+    {0x1.b04p0f, chars_format::general, 13, "1.6884765625"},
+
+    // Here, the scientific exponent X is -5.
+    // Therefore, scientific notation is always chosen with precision P - 1.
+    {0x1.8p-15f, chars_format::general, -2, "4.57764e-05"},
+    {0x1.8p-15f, chars_format::general, -1, "4.57764e-05"},
+    {0x1.8p-15f, chars_format::general, 0, "5e-05"},
+    {0x1.8p-15f, chars_format::general, 1, "5e-05"}, // scientific notation trims decimal point
+    {0x1.8p-15f, chars_format::general, 2, "4.6e-05"},
+    {0x1.8p-15f, chars_format::general, 3, "4.58e-05"},
+    {0x1.8p-15f, chars_format::general, 4, "4.578e-05"},
+    {0x1.8p-15f, chars_format::general, 5, "4.5776e-05"},
+    {0x1.8p-15f, chars_format::general, 6, "4.57764e-05"},
+    {0x1.8p-15f, chars_format::general, 7, "4.577637e-05"},
+    {0x1.8p-15f, chars_format::general, 8, "4.5776367e-05"},
+    {0x1.8p-15f, chars_format::general, 9, "4.57763672e-05"},
+    {0x1.8p-15f, chars_format::general, 10, "4.577636719e-05"},
+    {0x1.8p-15f, chars_format::general, 11, "4.5776367188e-05"}, // round to even
+    {0x1.8p-15f, chars_format::general, 12, "4.57763671875e-05"}, // exact
+    {0x1.8p-15f, chars_format::general, 13, "4.57763671875e-05"}, // trim trailing zeros
+    {0x1.8p-15f, chars_format::general, 14, "4.57763671875e-05"},
+
+    // Trim trailing zeros.
+    {0x1.80015p0f, chars_format::general, 1, "2"}, // fixed notation trims decimal point
+    {0x1.80015p0f, chars_format::general, 2, "1.5"},
+    {0x1.80015p0f, chars_format::general, 3, "1.5"}, // general trims trailing zeros
+    {0x1.80015p0f, chars_format::general, 4, "1.5"},
+    {0x1.80015p0f, chars_format::general, 5, "1.5"},
+    {0x1.80015p0f, chars_format::general, 6, "1.50002"},
+    {0x1.80015p0f, chars_format::general, 7, "1.50002"},
+    {0x1.80015p0f, chars_format::general, 8, "1.50002"},
+    {0x1.80015p0f, chars_format::general, 9, "1.50002003"},
+    {0x1.80015p0f, chars_format::general, 10, "1.500020027"},
+    {0x1.80015p0f, chars_format::general, 11, "1.5000200272"},
+    {0x1.80015p0f, chars_format::general, 12, "1.50002002716"},
+    {0x1.80015p0f, chars_format::general, 13, "1.500020027161"},
+    {0x1.80015p0f, chars_format::general, 14, "1.5000200271606"},
+    {0x1.80015p0f, chars_format::general, 15, "1.50002002716064"},
+    {0x1.80015p0f, chars_format::general, 16, "1.500020027160645"},
+    {0x1.80015p0f, chars_format::general, 17, "1.5000200271606445"},
+    {0x1.80015p0f, chars_format::general, 18, "1.50002002716064453"},
+    {0x1.80015p0f, chars_format::general, 19, "1.500020027160644531"},
+    {0x1.80015p0f, chars_format::general, 20, "1.5000200271606445312"}, // round to even
+    {0x1.80015p0f, chars_format::general, 21, "1.50002002716064453125"}, // exact
+
+    // Trim trailing zeros and decimal point.
+    {0x1.00015p0f, chars_format::general, 1, "1"}, // fixed notation trims decimal point
+    {0x1.00015p0f, chars_format::general, 2, "1"}, // general trims decimal point and trailing zeros
+    {0x1.00015p0f, chars_format::general, 3, "1"},
+    {0x1.00015p0f, chars_format::general, 4, "1"},
+    {0x1.00015p0f, chars_format::general, 5, "1"},
+    {0x1.00015p0f, chars_format::general, 6, "1.00002"},
+    {0x1.00015p0f, chars_format::general, 7, "1.00002"},
+    {0x1.00015p0f, chars_format::general, 8, "1.00002"},
+    {0x1.00015p0f, chars_format::general, 9, "1.00002003"},
+    {0x1.00015p0f, chars_format::general, 10, "1.000020027"},
+    {0x1.00015p0f, chars_format::general, 11, "1.0000200272"},
+    {0x1.00015p0f, chars_format::general, 12, "1.00002002716"},
+    {0x1.00015p0f, chars_format::general, 13, "1.000020027161"},
+    {0x1.00015p0f, chars_format::general, 14, "1.0000200271606"},
+    {0x1.00015p0f, chars_format::general, 15, "1.00002002716064"},
+    {0x1.00015p0f, chars_format::general, 16, "1.000020027160645"},
+    {0x1.00015p0f, chars_format::general, 17, "1.0000200271606445"},
+    {0x1.00015p0f, chars_format::general, 18, "1.00002002716064453"},
+    {0x1.00015p0f, chars_format::general, 19, "1.000020027160644531"},
+    {0x1.00015p0f, chars_format::general, 20, "1.0000200271606445312"}, // round to even
+    {0x1.00015p0f, chars_format::general, 21, "1.00002002716064453125"}, // exact
+
+    // Trim trailing zeros, scientific notation.
+    {0x1.5cf752p-20f, chars_format::general, 1, "1e-06"}, // scientific notation trims decimal point
+    {0x1.5cf752p-20f, chars_format::general, 2, "1.3e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 3, "1.3e-06"}, // general trims trailing zeros
+    {0x1.5cf752p-20f, chars_format::general, 4, "1.3e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 5, "1.3e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 6, "1.3e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 7, "1.3e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 8, "1.3e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 9, "1.30000001e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 10, "1.300000008e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 11, "1.3000000081e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 12, "1.30000000809e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 13, "1.300000008086e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 14, "1.3000000080865e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 15, "1.3000000080865e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 16, "1.300000008086499e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 17, "1.3000000080864993e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 18, "1.30000000808649929e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 19, "1.300000008086499292e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 20, "1.3000000080864992924e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 21, "1.3000000080864992924e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 22, "1.300000008086499292403e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 23, "1.3000000080864992924035e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 24, "1.30000000808649929240346e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 25, "1.30000000808649929240346e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 26, "1.3000000080864992924034595e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 27, "1.30000000808649929240345955e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 28, "1.300000008086499292403459549e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 29, "1.300000008086499292403459549e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 30, "1.30000000808649929240345954895e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 31, "1.30000000808649929240345954895e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 32, "1.3000000080864992924034595489502e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 33, "1.3000000080864992924034595489502e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 34, "1.300000008086499292403459548950195e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 35, "1.3000000080864992924034595489501953e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 36, "1.30000000808649929240345954895019531e-06"},
+    {0x1.5cf752p-20f, chars_format::general, 37, "1.300000008086499292403459548950195312e-06"}, // round to even
+    {0x1.5cf752p-20f, chars_format::general, 38, "1.3000000080864992924034595489501953125e-06"}, // exact
+
+    // Trim trailing zeros and decimal point, scientific notation.
+    {0x1.92a738p-19f, chars_format::general, 1, "3e-06"}, // scientific notation trims decimal point
+    {0x1.92a738p-19f, chars_format::general, 2, "3e-06"}, // general trims decimal point and trailing zeros
+    {0x1.92a738p-19f, chars_format::general, 3, "3e-06"},
+    {0x1.92a738p-19f, chars_format::general, 4, "3e-06"},
+    {0x1.92a738p-19f, chars_format::general, 5, "3e-06"},
+    {0x1.92a738p-19f, chars_format::general, 6, "3e-06"},
+    {0x1.92a738p-19f, chars_format::general, 7, "3e-06"},
+    {0x1.92a738p-19f, chars_format::general, 8, "3.0000001e-06"},
+    {0x1.92a738p-19f, chars_format::general, 9, "3.00000011e-06"},
+    {0x1.92a738p-19f, chars_format::general, 10, "3.000000106e-06"},
+    {0x1.92a738p-19f, chars_format::general, 11, "3.0000001061e-06"},
+    {0x1.92a738p-19f, chars_format::general, 12, "3.00000010611e-06"},
+    {0x1.92a738p-19f, chars_format::general, 13, "3.000000106113e-06"},
+    {0x1.92a738p-19f, chars_format::general, 14, "3.0000001061126e-06"},
+    {0x1.92a738p-19f, chars_format::general, 15, "3.00000010611257e-06"},
+    {0x1.92a738p-19f, chars_format::general, 16, "3.000000106112566e-06"},
+    {0x1.92a738p-19f, chars_format::general, 17, "3.0000001061125658e-06"},
+    {0x1.92a738p-19f, chars_format::general, 18, "3.00000010611256585e-06"},
+    {0x1.92a738p-19f, chars_format::general, 19, "3.000000106112565845e-06"},
+    {0x1.92a738p-19f, chars_format::general, 20, "3.0000001061125658453e-06"},
+    {0x1.92a738p-19f, chars_format::general, 21, "3.00000010611256584525e-06"},
+    {0x1.92a738p-19f, chars_format::general, 22, "3.000000106112565845251e-06"},
+    {0x1.92a738p-19f, chars_format::general, 23, "3.0000001061125658452511e-06"},
+    {0x1.92a738p-19f, chars_format::general, 24, "3.00000010611256584525108e-06"},
+    {0x1.92a738p-19f, chars_format::general, 25, "3.000000106112565845251083e-06"},
+    {0x1.92a738p-19f, chars_format::general, 26, "3.0000001061125658452510834e-06"},
+    {0x1.92a738p-19f, chars_format::general, 27, "3.00000010611256584525108337e-06"},
+    {0x1.92a738p-19f, chars_format::general, 28, "3.000000106112565845251083374e-06"},
+    {0x1.92a738p-19f, chars_format::general, 29, "3.000000106112565845251083374e-06"},
+    {0x1.92a738p-19f, chars_format::general, 30, "3.00000010611256584525108337402e-06"},
+    {0x1.92a738p-19f, chars_format::general, 31, "3.000000106112565845251083374023e-06"},
+    {0x1.92a738p-19f, chars_format::general, 32, "3.0000001061125658452510833740234e-06"},
+    {0x1.92a738p-19f, chars_format::general, 33, "3.00000010611256584525108337402344e-06"},
+    {0x1.92a738p-19f, chars_format::general, 34, "3.000000106112565845251083374023438e-06"}, // round to even
+    {0x1.92a738p-19f, chars_format::general, 35, "3.0000001061125658452510833740234375e-06"}, // exact
+
+    // Test a large precision with fixed notation and scientific notation,
+    // verifying that we remain within the bounds of any lookup tables.
+    {0x1.ba9fbep+0f, chars_format::general, 5000, "1.72899997234344482421875"},
+    {0x1.d01ffap-20f, chars_format::general, 5000, "1.7290000187131226994097232818603515625e-06"},
+
+    // Test the transitions between fixed notation and scientific notation.
+    {5555555.0f, chars_format::general, 1, "6e+06"},
+    {555555.0f, chars_format::general, 1, "6e+05"},
+    {55555.0f, chars_format::general, 1, "6e+04"},
+    {5555.0f, chars_format::general, 1, "6e+03"},
+    {555.0f, chars_format::general, 1, "6e+02"},
+    {55.0f, chars_format::general, 1, "6e+01"}, // round to even
+    {5.0f, chars_format::general, 1, "5"},
+    {0x1p-3f, chars_format::general, 1, "0.1"}, // 0.125
+    {0x1p-6f, chars_format::general, 1, "0.02"}, // 0.015625
+    {0x1p-9f, chars_format::general, 1, "0.002"}, // 0.001953125
+    {0x1p-13f, chars_format::general, 1, "0.0001"}, // 0.0001220703125
+    {0x1p-16f, chars_format::general, 1, "2e-05"}, // 1.52587890625e-05
+    {0x1p-19f, chars_format::general, 1, "2e-06"}, // 1.9073486328125e-06
+
+    {5555555.0f, chars_format::general, 2, "5.6e+06"},
+    {555555.0f, chars_format::general, 2, "5.6e+05"},
+    {55555.0f, chars_format::general, 2, "5.6e+04"},
+    {5555.0f, chars_format::general, 2, "5.6e+03"},
+    {555.0f, chars_format::general, 2, "5.6e+02"}, // round to even
+    {55.0f, chars_format::general, 2, "55"},
+    {5.0f, chars_format::general, 2, "5"},
+    {0x1p-3f, chars_format::general, 2, "0.12"}, // round to even
+    {0x1p-6f, chars_format::general, 2, "0.016"},
+    {0x1p-9f, chars_format::general, 2, "0.002"},
+    {0x1p-13f, chars_format::general, 2, "0.00012"},
+    {0x1p-16f, chars_format::general, 2, "1.5e-05"},
+    {0x1p-19f, chars_format::general, 2, "1.9e-06"},
+
+    {5555555.0f, chars_format::general, 3, "5.56e+06"},
+    {555555.0f, chars_format::general, 3, "5.56e+05"},
+    {55555.0f, chars_format::general, 3, "5.56e+04"},
+    {5555.0f, chars_format::general, 3, "5.56e+03"}, // round to even
+    {555.0f, chars_format::general, 3, "555"},
+    {55.0f, chars_format::general, 3, "55"},
+    {5.0f, chars_format::general, 3, "5"},
+    {0x1p-3f, chars_format::general, 3, "0.125"},
+    {0x1p-6f, chars_format::general, 3, "0.0156"},
+    {0x1p-9f, chars_format::general, 3, "0.00195"},
+    {0x1p-13f, chars_format::general, 3, "0.000122"},
+    {0x1p-16f, chars_format::general, 3, "1.53e-05"},
+    {0x1p-19f, chars_format::general, 3, "1.91e-06"},
+
+    {5555555.0f, chars_format::general, 4, "5.556e+06"},
+    {555555.0f, chars_format::general, 4, "5.556e+05"},
+    {55555.0f, chars_format::general, 4, "5.556e+04"}, // round to even
+    {5555.0f, chars_format::general, 4, "5555"},
+    {555.0f, chars_format::general, 4, "555"},
+    {55.0f, chars_format::general, 4, "55"},
+    {5.0f, chars_format::general, 4, "5"},
+    {0x1p-3f, chars_format::general, 4, "0.125"},
+    {0x1p-6f, chars_format::general, 4, "0.01562"}, // round to even
+    {0x1p-9f, chars_format::general, 4, "0.001953"},
+    {0x1p-13f, chars_format::general, 4, "0.0001221"},
+    {0x1p-16f, chars_format::general, 4, "1.526e-05"},
+    {0x1p-19f, chars_format::general, 4, "1.907e-06"},
+
+    {5555555.0f, chars_format::general, 5, "5.5556e+06"},
+    {555555.0f, chars_format::general, 5, "5.5556e+05"}, // round to even
+    {55555.0f, chars_format::general, 5, "55555"},
+    {5555.0f, chars_format::general, 5, "5555"},
+    {555.0f, chars_format::general, 5, "555"},
+    {55.0f, chars_format::general, 5, "55"},
+    {5.0f, chars_format::general, 5, "5"},
+    {0x1p-3f, chars_format::general, 5, "0.125"},
+    {0x1p-6f, chars_format::general, 5, "0.015625"},
+    {0x1p-9f, chars_format::general, 5, "0.0019531"},
+    {0x1p-13f, chars_format::general, 5, "0.00012207"},
+    {0x1p-16f, chars_format::general, 5, "1.5259e-05"},
+    {0x1p-19f, chars_format::general, 5, "1.9073e-06"},
+
+    // Tricky corner cases.
+    // In these scenarios, rounding can adjust the scientific exponent X,
+    // which affects the transition between fixed notation and scientific notation.
+    {999.999f, chars_format::general, 1, "1e+03"}, // "%.0e" is "1e+03"; X == 3
+    {999.999f, chars_format::general, 2, "1e+03"}, // "%.1e" is "1.0e+03"; X == 3
+    {999.999f, chars_format::general, 3, "1e+03"}, // "%.2e" is "1.00e+03"; X == 3
+    {999.999f, chars_format::general, 4, "1000"}, // "%.3e" is "1.000e+03"; X == 3
+    {999.999f, chars_format::general, 5, "1000"}, // "%.4e" is "1.0000e+03"; X == 3
+    {999.999f, chars_format::general, 6, "999.999"}, // "%.5e" is "9.99999e+02"; X == 2
+
+    {999.99f, chars_format::general, 1, "1e+03"},
+    {999.99f, chars_format::general, 2, "1e+03"},
+    {999.99f, chars_format::general, 3, "1e+03"},
+    {999.99f, chars_format::general, 4, "1000"},
+    {999.99f, chars_format::general, 5, "999.99"},
+    {999.99f, chars_format::general, 6, "999.99"},
+
+    // C11's Standardese is slightly vague about how to perform the trial formatting in scientific notation,
+    // but the intention is to use precision P - 1, which is what's used when scientific notation is actually chosen.
+    // This example verifies this behavior. Here, P == 3 performs trial formatting with "%.2e", triggering rounding.
+    // That increases X to 3, forcing scientific notation to be chosen.
+    // If P == 3 performed trial formatting with "%.3e", rounding wouldn't happen,
+    // X would be 2, and fixed notation would be chosen.
+    {999.9f, chars_format::general, 1, "1e+03"}, // "%.0e" is "1e+03"; X == 3
+    {999.9f, chars_format::general, 2, "1e+03"}, // "%.1e" is "1.0e+03"; X == 3
+    {999.9f, chars_format::general, 3, "1e+03"}, // "%.2e" is "1.00e+03"; X == 3; SPECIAL CORNER CASE
+    {999.9f, chars_format::general, 4, "999.9"}, // "%.3e" is "9.999e+02"; X == 2
+    {999.9f, chars_format::general, 5, "999.9"}, // "%.4e" is "9.9990e+02"; X == 2
+    {999.9f, chars_format::general, 6, "999.9"}, // "%.5e" is "9.99900e+02"; X == 2
+
+    {999.0f, chars_format::general, 1, "1e+03"},
+    {999.0f, chars_format::general, 2, "1e+03"},
+    {999.0f, chars_format::general, 3, "999"},
+    {999.0f, chars_format::general, 4, "999"},
+    {999.0f, chars_format::general, 5, "999"},
+    {999.0f, chars_format::general, 6, "999"},
+
+    {99.9999f, chars_format::general, 1, "1e+02"},
+    {99.9999f, chars_format::general, 2, "1e+02"},
+    {99.9999f, chars_format::general, 3, "100"},
+    {99.9999f, chars_format::general, 4, "100"},
+    {99.9999f, chars_format::general, 5, "100"},
+    {99.9999f, chars_format::general, 6, "99.9999"},
+
+    {99.999f, chars_format::general, 1, "1e+02"},
+    {99.999f, chars_format::general, 2, "1e+02"},
+    {99.999f, chars_format::general, 3, "100"},
+    {99.999f, chars_format::general, 4, "100"},
+    {99.999f, chars_format::general, 5, "99.999"},
+    {99.999f, chars_format::general, 6, "99.999"},
+
+    {99.99f, chars_format::general, 1, "1e+02"},
+    {99.99f, chars_format::general, 2, "1e+02"},
+    {99.99f, chars_format::general, 3, "100"},
+    {99.99f, chars_format::general, 4, "99.99"},
+    {99.99f, chars_format::general, 5, "99.99"},
+    {99.99f, chars_format::general, 6, "99.99"},
+
+    {99.9f, chars_format::general, 1, "1e+02"},
+    {99.9f, chars_format::general, 2, "1e+02"},
+    {99.9f, chars_format::general, 3, "99.9"},
+    {99.9f, chars_format::general, 4, "99.9"},
+    {99.9f, chars_format::general, 5, "99.9"},
+    {99.9f, chars_format::general, 6, "99.9"},
+
+    {99.0f, chars_format::general, 1, "1e+02"},
+    {99.0f, chars_format::general, 2, "99"},
+    {99.0f, chars_format::general, 3, "99"},
+    {99.0f, chars_format::general, 4, "99"},
+    {99.0f, chars_format::general, 5, "99"},
+    {99.0f, chars_format::general, 6, "99"},
+
+    {9.99999f, chars_format::general, 1, "1e+01"},
+    {9.99999f, chars_format::general, 2, "10"},
+    {9.99999f, chars_format::general, 3, "10"},
+    {9.99999f, chars_format::general, 4, "10"},
+    {9.99999f, chars_format::general, 5, "10"},
+    {9.99999f, chars_format::general, 6, "9.99999"},
+
+    {9.9999f, chars_format::general, 1, "1e+01"},
+    {9.9999f, chars_format::general, 2, "10"},
+    {9.9999f, chars_format::general, 3, "10"},
+    {9.9999f, chars_format::general, 4, "10"},
+    {9.9999f, chars_format::general, 5, "9.9999"},
+    {9.9999f, chars_format::general, 6, "9.9999"},
+
+    {9.999f, chars_format::general, 1, "1e+01"},
+    {9.999f, chars_format::general, 2, "10"},
+    {9.999f, chars_format::general, 3, "10"},
+    {9.999f, chars_format::general, 4, "9.999"},
+    {9.999f, chars_format::general, 5, "9.999"},
+    {9.999f, chars_format::general, 6, "9.999"},
+
+    {9.99f, chars_format::general, 1, "1e+01"},
+    {9.99f, chars_format::general, 2, "10"},
+    {9.99f, chars_format::general, 3, "9.99"},
+    {9.99f, chars_format::general, 4, "9.99"},
+    {9.99f, chars_format::general, 5, "9.99"},
+    {9.99f, chars_format::general, 6, "9.99"},
+
+    {9.9f, chars_format::general, 1, "1e+01"},
+    {9.9f, chars_format::general, 2, "9.9"},
+    {9.9f, chars_format::general, 3, "9.9"},
+    {9.9f, chars_format::general, 4, "9.9"},
+    {9.9f, chars_format::general, 5, "9.9"},
+    {9.9f, chars_format::general, 6, "9.9"},
+
+    {9.0f, chars_format::general, 1, "9"},
+    {9.0f, chars_format::general, 2, "9"},
+    {9.0f, chars_format::general, 3, "9"},
+    {9.0f, chars_format::general, 4, "9"},
+    {9.0f, chars_format::general, 5, "9"},
+    {9.0f, chars_format::general, 6, "9"},
+
+    {0.999999f, chars_format::general, 1, "1"},
+    {0.999999f, chars_format::general, 2, "1"},
+    {0.999999f, chars_format::general, 3, "1"},
+    {0.999999f, chars_format::general, 4, "1"},
+    {0.999999f, chars_format::general, 5, "1"},
+    {0.999999f, chars_format::general, 6, "0.999999"},
+
+    {0.99999f, chars_format::general, 1, "1"},
+    {0.99999f, chars_format::general, 2, "1"},
+    {0.99999f, chars_format::general, 3, "1"},
+    {0.99999f, chars_format::general, 4, "1"},
+    {0.99999f, chars_format::general, 5, "0.99999"},
+    {0.99999f, chars_format::general, 6, "0.99999"},
+
+    {0.9999f, chars_format::general, 1, "1"},
+    {0.9999f, chars_format::general, 2, "1"},
+    {0.9999f, chars_format::general, 3, "1"},
+    {0.9999f, chars_format::general, 4, "0.9999"},
+    {0.9999f, chars_format::general, 5, "0.9999"},
+    {0.9999f, chars_format::general, 6, "0.9999"},
+
+    {0.999f, chars_format::general, 1, "1"},
+    {0.999f, chars_format::general, 2, "1"},
+    {0.999f, chars_format::general, 3, "0.999"},
+    {0.999f, chars_format::general, 4, "0.999"},
+    {0.999f, chars_format::general, 5, "0.999"},
+    {0.999f, chars_format::general, 6, "0.999"},
+
+    {0.99f, chars_format::general, 1, "1"},
+    {0.99f, chars_format::general, 2, "0.99"},
+    {0.99f, chars_format::general, 3, "0.99"},
+    {0.99f, chars_format::general, 4, "0.99"},
+    {0.99f, chars_format::general, 5, "0.99"},
+    {0.99f, chars_format::general, 6, "0.99"},
+
+    {0.9f, chars_format::general, 1, "0.9"},
+    {0.9f, chars_format::general, 2, "0.9"},
+    {0.9f, chars_format::general, 3, "0.9"},
+    {0.9f, chars_format::general, 4, "0.9"},
+    {0.9f, chars_format::general, 5, "0.9"},
+    {0.9f, chars_format::general, 6, "0.9"},
+
+    {0.0999999f, chars_format::general, 1, "0.1"},
+    {0.0999999f, chars_format::general, 2, "0.1"},
+    {0.0999999f, chars_format::general, 3, "0.1"},
+    {0.0999999f, chars_format::general, 4, "0.1"},
+    {0.0999999f, chars_format::general, 5, "0.1"},
+    {0.0999999f, chars_format::general, 6, "0.0999999"},
+
+    {0.099999f, chars_format::general, 1, "0.1"},
+    {0.099999f, chars_format::general, 2, "0.1"},
+    {0.099999f, chars_format::general, 3, "0.1"},
+    {0.099999f, chars_format::general, 4, "0.1"},
+    {0.099999f, chars_format::general, 5, "0.099999"},
+    {0.099999f, chars_format::general, 6, "0.099999"},
+
+    {0.09999f, chars_format::general, 1, "0.1"},
+    {0.09999f, chars_format::general, 2, "0.1"},
+    {0.09999f, chars_format::general, 3, "0.1"},
+    {0.09999f, chars_format::general, 4, "0.09999"},
+    {0.09999f, chars_format::general, 5, "0.09999"},
+    {0.09999f, chars_format::general, 6, "0.09999"},
+
+    {0.0999f, chars_format::general, 1, "0.1"},
+    {0.0999f, chars_format::general, 2, "0.1"},
+    {0.0999f, chars_format::general, 3, "0.0999"},
+    {0.0999f, chars_format::general, 4, "0.0999"},
+    {0.0999f, chars_format::general, 5, "0.0999"},
+    {0.0999f, chars_format::general, 6, "0.0999"},
+
+    {0.099f, chars_format::general, 1, "0.1"},
+    {0.099f, chars_format::general, 2, "0.099"},
+    {0.099f, chars_format::general, 3, "0.099"},
+    {0.099f, chars_format::general, 4, "0.099"},
+    {0.099f, chars_format::general, 5, "0.099"},
+    {0.099f, chars_format::general, 6, "0.099"},
+
+    {0.09f, chars_format::general, 1, "0.09"},
+    {0.09f, chars_format::general, 2, "0.09"},
+    {0.09f, chars_format::general, 3, "0.09"},
+    {0.09f, chars_format::general, 4, "0.09"},
+    {0.09f, chars_format::general, 5, "0.09"},
+    {0.09f, chars_format::general, 6, "0.09"},
+
+    {0.00999999f, chars_format::general, 1, "0.01"},
+    {0.00999999f, chars_format::general, 2, "0.01"},
+    {0.00999999f, chars_format::general, 3, "0.01"},
+    {0.00999999f, chars_format::general, 4, "0.01"},
+    {0.00999999f, chars_format::general, 5, "0.01"},
+    {0.00999999f, chars_format::general, 6, "0.00999999"},
+
+    {0.0099999f, chars_format::general, 1, "0.01"},
+    {0.0099999f, chars_format::general, 2, "0.01"},
+    {0.0099999f, chars_format::general, 3, "0.01"},
+    {0.0099999f, chars_format::general, 4, "0.01"},
+    {0.0099999f, chars_format::general, 5, "0.0099999"},
+    {0.0099999f, chars_format::general, 6, "0.0099999"},
+
+    {0.009999f, chars_format::general, 1, "0.01"},
+    {0.009999f, chars_format::general, 2, "0.01"},
+    {0.009999f, chars_format::general, 3, "0.01"},
+    {0.009999f, chars_format::general, 4, "0.009999"},
+    {0.009999f, chars_format::general, 5, "0.009999"},
+    {0.009999f, chars_format::general, 6, "0.009999"},
+
+    {0.00999f, chars_format::general, 1, "0.01"},
+    {0.00999f, chars_format::general, 2, "0.01"},
+    {0.00999f, chars_format::general, 3, "0.00999"},
+    {0.00999f, chars_format::general, 4, "0.00999"},
+    {0.00999f, chars_format::general, 5, "0.00999"},
+    {0.00999f, chars_format::general, 6, "0.00999"},
+
+    {0.0099f, chars_format::general, 1, "0.01"},
+    {0.0099f, chars_format::general, 2, "0.0099"},
+    {0.0099f, chars_format::general, 3, "0.0099"},
+    {0.0099f, chars_format::general, 4, "0.0099"},
+    {0.0099f, chars_format::general, 5, "0.0099"},
+    {0.0099f, chars_format::general, 6, "0.0099"},
+
+    {0.009f, chars_format::general, 1, "0.009"},
+    {0.009f, chars_format::general, 2, "0.009"},
+    {0.009f, chars_format::general, 3, "0.009"},
+    {0.009f, chars_format::general, 4, "0.009"},
+    {0.009f, chars_format::general, 5, "0.009"},
+    {0.009f, chars_format::general, 6, "0.009"},
+
+    {0.000999999f, chars_format::general, 1, "0.001"},
+    {0.000999999f, chars_format::general, 2, "0.001"},
+    {0.000999999f, chars_format::general, 3, "0.001"},
+    {0.000999999f, chars_format::general, 4, "0.001"},
+    {0.000999999f, chars_format::general, 5, "0.001"},
+    {0.000999999f, chars_format::general, 6, "0.000999999"},
+
+    {0.00099999f, chars_format::general, 1, "0.001"},
+    {0.00099999f, chars_format::general, 2, "0.001"},
+    {0.00099999f, chars_format::general, 3, "0.001"},
+    {0.00099999f, chars_format::general, 4, "0.001"},
+    {0.00099999f, chars_format::general, 5, "0.00099999"},
+    {0.00099999f, chars_format::general, 6, "0.00099999"},
+
+    {0.0009999f, chars_format::general, 1, "0.001"},
+    {0.0009999f, chars_format::general, 2, "0.001"},
+    {0.0009999f, chars_format::general, 3, "0.001"},
+    {0.0009999f, chars_format::general, 4, "0.0009999"},
+    {0.0009999f, chars_format::general, 5, "0.0009999"},
+    {0.0009999f, chars_format::general, 6, "0.0009999"},
+
+    {0.000999f, chars_format::general, 1, "0.001"},
+    {0.000999f, chars_format::general, 2, "0.001"},
+    {0.000999f, chars_format::general, 3, "0.000999"},
+    {0.000999f, chars_format::general, 4, "0.000999"},
+    {0.000999f, chars_format::general, 5, "0.000999"},
+    {0.000999f, chars_format::general, 6, "0.000999"},
+
+    {0.00099f, chars_format::general, 1, "0.001"},
+    {0.00099f, chars_format::general, 2, "0.00099"},
+    {0.00099f, chars_format::general, 3, "0.00099"},
+    {0.00099f, chars_format::general, 4, "0.00099"},
+    {0.00099f, chars_format::general, 5, "0.00099"},
+    {0.00099f, chars_format::general, 6, "0.00099"},
+
+    {0.0009f, chars_format::general, 1, "0.0009"},
+    {0.0009f, chars_format::general, 2, "0.0009"},
+    {0.0009f, chars_format::general, 3, "0.0009"},
+    {0.0009f, chars_format::general, 4, "0.0009"},
+    {0.0009f, chars_format::general, 5, "0.0009"},
+    {0.0009f, chars_format::general, 6, "0.0009"},
+
+    // Having a scientific exponent X == -5 triggers scientific notation.
+    // If rounding adjusts this to X == -4, then fixed notation will be selected.
+    {0.0000999999f, chars_format::general, 1, "0.0001"},
+    {0.0000999999f, chars_format::general, 2, "0.0001"},
+    {0.0000999999f, chars_format::general, 3, "0.0001"},
+    {0.0000999999f, chars_format::general, 4, "0.0001"},
+    {0.0000999999f, chars_format::general, 5, "0.0001"},
+    {0.0000999999f, chars_format::general, 6, "9.99999e-05"},
+
+    {0.000099999f, chars_format::general, 1, "0.0001"},
+    {0.000099999f, chars_format::general, 2, "0.0001"},
+    {0.000099999f, chars_format::general, 3, "0.0001"},
+    {0.000099999f, chars_format::general, 4, "0.0001"},
+    {0.000099999f, chars_format::general, 5, "9.9999e-05"},
+    {0.000099999f, chars_format::general, 6, "9.9999e-05"},
+
+    {0.00009999f, chars_format::general, 1, "0.0001"},
+    {0.00009999f, chars_format::general, 2, "0.0001"},
+    {0.00009999f, chars_format::general, 3, "0.0001"},
+    {0.00009999f, chars_format::general, 4, "9.999e-05"},
+    {0.00009999f, chars_format::general, 5, "9.999e-05"},
+    {0.00009999f, chars_format::general, 6, "9.999e-05"},
+
+    {0.0000999f, chars_format::general, 1, "0.0001"},
+    {0.0000999f, chars_format::general, 2, "0.0001"},
+    {0.0000999f, chars_format::general, 3, "9.99e-05"},
+    {0.0000999f, chars_format::general, 4, "9.99e-05"},
+    {0.0000999f, chars_format::general, 5, "9.99e-05"},
+    {0.0000999f, chars_format::general, 6, "9.99e-05"},
+
+    {0.000099f, chars_format::general, 1, "0.0001"},
+    {0.000099f, chars_format::general, 2, "9.9e-05"},
+    {0.000099f, chars_format::general, 3, "9.9e-05"},
+    {0.000099f, chars_format::general, 4, "9.9e-05"},
+    {0.000099f, chars_format::general, 5, "9.9e-05"},
+    {0.000099f, chars_format::general, 6, "9.9e-05"},
+
+    {0.00009f, chars_format::general, 1, "9e-05"},
+    {0.00009f, chars_format::general, 2, "9e-05"},
+    {0.00009f, chars_format::general, 3, "9e-05"},
+    {0.00009f, chars_format::general, 4, "9e-05"},
+    {0.00009f, chars_format::general, 5, "9e-05"},
+    {0.00009f, chars_format::general, 6, "9e-05"},
+
+    // Rounding test cases without exponent-adjusting behavior.
+    {2999.999f, chars_format::general, 1, "3e+03"},
+    {2999.999f, chars_format::general, 2, "3e+03"},
+    {2999.999f, chars_format::general, 3, "3e+03"},
+    {2999.999f, chars_format::general, 4, "3000"},
+    {2999.999f, chars_format::general, 5, "3000"},
+    {2999.999f, chars_format::general, 6, "3000"},
+
+    {2999.99f, chars_format::general, 1, "3e+03"},
+    {2999.99f, chars_format::general, 2, "3e+03"},
+    {2999.99f, chars_format::general, 3, "3e+03"},
+    {2999.99f, chars_format::general, 4, "3000"},
+    {2999.99f, chars_format::general, 5, "3000"},
+    {2999.99f, chars_format::general, 6, "2999.99"},
+
+    {2999.9f, chars_format::general, 1, "3e+03"},
+    {2999.9f, chars_format::general, 2, "3e+03"},
+    {2999.9f, chars_format::general, 3, "3e+03"},
+    {2999.9f, chars_format::general, 4, "3000"},
+    {2999.9f, chars_format::general, 5, "2999.9"},
+    {2999.9f, chars_format::general, 6, "2999.9"},
+
+    {2999.0f, chars_format::general, 1, "3e+03"},
+    {2999.0f, chars_format::general, 2, "3e+03"},
+    {2999.0f, chars_format::general, 3, "3e+03"},
+    {2999.0f, chars_format::general, 4, "2999"},
+    {2999.0f, chars_format::general, 5, "2999"},
+    {2999.0f, chars_format::general, 6, "2999"},
+
+    {299.999f, chars_format::general, 1, "3e+02"},
+    {299.999f, chars_format::general, 2, "3e+02"},
+    {299.999f, chars_format::general, 3, "300"},
+    {299.999f, chars_format::general, 4, "300"},
+    {299.999f, chars_format::general, 5, "300"},
+    {299.999f, chars_format::general, 6, "299.999"},
+
+    {299.99f, chars_format::general, 1, "3e+02"},
+    {299.99f, chars_format::general, 2, "3e+02"},
+    {299.99f, chars_format::general, 3, "300"},
+    {299.99f, chars_format::general, 4, "300"},
+    {299.99f, chars_format::general, 5, "299.99"},
+    {299.99f, chars_format::general, 6, "299.99"},
+
+    {299.9f, chars_format::general, 1, "3e+02"},
+    {299.9f, chars_format::general, 2, "3e+02"},
+    {299.9f, chars_format::general, 3, "300"},
+    {299.9f, chars_format::general, 4, "299.9"},
+    {299.9f, chars_format::general, 5, "299.9"},
+    {299.9f, chars_format::general, 6, "299.9"},
+
+    {299.0f, chars_format::general, 1, "3e+02"},
+    {299.0f, chars_format::general, 2, "3e+02"},
+    {299.0f, chars_format::general, 3, "299"},
+    {299.0f, chars_format::general, 4, "299"},
+    {299.0f, chars_format::general, 5, "299"},
+    {299.0f, chars_format::general, 6, "299"},
+
+    {29.999f, chars_format::general, 1, "3e+01"},
+    {29.999f, chars_format::general, 2, "30"},
+    {29.999f, chars_format::general, 3, "30"},
+    {29.999f, chars_format::general, 4, "30"},
+    {29.999f, chars_format::general, 5, "29.999"},
+    {29.999f, chars_format::general, 6, "29.999"},
+
+    {29.99f, chars_format::general, 1, "3e+01"},
+    {29.99f, chars_format::general, 2, "30"},
+    {29.99f, chars_format::general, 3, "30"},
+    {29.99f, chars_format::general, 4, "29.99"},
+    {29.99f, chars_format::general, 5, "29.99"},
+    {29.99f, chars_format::general, 6, "29.99"},
+
+    {29.9f, chars_format::general, 1, "3e+01"},
+    {29.9f, chars_format::general, 2, "30"},
+    {29.9f, chars_format::general, 3, "29.9"},
+    {29.9f, chars_format::general, 4, "29.9"},
+    {29.9f, chars_format::general, 5, "29.9"},
+    {29.9f, chars_format::general, 6, "29.9"},
+
+    {29.0f, chars_format::general, 1, "3e+01"},
+    {29.0f, chars_format::general, 2, "29"},
+    {29.0f, chars_format::general, 3, "29"},
+    {29.0f, chars_format::general, 4, "29"},
+    {29.0f, chars_format::general, 5, "29"},
+    {29.0f, chars_format::general, 6, "29"},
+
+    {2.999f, chars_format::general, 1, "3"},
+    {2.999f, chars_format::general, 2, "3"},
+    {2.999f, chars_format::general, 3, "3"},
+    {2.999f, chars_format::general, 4, "2.999"},
+    {2.999f, chars_format::general, 5, "2.999"},
+    {2.999f, chars_format::general, 6, "2.999"},
+
+    {2.99f, chars_format::general, 1, "3"},
+    {2.99f, chars_format::general, 2, "3"},
+    {2.99f, chars_format::general, 3, "2.99"},
+    {2.99f, chars_format::general, 4, "2.99"},
+    {2.99f, chars_format::general, 5, "2.99"},
+    {2.99f, chars_format::general, 6, "2.99"},
+
+    {2.9f, chars_format::general, 1, "3"},
+    {2.9f, chars_format::general, 2, "2.9"},
+    {2.9f, chars_format::general, 3, "2.9"},
+    {2.9f, chars_format::general, 4, "2.9"},
+    {2.9f, chars_format::general, 5, "2.9"},
+    {2.9f, chars_format::general, 6, "2.9"},
+
+    {2.0f, chars_format::general, 1, "2"},
+    {2.0f, chars_format::general, 2, "2"},
+    {2.0f, chars_format::general, 3, "2"},
+    {2.0f, chars_format::general, 4, "2"},
+    {2.0f, chars_format::general, 5, "2"},
+    {2.0f, chars_format::general, 6, "2"},
+
+    {0.2999f, chars_format::general, 1, "0.3"},
+    {0.2999f, chars_format::general, 2, "0.3"},
+    {0.2999f, chars_format::general, 3, "0.3"},
+    {0.2999f, chars_format::general, 4, "0.2999"},
+    {0.2999f, chars_format::general, 5, "0.2999"},
+    {0.2999f, chars_format::general, 6, "0.2999"},
+
+    {0.299f, chars_format::general, 1, "0.3"},
+    {0.299f, chars_format::general, 2, "0.3"},
+    {0.299f, chars_format::general, 3, "0.299"},
+    {0.299f, chars_format::general, 4, "0.299"},
+    {0.299f, chars_format::general, 5, "0.299"},
+    {0.299f, chars_format::general, 6, "0.299"},
+
+    {0.29f, chars_format::general, 1, "0.3"},
+    {0.29f, chars_format::general, 2, "0.29"},
+    {0.29f, chars_format::general, 3, "0.29"},
+    {0.29f, chars_format::general, 4, "0.29"},
+    {0.29f, chars_format::general, 5, "0.29"},
+    {0.29f, chars_format::general, 6, "0.29"},
+
+    {0.2f, chars_format::general, 1, "0.2"},
+    {0.2f, chars_format::general, 2, "0.2"},
+    {0.2f, chars_format::general, 3, "0.2"},
+    {0.2f, chars_format::general, 4, "0.2"},
+    {0.2f, chars_format::general, 5, "0.2"},
+    {0.2f, chars_format::general, 6, "0.2"},
+
+    {0.02999f, chars_format::general, 1, "0.03"},
+    {0.02999f, chars_format::general, 2, "0.03"},
+    {0.02999f, chars_format::general, 3, "0.03"},
+    {0.02999f, chars_format::general, 4, "0.02999"},
+    {0.02999f, chars_format::general, 5, "0.02999"},
+    {0.02999f, chars_format::general, 6, "0.02999"},
+
+    {0.0299f, chars_format::general, 1, "0.03"},
+    {0.0299f, chars_format::general, 2, "0.03"},
+    {0.0299f, chars_format::general, 3, "0.0299"},
+    {0.0299f, chars_format::general, 4, "0.0299"},
+    {0.0299f, chars_format::general, 5, "0.0299"},
+    {0.0299f, chars_format::general, 6, "0.0299"},
+
+    {0.029f, chars_format::general, 1, "0.03"},
+    {0.029f, chars_format::general, 2, "0.029"},
+    {0.029f, chars_format::general, 3, "0.029"},
+    {0.029f, chars_format::general, 4, "0.029"},
+    {0.029f, chars_format::general, 5, "0.029"},
+    {0.029f, chars_format::general, 6, "0.029"},
+
+    {0.02f, chars_format::general, 1, "0.02"},
+    {0.02f, chars_format::general, 2, "0.02"},
+    {0.02f, chars_format::general, 3, "0.02"},
+    {0.02f, chars_format::general, 4, "0.02"},
+    {0.02f, chars_format::general, 5, "0.02"},
+    {0.02f, chars_format::general, 6, "0.02"},
+
+    {0.002999f, chars_format::general, 1, "0.003"},
+    {0.002999f, chars_format::general, 2, "0.003"},
+    {0.002999f, chars_format::general, 3, "0.003"},
+    {0.002999f, chars_format::general, 4, "0.002999"},
+    {0.002999f, chars_format::general, 5, "0.002999"},
+    {0.002999f, chars_format::general, 6, "0.002999"},
+
+    {0.00299f, chars_format::general, 1, "0.003"},
+    {0.00299f, chars_format::general, 2, "0.003"},
+    {0.00299f, chars_format::general, 3, "0.00299"},
+    {0.00299f, chars_format::general, 4, "0.00299"},
+    {0.00299f, chars_format::general, 5, "0.00299"},
+    {0.00299f, chars_format::general, 6, "0.00299"},
+
+    {0.0029f, chars_format::general, 1, "0.003"},
+    {0.0029f, chars_format::general, 2, "0.0029"},
+    {0.0029f, chars_format::general, 3, "0.0029"},
+    {0.0029f, chars_format::general, 4, "0.0029"},
+    {0.0029f, chars_format::general, 5, "0.0029"},
+    {0.0029f, chars_format::general, 6, "0.0029"},
+
+    {0.002f, chars_format::general, 1, "0.002"},
+    {0.002f, chars_format::general, 2, "0.002"},
+    {0.002f, chars_format::general, 3, "0.002"},
+    {0.002f, chars_format::general, 4, "0.002"},
+    {0.002f, chars_format::general, 5, "0.002"},
+    {0.002f, chars_format::general, 6, "0.002"},
+
+    {0.0002999f, chars_format::general, 1, "0.0003"},
+    {0.0002999f, chars_format::general, 2, "0.0003"},
+    {0.0002999f, chars_format::general, 3, "0.0003"},
+    {0.0002999f, chars_format::general, 4, "0.0002999"},
+    {0.0002999f, chars_format::general, 5, "0.0002999"},
+    {0.0002999f, chars_format::general, 6, "0.0002999"},
+
+    {0.000299f, chars_format::general, 1, "0.0003"},
+    {0.000299f, chars_format::general, 2, "0.0003"},
+    {0.000299f, chars_format::general, 3, "0.000299"},
+    {0.000299f, chars_format::general, 4, "0.000299"},
+    {0.000299f, chars_format::general, 5, "0.000299"},
+    {0.000299f, chars_format::general, 6, "0.000299"},
+
+    {0.00029f, chars_format::general, 1, "0.0003"},
+    {0.00029f, chars_format::general, 2, "0.00029"},
+    {0.00029f, chars_format::general, 3, "0.00029"},
+    {0.00029f, chars_format::general, 4, "0.00029"},
+    {0.00029f, chars_format::general, 5, "0.00029"},
+    {0.00029f, chars_format::general, 6, "0.00029"},
+
+    {0.0002f, chars_format::general, 1, "0.0002"},
+    {0.0002f, chars_format::general, 2, "0.0002"},
+    {0.0002f, chars_format::general, 3, "0.0002"},
+    {0.0002f, chars_format::general, 4, "0.0002"},
+    {0.0002f, chars_format::general, 5, "0.0002"},
+    {0.0002f, chars_format::general, 6, "0.0002"},
+
+    {0.00002999f, chars_format::general, 1, "3e-05"},
+    {0.00002999f, chars_format::general, 2, "3e-05"},
+    {0.00002999f, chars_format::general, 3, "3e-05"},
+    {0.00002999f, chars_format::general, 4, "2.999e-05"},
+    {0.00002999f, chars_format::general, 5, "2.999e-05"},
+    {0.00002999f, chars_format::general, 6, "2.999e-05"},
+
+    {0.0000299f, chars_format::general, 1, "3e-05"},
+    {0.0000299f, chars_format::general, 2, "3e-05"},
+    {0.0000299f, chars_format::general, 3, "2.99e-05"},
+    {0.0000299f, chars_format::general, 4, "2.99e-05"},
+    {0.0000299f, chars_format::general, 5, "2.99e-05"},
+    {0.0000299f, chars_format::general, 6, "2.99e-05"},
+
+    {0.000029f, chars_format::general, 1, "3e-05"},
+    {0.000029f, chars_format::general, 2, "2.9e-05"},
+    {0.000029f, chars_format::general, 3, "2.9e-05"},
+    {0.000029f, chars_format::general, 4, "2.9e-05"},
+    {0.000029f, chars_format::general, 5, "2.9e-05"},
+    {0.000029f, chars_format::general, 6, "2.9e-05"},
+
+    {0.00002f, chars_format::general, 1, "2e-05"},
+    {0.00002f, chars_format::general, 2, "2e-05"},
+    {0.00002f, chars_format::general, 3, "2e-05"},
+    {0.00002f, chars_format::general, 4, "2e-05"},
+    {0.00002f, chars_format::general, 5, "2e-05"},
+    {0.00002f, chars_format::general, 6, "2e-05"},
+
+    // Test the transitions between values of the scientific exponent X.
+    // For brevity, we avoid testing all possible combinations of P and X. Instead, we test:
+    // * All values of P where some X can be affected by rounding. (For float, this is [1, 7].)
+    // * P == 25, which is arbitrary.
+    // * P == numeric_limits::max_exponent10 + 1. This selects fixed notation for numeric_limits::max(),
+    //   so it's the largest interesting value of P.
+    // * Finally, we test the transitions around X == P - 1, ensuring that we can recognize every value of X.
+    {0x1.8e7578p-14f, chars_format::general, 1, "9e-05"},
+    {0x1.8e757ap-14f, chars_format::general, 1, "0.0001"},
+    {0x1.f212d6p-11f, chars_format::general, 1, "0.0009"},
+    {0x1.f212d8p-11f, chars_format::general, 1, "0.001"},
+    {0x1.374bc6p-7f, chars_format::general, 1, "0.009"},
+    {0x1.374bc8p-7f, chars_format::general, 1, "0.01"},
+    {0x1.851eb8p-4f, chars_format::general, 1, "0.09"},
+    {0x1.851ebap-4f, chars_format::general, 1, "0.1"},
+    {0x1.e66666p-1f, chars_format::general, 1, "0.9"},
+    {0x1.e66668p-1f, chars_format::general, 1, "1"},
+    {0x1.2ffffep+3f, chars_format::general, 1, "9"},
+    {0x1.300000p+3f, chars_format::general, 1, "1e+01"},
+    {0x1.a1554ep-14f, chars_format::general, 2, "9.9e-05"},
+    {0x1.a15550p-14f, chars_format::general, 2, "0.0001"},
+    {0x1.04d550p-10f, chars_format::general, 2, "0.00099"},
+    {0x1.04d552p-10f, chars_format::general, 2, "0.001"},
+    {0x1.460aa6p-7f, chars_format::general, 2, "0.0099"},
+    {0x1.460aa8p-7f, chars_format::general, 2, "0.01"},
+    {0x1.978d4ep-4f, chars_format::general, 2, "0.099"},
+    {0x1.978d50p-4f, chars_format::general, 2, "0.1"},
+    {0x1.fd70a2p-1f, chars_format::general, 2, "0.99"},
+    {0x1.fd70a4p-1f, chars_format::general, 2, "1"},
+    {0x1.3e6666p+3f, chars_format::general, 2, "9.9"},
+    {0x1.3e6668p+3f, chars_format::general, 2, "10"},
+    {0x1.8dfffep+6f, chars_format::general, 2, "99"},
+    {0x1.8e0000p+6f, chars_format::general, 2, "1e+02"},
+    {0x1.a3387ep-14f, chars_format::general, 3, "9.99e-05"},
+    {0x1.a33880p-14f, chars_format::general, 3, "0.0001"},
+    {0x1.06034ep-10f, chars_format::general, 3, "0.000999"},
+    {0x1.060350p-10f, chars_format::general, 3, "0.001"},
+    {0x1.478422p-7f, chars_format::general, 3, "0.00999"},
+    {0x1.478424p-7f, chars_format::general, 3, "0.01"},
+    {0x1.99652ap-4f, chars_format::general, 3, "0.0999"},
+    {0x1.99652cp-4f, chars_format::general, 3, "0.1"},
+    {0x1.ffbe76p-1f, chars_format::general, 3, "0.999"},
+    {0x1.ffbe78p-1f, chars_format::general, 3, "1"},
+    {0x1.3fd70ap+3f, chars_format::general, 3, "9.99"},
+    {0x1.3fd70cp+3f, chars_format::general, 3, "10"},
+    {0x1.8fccccp+6f, chars_format::general, 3, "99.9"},
+    {0x1.8fcccep+6f, chars_format::general, 3, "100"},
+    {0x1.f3bffep+9f, chars_format::general, 3, "999"},
+    {0x1.f3c000p+9f, chars_format::general, 3, "1e+03"},
+    {0x1.a368d0p-14f, chars_format::general, 4, "9.999e-05"},
+    {0x1.a368d2p-14f, chars_format::general, 4, "0.0001"},
+    {0x1.062182p-10f, chars_format::general, 4, "0.0009999"},
+    {0x1.062184p-10f, chars_format::general, 4, "0.001"},
+    {0x1.47a9e2p-7f, chars_format::general, 4, "0.009999"},
+    {0x1.47a9e4p-7f, chars_format::general, 4, "0.01"},
+    {0x1.99945ap-4f, chars_format::general, 4, "0.09999"},
+    {0x1.99945cp-4f, chars_format::general, 4, "0.1"},
+    {0x1.fff972p-1f, chars_format::general, 4, "0.9999"},
+    {0x1.fff974p-1f, chars_format::general, 4, "1"},
+    {0x1.3ffbe6p+3f, chars_format::general, 4, "9.999"},
+    {0x1.3ffbe8p+3f, chars_format::general, 4, "10"},
+    {0x1.8ffae0p+6f, chars_format::general, 4, "99.99"},
+    {0x1.8ffae2p+6f, chars_format::general, 4, "100"},
+    {0x1.f3f998p+9f, chars_format::general, 4, "999.9"},
+    {0x1.f3f99ap+9f, chars_format::general, 4, "1000"},
+    {0x1.387bfep+13f, chars_format::general, 4, "9999"},
+    {0x1.387c00p+13f, chars_format::general, 4, "1e+04"},
+    {0x1.a36da4p-14f, chars_format::general, 5, "9.9999e-05"},
+    {0x1.a36da6p-14f, chars_format::general, 5, "0.0001"},
+    {0x1.062486p-10f, chars_format::general, 5, "0.00099999"},
+    {0x1.062488p-10f, chars_format::general, 5, "0.001"},
+    {0x1.47ada8p-7f, chars_format::general, 5, "0.0099999"},
+    {0x1.47adaap-7f, chars_format::general, 5, "0.01"},
+    {0x1.999912p-4f, chars_format::general, 5, "0.099999"},
+    {0x1.999914p-4f, chars_format::general, 5, "0.1"},
+    {0x1.ffff58p-1f, chars_format::general, 5, "0.99999"},
+    {0x1.ffff5ap-1f, chars_format::general, 5, "1"},
+    {0x1.3fff96p+3f, chars_format::general, 5, "9.9999"},
+    {0x1.3fff98p+3f, chars_format::general, 5, "10"},
+    {0x1.8fff7cp+6f, chars_format::general, 5, "99.999"},
+    {0x1.8fff7ep+6f, chars_format::general, 5, "100"},
+    {0x1.f3ff5cp+9f, chars_format::general, 5, "999.99"},
+    {0x1.f3ff5ep+9f, chars_format::general, 5, "1000"},
+    {0x1.387f98p+13f, chars_format::general, 5, "9999.9"},
+    {0x1.387f9ap+13f, chars_format::general, 5, "10000"},
+    {0x1.869f7ep+16f, chars_format::general, 5, "99999"},
+    {0x1.869f80p+16f, chars_format::general, 5, "1e+05"},
+    {0x1.a36e20p-14f, chars_format::general, 6, "9.99999e-05"},
+    {0x1.a36e22p-14f, chars_format::general, 6, "0.0001"},
+    {0x1.0624d4p-10f, chars_format::general, 6, "0.000999999"},
+    {0x1.0624d6p-10f, chars_format::general, 6, "0.001"},
+    {0x1.47ae08p-7f, chars_format::general, 6, "0.00999999"},
+    {0x1.47ae0ap-7f, chars_format::general, 6, "0.01"},
+    {0x1.99998cp-4f, chars_format::general, 6, "0.0999999"},
+    {0x1.99998ep-4f, chars_format::general, 6, "0.1"},
+    {0x1.ffffeep-1f, chars_format::general, 6, "0.999999"},
+    {0x1.fffff0p-1f, chars_format::general, 6, "1"},
+    {0x1.3ffff4p+3f, chars_format::general, 6, "9.99999"},
+    {0x1.3ffff6p+3f, chars_format::general, 6, "10"},
+    {0x1.8ffff2p+6f, chars_format::general, 6, "99.9999"},
+    {0x1.8ffff4p+6f, chars_format::general, 6, "100"},
+    {0x1.f3ffeep+9f, chars_format::general, 6, "999.999"},
+    {0x1.f3fff0p+9f, chars_format::general, 6, "1000"},
+    {0x1.387ff4p+13f, chars_format::general, 6, "9999.99"},
+    {0x1.387ff6p+13f, chars_format::general, 6, "10000"},
+    {0x1.869ff2p+16f, chars_format::general, 6, "99999.9"},
+    {0x1.869ff4p+16f, chars_format::general, 6, "100000"},
+    {0x1.e847eep+19f, chars_format::general, 6, "999999"},
+    {0x1.e847f0p+19f, chars_format::general, 6, "1e+06"},
+    {0x1.a36e2cp-14f, chars_format::general, 7, "9.999999e-05"},
+    {0x1.a36e2ep-14f, chars_format::general, 7, "0.0001"},
+    {0x1.0624dcp-10f, chars_format::general, 7, "0.0009999999"},
+    {0x1.0624dep-10f, chars_format::general, 7, "0.001"},
+    {0x1.47ae12p-7f, chars_format::general, 7, "0.009999999"},
+    {0x1.47ae14p-7f, chars_format::general, 7, "0.01"},
+    {0x1.999998p-4f, chars_format::general, 7, "0.09999999"},
+    {0x1.99999ap-4f, chars_format::general, 7, "0.1"},
+    {0x1.fffffep-1f, chars_format::general, 7, "0.9999999"},
+    {0x1.000000p+0f, chars_format::general, 7, "1"},
+    {0x1.3ffffep+3f, chars_format::general, 7, "9.999999"},
+    {0x1.400000p+3f, chars_format::general, 7, "10"},
+    {0x1.8ffffep+6f, chars_format::general, 7, "99.99999"},
+    {0x1.900000p+6f, chars_format::general, 7, "100"},
+    {0x1.f3fffep+9f, chars_format::general, 7, "999.9999"},
+    {0x1.f40000p+9f, chars_format::general, 7, "1000"},
+    {0x1.387ffep+13f, chars_format::general, 7, "9999.999"},
+    {0x1.388000p+13f, chars_format::general, 7, "10000"},
+    {0x1.869ffep+16f, chars_format::general, 7, "99999.99"},
+    {0x1.86a000p+16f, chars_format::general, 7, "100000"},
+    {0x1.e847fep+19f, chars_format::general, 7, "999999.9"},
+    {0x1.e84800p+19f, chars_format::general, 7, "1000000"},
+    {0x1.312cfep+23f, chars_format::general, 7, "9999999"},
+    {0x1.312d00p+23f, chars_format::general, 7, "1e+07"},
+    {0x1.7d783ep+26f, chars_format::general, 8, "99999992"},
+    {0x1.7d7840p+26f, chars_format::general, 8, "1e+08"},
+    {0x1.dcd64ep+29f, chars_format::general, 9, "999999936"},
+    {0x1.dcd650p+29f, chars_format::general, 9, "1e+09"},
+    {0x1.2a05f0p+33f, chars_format::general, 10, "9999998976"},
+    {0x1.2a05f2p+33f, chars_format::general, 10, "1e+10"},
+    {0x1.74876ep+36f, chars_format::general, 11, "99999997952"},
+    {0x1.748770p+36f, chars_format::general, 11, "1.0000000614e+11"},
+    {0x1.d1a94ap+39f, chars_format::general, 12, "999999995904"},
+    {0x1.d1a94cp+39f, chars_format::general, 12, "1.00000006144e+12"},
+    {0x1.2309cep+43f, chars_format::general, 13, "9999999827968"},
+    {0x1.2309d0p+43f, chars_format::general, 13, "1.000000087654e+13"},
+    {0x1.6bcc40p+46f, chars_format::general, 14, "99999991988224"},
+    {0x1.6bcc42p+46f, chars_format::general, 14, "1.0000000037683e+14"},
+    {0x1.c6bf52p+49f, chars_format::general, 15, "999999986991104"},
+    {0x1.c6bf54p+49f, chars_format::general, 15, "1.00000005409997e+15"},
+    {0x1.1c3792p+53f, chars_format::general, 16, "9999999198822400"},
+    {0x1.1c3794p+53f, chars_format::general, 16, "1.000000027256422e+16"},
+    {0x1.634578p+56f, chars_format::general, 17, "99999998430674944"},
+    {0x1.63457ap+56f, chars_format::general, 17, "1.0000000702060954e+17"},
+    {0x1.bc16d6p+59f, chars_format::general, 18, "999999984306749440"},
+    {0x1.bc16d8p+59f, chars_format::general, 18, "1.00000005302622618e+18"},
+    {0x1.158e46p+63f, chars_format::general, 19, "9999999980506447872"},
+    {0x1.158e48p+63f, chars_format::general, 19, "1.000000108001807565e+19"},
+    {0x1.5af1d6p+66f, chars_format::general, 20, "99999993207994712064"},
+    {0x1.5af1d8p+66f, chars_format::general, 20, "1.0000000200408773427e+20"},
+    {0x1.b1ae4cp+69f, chars_format::general, 21, "999999949672133165056"},
+    {0x1.b1ae4ep+69f, chars_format::general, 21, "1.00000002004087734272e+21"},
+    {0x1.0f0cf0p+73f, chars_format::general, 22, "9999999778196308361216"},
+    {0x1.0f0cf2p+73f, chars_format::general, 22, "1.000000090409621520384e+22"},
+    {0x1.52d02cp+76f, chars_format::general, 23, "99999997781963083612160"},
+    {0x1.52d02ep+76f, chars_format::general, 23, "1.0000000678916233835315e+23"},
+    {0x1.a78436p+79f, chars_format::general, 24, "999999941790833817157632"},
+    {0x1.a78438p+79f, chars_format::general, 24, "1.00000001384842785508557e+24"},
+    {0x1.a36e2ep-14f, chars_format::general, 25, "9.999999747378751635551453e-05"},
+    {0x1.a36e30p-14f, chars_format::general, 25, "0.0001000000047497451305389404"},
+    {0x1.0624dcp-10f, chars_format::general, 25, "0.0009999999310821294784545898"},
+    {0x1.0624dep-10f, chars_format::general, 25, "0.001000000047497451305389404"},
+    {0x1.47ae14p-7f, chars_format::general, 25, "0.009999999776482582092285156"},
+    {0x1.47ae16p-7f, chars_format::general, 25, "0.01000000070780515670776367"},
+    {0x1.999998p-4f, chars_format::general, 25, "0.0999999940395355224609375"},
+    {0x1.99999ap-4f, chars_format::general, 25, "0.1000000014901161193847656"},
+    {0x1.fffffep-1f, chars_format::general, 25, "0.999999940395355224609375"},
+    {0x1.000000p+0f, chars_format::general, 25, "1"},
+    {0x1.3ffffep+3f, chars_format::general, 25, "9.99999904632568359375"},
+    {0x1.400000p+3f, chars_format::general, 25, "10"},
+    {0x1.8ffffep+6f, chars_format::general, 25, "99.99999237060546875"},
+    {0x1.900000p+6f, chars_format::general, 25, "100"},
+    {0x1.f3fffep+9f, chars_format::general, 25, "999.99993896484375"},
+    {0x1.f40000p+9f, chars_format::general, 25, "1000"},
+    {0x1.387ffep+13f, chars_format::general, 25, "9999.9990234375"},
+    {0x1.388000p+13f, chars_format::general, 25, "10000"},
+    {0x1.869ffep+16f, chars_format::general, 25, "99999.9921875"},
+    {0x1.86a000p+16f, chars_format::general, 25, "100000"},
+    {0x1.e847fep+19f, chars_format::general, 25, "999999.9375"},
+    {0x1.e84800p+19f, chars_format::general, 25, "1000000"},
+    {0x1.312cfep+23f, chars_format::general, 25, "9999999"},
+    {0x1.312d00p+23f, chars_format::general, 25, "10000000"},
+    {0x1.7d783ep+26f, chars_format::general, 25, "99999992"},
+    {0x1.7d7840p+26f, chars_format::general, 25, "100000000"},
+    {0x1.dcd64ep+29f, chars_format::general, 25, "999999936"},
+    {0x1.dcd650p+29f, chars_format::general, 25, "1000000000"},
+    {0x1.2a05f0p+33f, chars_format::general, 25, "9999998976"},
+    {0x1.2a05f2p+33f, chars_format::general, 25, "10000000000"},
+    {0x1.74876ep+36f, chars_format::general, 25, "99999997952"},
+    {0x1.748770p+36f, chars_format::general, 25, "100000006144"},
+    {0x1.d1a94ap+39f, chars_format::general, 25, "999999995904"},
+    {0x1.d1a94cp+39f, chars_format::general, 25, "1000000061440"},
+    {0x1.2309cep+43f, chars_format::general, 25, "9999999827968"},
+    {0x1.2309d0p+43f, chars_format::general, 25, "10000000876544"},
+    {0x1.6bcc40p+46f, chars_format::general, 25, "99999991988224"},
+    {0x1.6bcc42p+46f, chars_format::general, 25, "100000000376832"},
+    {0x1.c6bf52p+49f, chars_format::general, 25, "999999986991104"},
+    {0x1.c6bf54p+49f, chars_format::general, 25, "1000000054099968"},
+    {0x1.1c3792p+53f, chars_format::general, 25, "9999999198822400"},
+    {0x1.1c3794p+53f, chars_format::general, 25, "10000000272564224"},
+    {0x1.634578p+56f, chars_format::general, 25, "99999998430674944"},
+    {0x1.63457ap+56f, chars_format::general, 25, "100000007020609536"},
+    {0x1.bc16d6p+59f, chars_format::general, 25, "999999984306749440"},
+    {0x1.bc16d8p+59f, chars_format::general, 25, "1000000053026226176"},
+    {0x1.158e46p+63f, chars_format::general, 25, "9999999980506447872"},
+    {0x1.158e48p+63f, chars_format::general, 25, "10000001080018075648"},
+    {0x1.5af1d6p+66f, chars_format::general, 25, "99999993207994712064"},
+    {0x1.5af1d8p+66f, chars_format::general, 25, "100000002004087734272"},
+    {0x1.b1ae4cp+69f, chars_format::general, 25, "999999949672133165056"},
+    {0x1.b1ae4ep+69f, chars_format::general, 25, "1000000020040877342720"},
+    {0x1.0f0cf0p+73f, chars_format::general, 25, "9999999778196308361216"},
+    {0x1.0f0cf2p+73f, chars_format::general, 25, "10000000904096215203840"},
+    {0x1.52d02cp+76f, chars_format::general, 25, "99999997781963083612160"},
+    {0x1.52d02ep+76f, chars_format::general, 25, "100000006789162338353152"},
+    {0x1.a78436p+79f, chars_format::general, 25, "999999941790833817157632"},
+    {0x1.a78438p+79f, chars_format::general, 25, "1000000013848427855085568"},
+    {0x1.08b2a2p+83f, chars_format::general, 25, "9999999562023526247432192"},
+    {0x1.08b2a4p+83f, chars_format::general, 25, "1.000000071494503085427917e+25"},
+    {0x1.4adf4ap+86f, chars_format::general, 26, "99999993314392253260627968"},
+    {0x1.4adf4cp+86f, chars_format::general, 26, "1.0000000253776429011540378e+26"},
+    {0x1.9d971ep+89f, chars_format::general, 27, "999999988484154753734934528"},
+    {0x1.9d9720p+89f, chars_format::general, 27, "1.00000006227113104857314099e+27"},
+    {0x1.027e72p+93f, chars_format::general, 28, "9999999442119689768320106496"},
+    {0x1.027e74p+93f, chars_format::general, 28, "1.000000062271131048573140992e+28"},
+    {0x1.431e0ep+96f, chars_format::general, 29, "99999992060013656248378458112"},
+    {0x1.431e10p+96f, chars_format::general, 29, "1.000000015047466219876688855e+29"},
+    {0x1.93e592p+99f, chars_format::general, 30, "999999939489602493962365435904"},
+    {0x1.93e594p+99f, chars_format::general, 30, "1.00000001504746621987668885504e+30"},
+    {0x1.f8def8p+102f, chars_format::general, 31, "9999999848243207295109594873856"},
+    {0x1.f8defap+102f, chars_format::general, 31, "1.000000045270611710242418222694e+31"},
+    {0x1.3b8b5ap+106f, chars_format::general, 32, "99999993646728794492579249913856"},
+    {0x1.3b8b5cp+106f, chars_format::general, 32, "1.0000000331813535140961264756326e+32"},
+    {0x1.8a6e32p+109f, chars_format::general, 33, "999999994495727286427992885035008"},
+    {0x1.8a6e34p+109f, chars_format::general, 33, "1.00000007186697974176426006623027e+33"},
+    {0x1.ed09bep+112f, chars_format::general, 34, "9999999790214767953607394487959552"},
+    {0x1.ed09c0p+112f, chars_format::general, 34, "1.000000040918478759629753193752166e+34"},
+    {0x1.342616p+116f, chars_format::general, 35, "99999994188327561679933120182222848"},
+    {0x1.342618p+116f, chars_format::general, 35, "1.0000000409184787596297531937521664e+35"},
+    {0x1.812f9cp+119f, chars_format::general, 36, "999999961690316245365415600208216064"},
+    {0x1.812f9ep+119f, chars_format::general, 36, "1.0000000409184787596297531937521664e+36"},
+    {0x1.e17b84p+122f, chars_format::general, 37, "9999999933815812510711506376257961984"},
+    {0x1.e17b86p+122f, chars_format::general, 37, "1.000000056764111262482620712460956467e+37"},
+    {0x1.2ced32p+126f, chars_format::general, 38, "99999996802856924650656260769173209088"},
+    {0x1.2ced34p+126f, chars_format::general, 38, "1.000000069440617264764914727427988521e+38"},
+    {0x1.a36e2ep-14f, chars_format::general, 39, "9.99999974737875163555145263671875e-05"},
+    {0x1.a36e30p-14f, chars_format::general, 39, "0.0001000000047497451305389404296875"},
+    {0x1.0624dcp-10f, chars_format::general, 39, "0.00099999993108212947845458984375"},
+    {0x1.0624dep-10f, chars_format::general, 39, "0.001000000047497451305389404296875"},
+    {0x1.47ae14p-7f, chars_format::general, 39, "0.00999999977648258209228515625"},
+    {0x1.47ae16p-7f, chars_format::general, 39, "0.010000000707805156707763671875"},
+    {0x1.999998p-4f, chars_format::general, 39, "0.0999999940395355224609375"},
+    {0x1.99999ap-4f, chars_format::general, 39, "0.100000001490116119384765625"},
+    {0x1.fffffep-1f, chars_format::general, 39, "0.999999940395355224609375"},
+    {0x1.000000p+0f, chars_format::general, 39, "1"},
+    {0x1.3ffffep+3f, chars_format::general, 39, "9.99999904632568359375"},
+    {0x1.400000p+3f, chars_format::general, 39, "10"},
+    {0x1.8ffffep+6f, chars_format::general, 39, "99.99999237060546875"},
+    {0x1.900000p+6f, chars_format::general, 39, "100"},
+    {0x1.f3fffep+9f, chars_format::general, 39, "999.99993896484375"},
+    {0x1.f40000p+9f, chars_format::general, 39, "1000"},
+    {0x1.387ffep+13f, chars_format::general, 39, "9999.9990234375"},
+    {0x1.388000p+13f, chars_format::general, 39, "10000"},
+    {0x1.869ffep+16f, chars_format::general, 39, "99999.9921875"},
+    {0x1.86a000p+16f, chars_format::general, 39, "100000"},
+    {0x1.e847fep+19f, chars_format::general, 39, "999999.9375"},
+    {0x1.e84800p+19f, chars_format::general, 39, "1000000"},
+    {0x1.312cfep+23f, chars_format::general, 39, "9999999"},
+    {0x1.312d00p+23f, chars_format::general, 39, "10000000"},
+    {0x1.7d783ep+26f, chars_format::general, 39, "99999992"},
+    {0x1.7d7840p+26f, chars_format::general, 39, "100000000"},
+    {0x1.dcd64ep+29f, chars_format::general, 39, "999999936"},
+    {0x1.dcd650p+29f, chars_format::general, 39, "1000000000"},
+    {0x1.2a05f0p+33f, chars_format::general, 39, "9999998976"},
+    {0x1.2a05f2p+33f, chars_format::general, 39, "10000000000"},
+    {0x1.74876ep+36f, chars_format::general, 39, "99999997952"},
+    {0x1.748770p+36f, chars_format::general, 39, "100000006144"},
+    {0x1.d1a94ap+39f, chars_format::general, 39, "999999995904"},
+    {0x1.d1a94cp+39f, chars_format::general, 39, "1000000061440"},
+    {0x1.2309cep+43f, chars_format::general, 39, "9999999827968"},
+    {0x1.2309d0p+43f, chars_format::general, 39, "10000000876544"},
+    {0x1.6bcc40p+46f, chars_format::general, 39, "99999991988224"},
+    {0x1.6bcc42p+46f, chars_format::general, 39, "100000000376832"},
+    {0x1.c6bf52p+49f, chars_format::general, 39, "999999986991104"},
+    {0x1.c6bf54p+49f, chars_format::general, 39, "1000000054099968"},
+    {0x1.1c3792p+53f, chars_format::general, 39, "9999999198822400"},
+    {0x1.1c3794p+53f, chars_format::general, 39, "10000000272564224"},
+    {0x1.634578p+56f, chars_format::general, 39, "99999998430674944"},
+    {0x1.63457ap+56f, chars_format::general, 39, "100000007020609536"},
+    {0x1.bc16d6p+59f, chars_format::general, 39, "999999984306749440"},
+    {0x1.bc16d8p+59f, chars_format::general, 39, "1000000053026226176"},
+    {0x1.158e46p+63f, chars_format::general, 39, "9999999980506447872"},
+    {0x1.158e48p+63f, chars_format::general, 39, "10000001080018075648"},
+    {0x1.5af1d6p+66f, chars_format::general, 39, "99999993207994712064"},
+    {0x1.5af1d8p+66f, chars_format::general, 39, "100000002004087734272"},
+    {0x1.b1ae4cp+69f, chars_format::general, 39, "999999949672133165056"},
+    {0x1.b1ae4ep+69f, chars_format::general, 39, "1000000020040877342720"},
+    {0x1.0f0cf0p+73f, chars_format::general, 39, "9999999778196308361216"},
+    {0x1.0f0cf2p+73f, chars_format::general, 39, "10000000904096215203840"},
+    {0x1.52d02cp+76f, chars_format::general, 39, "99999997781963083612160"},
+    {0x1.52d02ep+76f, chars_format::general, 39, "100000006789162338353152"},
+    {0x1.a78436p+79f, chars_format::general, 39, "999999941790833817157632"},
+    {0x1.a78438p+79f, chars_format::general, 39, "1000000013848427855085568"},
+    {0x1.08b2a2p+83f, chars_format::general, 39, "9999999562023526247432192"},
+    {0x1.08b2a4p+83f, chars_format::general, 39, "10000000714945030854279168"},
+    {0x1.4adf4ap+86f, chars_format::general, 39, "99999993314392253260627968"},
+    {0x1.4adf4cp+86f, chars_format::general, 39, "100000002537764290115403776"},
+    {0x1.9d971ep+89f, chars_format::general, 39, "999999988484154753734934528"},
+    {0x1.9d9720p+89f, chars_format::general, 39, "1000000062271131048573140992"},
+    {0x1.027e72p+93f, chars_format::general, 39, "9999999442119689768320106496"},
+    {0x1.027e74p+93f, chars_format::general, 39, "10000000622711310485731409920"},
+    {0x1.431e0ep+96f, chars_format::general, 39, "99999992060013656248378458112"},
+    {0x1.431e10p+96f, chars_format::general, 39, "100000001504746621987668885504"},
+    {0x1.93e592p+99f, chars_format::general, 39, "999999939489602493962365435904"},
+    {0x1.93e594p+99f, chars_format::general, 39, "1000000015047466219876688855040"},
+    {0x1.f8def8p+102f, chars_format::general, 39, "9999999848243207295109594873856"},
+    {0x1.f8defap+102f, chars_format::general, 39, "10000000452706117102424182226944"},
+    {0x1.3b8b5ap+106f, chars_format::general, 39, "99999993646728794492579249913856"},
+    {0x1.3b8b5cp+106f, chars_format::general, 39, "100000003318135351409612647563264"},
+    {0x1.8a6e32p+109f, chars_format::general, 39, "999999994495727286427992885035008"},
+    {0x1.8a6e34p+109f, chars_format::general, 39, "1000000071866979741764260066230272"},
+    {0x1.ed09bep+112f, chars_format::general, 39, "9999999790214767953607394487959552"},
+    {0x1.ed09c0p+112f, chars_format::general, 39, "10000000409184787596297531937521664"},
+    {0x1.342616p+116f, chars_format::general, 39, "99999994188327561679933120182222848"},
+    {0x1.342618p+116f, chars_format::general, 39, "100000004091847875962975319375216640"},
+    {0x1.812f9cp+119f, chars_format::general, 39, "999999961690316245365415600208216064"},
+    {0x1.812f9ep+119f, chars_format::general, 39, "1000000040918478759629753193752166400"},
+    {0x1.e17b84p+122f, chars_format::general, 39, "9999999933815812510711506376257961984"},
+    {0x1.e17b86p+122f, chars_format::general, 39, "10000000567641112624826207124609564672"},
+    {0x1.2ced32p+126f, chars_format::general, 39, "99999996802856924650656260769173209088"},
+    {0x1.2ced34p+126f, chars_format::general, 39, "100000006944061726476491472742798852096"},
+    {0x1.fffffep+127f, chars_format::general, 39, "340282346638528859811704183484516925440"},
+};
+
+#endif // FLOAT_GENERAL_PRECISION_TO_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/float_hex_precision_to_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef FLOAT_HEX_PRECISION_TO_CHARS_TEST_CASES_HPP
+#define FLOAT_HEX_PRECISION_TO_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr FloatPrecisionToCharsTestCase float_hex_precision_to_chars_test_cases[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0f, chars_format::hex, 4, "0.0000p+0"},
+    {-0.0f, chars_format::hex, 4, "-0.0000p+0"},
+    {float_inf, chars_format::hex, 4, "inf"},
+    {-float_inf, chars_format::hex, 4, "-inf"},
+    {float_nan, chars_format::hex, 4, "nan"},
+    {-float_nan, chars_format::hex, 4, "-nan(ind)"},
+    {float_nan_payload, chars_format::hex, 4, "nan"},
+    {-float_nan_payload, chars_format::hex, 4, "-nan"},
+    {0x1.729p+0f, chars_format::hex, 4, "1.7290p+0"},
+    {-0x1.729p+0f, chars_format::hex, 4, "-1.7290p+0"},
+
+    // Test hexfloat corner cases.
+    {0x1.728p+0f, chars_format::hex, 6, "1.728000p+0"},
+    {0x0.000002p-126f, chars_format::hex, 6, "0.000002p-126"}, // min subnormal
+    {0x0.fffffep-126f, chars_format::hex, 6, "0.fffffep-126"}, // max subnormal
+    {0x1p-126f, chars_format::hex, 6, "1.000000p-126"}, // min normal
+    {0x1.fffffep+127f, chars_format::hex, 6, "1.fffffep+127"}, // max normal
+
+    // Test hexfloat exponents.
+    {0x1p-109f, chars_format::hex, 0, "1p-109"},
+    {0x1p-99f, chars_format::hex, 0, "1p-99"},
+    {0x1p-9f, chars_format::hex, 0, "1p-9"},
+    {0x1p+0f, chars_format::hex, 0, "1p+0"},
+    {0x1p+9f, chars_format::hex, 0, "1p+9"},
+    {0x1p+99f, chars_format::hex, 0, "1p+99"},
+    {0x1p+109f, chars_format::hex, 0, "1p+109"},
+
+    // Test hexfloat hexits.
+    {0x1.0123p+0f, chars_format::hex, 4, "1.0123p+0"},
+    {0x1.4567p+0f, chars_format::hex, 4, "1.4567p+0"},
+    {0x1.89abp+0f, chars_format::hex, 4, "1.89abp+0"},
+    {0x1.cdefp+0f, chars_format::hex, 4, "1.cdefp+0"},
+
+    // Test varying precision. Negative precision requests full precision, not shortest round-trip.
+    {0x1.123456p+0f, chars_format::hex, -2, "1.123456p+0"},
+    {0x1.123456p+0f, chars_format::hex, -1, "1.123456p+0"},
+    {0x1.123456p+0f, chars_format::hex, 0, "1p+0"},
+    {0x1.123456p+0f, chars_format::hex, 1, "1.1p+0"},
+    {0x1.123456p+0f, chars_format::hex, 2, "1.12p+0"},
+    {0x1.123456p+0f, chars_format::hex, 3, "1.123p+0"},
+    {0x1.123456p+0f, chars_format::hex, 4, "1.1234p+0"},
+    {0x1.123456p+0f, chars_format::hex, 5, "1.12345p+0"},
+    {0x1.123456p+0f, chars_format::hex, 6, "1.123456p+0"},
+    {0x1.123456p+0f, chars_format::hex, 7, "1.1234560p+0"},
+    {0x1.123456p+0f, chars_format::hex, 8, "1.12345600p+0"},
+    {0x1.123456p+0f, chars_format::hex, 9, "1.123456000p+0"},
+
+    // Test rounding at every position.
+    {0x1.ccccccp+0f, chars_format::hex, 0, "2p+0"},
+    {0x1.ccccccp+0f, chars_format::hex, 1, "1.dp+0"},
+    {0x1.ccccccp+0f, chars_format::hex, 2, "1.cdp+0"},
+    {0x1.ccccccp+0f, chars_format::hex, 3, "1.ccdp+0"},
+    {0x1.ccccccp+0f, chars_format::hex, 4, "1.cccdp+0"},
+    {0x1.ccccccp+0f, chars_format::hex, 5, "1.ccccdp+0"},
+    {0x1.ccccccp+0f, chars_format::hex, 6, "1.ccccccp+0"},
+
+    // Test all combinations of least significant bit, round bit, and trailing bits.
+    {0x1.04000p+0f, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 0, Trailing 0
+    {0x1.04001p+0f, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 0 and Trailing 1 in different hexits
+    {0x1.04200p+0f, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 0 and Trailing 1 in same hexit
+    {0x1.04800p+0f, chars_format::hex, 2, "1.04p+0"}, // Lsb 0, Round 1, Trailing 0
+    {0x1.04801p+0f, chars_format::hex, 2, "1.05p+0"}, // Lsb 0, Round 1 and Trailing 1 in different hexits
+    {0x1.04900p+0f, chars_format::hex, 2, "1.05p+0"}, // Lsb 0, Round 1 and Trailing 1 in same hexit
+    {0x1.05000p+0f, chars_format::hex, 2, "1.05p+0"}, // Lsb 1, Round 0, Trailing 0
+    {0x1.05001p+0f, chars_format::hex, 2, "1.05p+0"}, // Lsb 1, Round 0 and Trailing 1 in different hexits
+    {0x1.05200p+0f, chars_format::hex, 2, "1.05p+0"}, // Lsb 1, Round 0 and Trailing 1 in same hexit
+    {0x1.05800p+0f, chars_format::hex, 2, "1.06p+0"}, // Lsb 1, Round 1, Trailing 0
+    {0x1.05801p+0f, chars_format::hex, 2, "1.06p+0"}, // Lsb 1, Round 1 and Trailing 1 in different hexits
+    {0x1.05900p+0f, chars_format::hex, 2, "1.06p+0"}, // Lsb 1, Round 1 and Trailing 1 in same hexit
+
+    // Test carry propagation.
+    {0x1.0afffep+0f, chars_format::hex, 5, "1.0b000p+0"},
+
+    // Test carry propagation into the leading hexit.
+    {0x0.fffffep-126f, chars_format::hex, 5, "1.00000p-126"},
+    {0x1.fffffep+127f, chars_format::hex, 5, "2.00000p+127"},
+
+    // Test how the leading hexit participates in the rounding decision.
+    {0x0.000p+0f, chars_format::hex, 0, "0p+0"},
+    {0x0.001p-126f, chars_format::hex, 0, "0p-126"},
+    {0x0.200p-126f, chars_format::hex, 0, "0p-126"},
+    {0x0.800p-126f, chars_format::hex, 0, "0p-126"},
+    {0x0.801p-126f, chars_format::hex, 0, "1p-126"},
+    {0x0.900p-126f, chars_format::hex, 0, "1p-126"},
+    {0x1.000p+0f, chars_format::hex, 0, "1p+0"},
+    {0x1.001p+0f, chars_format::hex, 0, "1p+0"},
+    {0x1.200p+0f, chars_format::hex, 0, "1p+0"},
+    {0x1.800p+0f, chars_format::hex, 0, "2p+0"},
+    {0x1.801p+0f, chars_format::hex, 0, "2p+0"},
+    {0x1.900p+0f, chars_format::hex, 0, "2p+0"},
+};
+
+#endif // FLOAT_HEX_PRECISION_TO_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/float_scientific_precision_to_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+
+// This file contains test cases derived from:
+// https://github.com/ulfjack/ryu
+// See xcharconv_ryu.h for the exact commit.
+// (Keep the cgmanifest.json commitHash in sync.)
+
+
+#ifndef FLOAT_SCIENTIFIC_PRECISION_TO_CHARS_TEST_CASES_HPP
+#define FLOAT_SCIENTIFIC_PRECISION_TO_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr FloatPrecisionToCharsTestCase float_scientific_precision_to_chars_test_cases[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0f, chars_format::scientific, 4, "0.0000e+00"},
+    {-0.0f, chars_format::scientific, 4, "-0.0000e+00"},
+    {float_inf, chars_format::scientific, 4, "inf"},
+    {-float_inf, chars_format::scientific, 4, "-inf"},
+    {float_nan, chars_format::scientific, 4, "nan"},
+    {-float_nan, chars_format::scientific, 4, "-nan(ind)"},
+    {float_nan_payload, chars_format::scientific, 4, "nan"},
+    {-float_nan_payload, chars_format::scientific, 4, "-nan"},
+    {1.729f, chars_format::scientific, 4, "1.7290e+00"},
+    {-1.729f, chars_format::scientific, 4, "-1.7290e+00"},
+
+    // Ryu Printf Zero
+    {0.0f, chars_format::scientific, 4, "0.0000e+00"},
+    {0.0f, chars_format::scientific, 3, "0.000e+00"},
+    {0.0f, chars_format::scientific, 2, "0.00e+00"},
+    {0.0f, chars_format::scientific, 1, "0.0e+00"},
+    {0.0f, chars_format::scientific, 0, "0e+00"},
+
+    // Test corner cases.
+    {0x0.000002p-126f, chars_format::scientific, 104, // min subnormal
+        "1."
+        "40129846432481707092372958328991613128026194187651577175706828388979108268586060148663818836212158203125e-"
+        "45"},
+    {0x0.fffffep-126f, chars_format::scientific, 111, // max subnormal
+        "1."
+        "1754942106924410754870294448492873488270524287458933338571745305715888704756189042655023513361811637878417"
+        "96875e-38"},
+    {0x1p-126f, chars_format::scientific, 88, // min normal
+        "1.1754943508222875079687365372222456778186655567720875215087517062784172594547271728515625e-38"},
+    {0x1.fffffep+127f, chars_format::scientific, 37, // max normal
+        "3.4028234663852885981170418348451692544e+38"},
+
+    // Ryu Printf AllPowersOfTen
+    // These values test every power of ten that's within the range of floats.
+    {1e-44f, chars_format::scientific, 104,
+        "9."
+        "80908925027371949646610708302941291896183359313561040229947798722853757880102421040646731853485107421875e-"
+        "45"},
+    {1e-43f, chars_format::scientific, 105,
+        "9."
+        "949219096706201203558480041358404532089859787323261979475184815617516687069610270555131137371063232421875e"
+        "-44"},
+    {1e-42f, chars_format::scientific, 106,
+        "1."
+        "0005271035279193886395429224690001177341070264998322610345467546973108330377044694614596664905548095703125"
+        "e-42"},
+    {1e-41f, chars_format::scientific, 102,
+        "9.999665841421894618111734306356841512815949217230816547258439273837549166046301252208650112152099609375e-"
+        "42"},
+    {1e-40f, chars_format::scientific, 107,
+        "9."
+        "9999461011147595815259190522734994960422052696191918504127906874943271242628384243289474397897720336914062"
+        "5e-41"},
+    {1e-39f, chars_format::scientific, 107,
+        "1."
+        "0000002153053332574208756001456831092687456480096866911043660970225682715906145858753006905317306518554687"
+        "5e-39"},
+    {1e-38f, chars_format::scientific, 109,
+        "9."
+        "9999993504564039245746141539976645128551939195729831580121174560891149363239804870318039320409297943115234"
+        "375e-39"},
+    {1e-37f, chars_format::scientific, 107,
+        "9."
+        "9999999109757896545014425234894978288216464316777599086184261589164284922404135613760445266962051391601562"
+        "5e-38"},
+    {1e-36f, chars_format::scientific, 107,
+        "1."
+        "0000000359391298238442905219082964481594808441361581309103473121178279336973560020851437002420425415039062"
+        "5e-36"},
+    {1e-35f, chars_format::scientific, 104,
+        "1."
+        "00000001800250948048663201408455778204855436374880527489094543362735389990803014370612800121307373046875e-"
+        "35"},
+    {1e-34f, chars_format::scientific, 102,
+        "1.000000046701102029858885626602539647826036732368569844521988439212112353970951517112553119659423828125e-"
+        "34"},
+    {1e-33f, chars_format::scientific, 98,
+        "1.00000002374222799036108273658815415520405083747275818881715403474430559072061441838741302490234375e-33"},
+    {1e-32f, chars_format::scientific, 98,
+        "1.00000002374222799036108273658815415520405083747275818881715403474430559072061441838741302490234375e-32"},
+    {1e-31f, chars_format::scientific, 94,
+        "9.9999997966118983452530118776053400936983791927279980986387197816611660527996718883514404296875e-32"},
+    {1e-30f, chars_format::scientific, 88,
+        "1.0000000031710768509710513471352647538147514756461109453056224083411507308483123779296875e-30"},
+    {1e-29f, chars_format::scientific, 88,
+        "1.0000000031710768509710513471352647538147514756461109453056224083411507308483123779296875e-29"},
+    {1e-28f, chars_format::scientific, 88,
+        "1.0000000031710768509710513471352647538147514756461109453056224083411507308483123779296875e-28"},
+    {1e-27f, chars_format::scientific, 85,
+        "1.0000000272452011558114995103349890361263429573723815479979748488403856754302978515625e-27"},
+    {1e-26f, chars_format::scientific, 82,
+        "9.9999998872660226806678244921543018442779658661034858369021094404160976409912109375e-27"},
+    {1e-25f, chars_format::scientific, 79,
+        "1.0000000195414813782625560981110772657866336832199749551364220678806304931640625e-25"},
+    {1e-24f, chars_format::scientific, 79,
+        "1.0000000195414813782625560981110772657866336832199749551364220678806304931640625e-24"},
+    {1e-23f, chars_format::scientific, 75,
+        "9.999999998199587477372609628178631337169779413898140774108469486236572265625e-24"},
+    {1e-22f, chars_format::scientific, 75,
+        "1.000000031374394956577733179287005745028427128318071481771767139434814453125e-22"},
+    {1e-21f, chars_format::scientific, 66, "9.999999682655225388967887463487205224055287544615566730499267578125e-22"},
+    {1e-20f, chars_format::scientific, 66, "9.999999682655225388967887463487205224055287544615566730499267578125e-21"},
+    {1e-19f, chars_format::scientific, 66, "9.999999682655225388967887463487205224055287544615566730499267578125e-20"},
+    {1e-18f, chars_format::scientific, 65, "1.00000004581370496574313326554328540396454627625644207000732421875e-18"},
+    {1e-17f, chars_format::scientific, 61, "9.9999998377515902426605765018763349871733225882053375244140625e-18"},
+    {1e-16f, chars_format::scientific, 61, "1.0000000168623835263871646450439811815158464014530181884765625e-16"},
+    {1e-15f, chars_format::scientific, 58, "1.0000000036274937255387218471014421083964407444000244140625e-15"},
+    {1e-14f, chars_format::scientific, 53, "9.99999982451670044181213370393379591405391693115234375e-15"},
+    {1e-13f, chars_format::scientific, 53, "9.99999982451670044181213370393379591405391693115234375e-14"},
+    {1e-12f, chars_format::scientific, 48, "9.999999960041972002500187954865396022796630859375e-13"},
+    {1e-11f, chars_format::scientific, 48, "9.999999960041972002500187954865396022796630859375e-12"},
+    {1e-10f, chars_format::scientific, 47, "1.00000001335143196001808973960578441619873046875e-10"},
+    {1e-09f, chars_format::scientific, 43, "9.9999997171806853657471947371959686279296875e-10"},
+    {1e-08f, chars_format::scientific, 41, "9.99999993922529029077850282192230224609375e-09"},
+    {1e-07f, chars_format::scientific, 40, "1.0000000116860974230803549289703369140625e-07"},
+    {1e-06f, chars_format::scientific, 36, "9.999999974752427078783512115478515625e-07"},
+    {1e-05f, chars_format::scientific, 32, "9.99999974737875163555145263671875e-06"},
+    {1e-04f, chars_format::scientific, 32, "9.99999974737875163555145263671875e-05"},
+    {1e-03f, chars_format::scientific, 30, "1.000000047497451305389404296875e-03"},
+    {1e-02f, chars_format::scientific, 26, "9.99999977648258209228515625e-03"},
+    {1e-01f, chars_format::scientific, 26, "1.00000001490116119384765625e-01"},
+    {1e+00f, chars_format::scientific, 0, "1e+00"},
+    {1e+01f, chars_format::scientific, 0, "1e+01"},
+    {1e+02f, chars_format::scientific, 0, "1e+02"},
+    {1e+03f, chars_format::scientific, 0, "1e+03"},
+    {1e+04f, chars_format::scientific, 0, "1e+04"},
+    {1e+05f, chars_format::scientific, 0, "1e+05"},
+    {1e+06f, chars_format::scientific, 0, "1e+06"},
+    {1e+07f, chars_format::scientific, 0, "1e+07"},
+    {1e+08f, chars_format::scientific, 0, "1e+08"},
+    {1e+09f, chars_format::scientific, 0, "1e+09"},
+    {1e+10f, chars_format::scientific, 0, "1e+10"},
+    {1e+11f, chars_format::scientific, 10, "9.9999997952e+10"},
+    {1e+12f, chars_format::scientific, 11, "9.99999995904e+11"},
+    {1e+13f, chars_format::scientific, 12, "9.999999827968e+12"},
+    {1e+14f, chars_format::scientific, 14, "1.00000000376832e+14"},
+    {1e+15f, chars_format::scientific, 14, "9.99999986991104e+14"},
+    {1e+16f, chars_format::scientific, 16, "1.0000000272564224e+16"},
+    {1e+17f, chars_format::scientific, 16, "9.9999998430674944e+16"},
+    {1e+18f, chars_format::scientific, 16, "9.9999998430674944e+17"},
+    {1e+19f, chars_format::scientific, 18, "9.999999980506447872e+18"},
+    {1e+20f, chars_format::scientific, 20, "1.00000002004087734272e+20"},
+    {1e+21f, chars_format::scientific, 20, "1.00000002004087734272e+21"},
+    {1e+22f, chars_format::scientific, 21, "9.999999778196308361216e+21"},
+    {1e+23f, chars_format::scientific, 21, "9.999999778196308361216e+22"},
+    {1e+24f, chars_format::scientific, 24, "1.000000013848427855085568e+24"},
+    {1e+25f, chars_format::scientific, 24, "9.999999562023526247432192e+24"},
+    {1e+26f, chars_format::scientific, 26, "1.00000002537764290115403776e+26"},
+    {1e+27f, chars_format::scientific, 26, "9.99999988484154753734934528e+26"},
+    {1e+28f, chars_format::scientific, 27, "9.999999442119689768320106496e+27"},
+    {1e+29f, chars_format::scientific, 29, "1.00000001504746621987668885504e+29"},
+    {1e+30f, chars_format::scientific, 29, "1.00000001504746621987668885504e+30"},
+    {1e+31f, chars_format::scientific, 30, "9.999999848243207295109594873856e+30"},
+    {1e+32f, chars_format::scientific, 32, "1.00000003318135351409612647563264e+32"},
+    {1e+33f, chars_format::scientific, 32, "9.99999994495727286427992885035008e+32"},
+    {1e+34f, chars_format::scientific, 33, "9.999999790214767953607394487959552e+33"},
+    {1e+35f, chars_format::scientific, 34, "1.0000000409184787596297531937521664e+35"},
+    {1e+36f, chars_format::scientific, 35, "9.99999961690316245365415600208216064e+35"},
+    {1e+37f, chars_format::scientific, 36, "9.999999933815812510711506376257961984e+36"},
+    {1e+38f, chars_format::scientific, 37, "9.9999996802856924650656260769173209088e+37"},
+
+    // Ryu Printf RoundToEven
+    {0.125f, chars_format::scientific, 2, "1.25e-01"},
+    {0.125f, chars_format::scientific, 1, "1.2e-01"},
+    {0.375f, chars_format::scientific, 2, "3.75e-01"},
+    {0.375f, chars_format::scientific, 1, "3.8e-01"},
+
+    // Ryu Printf RoundToEvenInteger
+    {2.5f, chars_format::scientific, 1, "2.5e+00"},
+    {2.5f, chars_format::scientific, 0, "2e+00"},
+    {3.5f, chars_format::scientific, 1, "3.5e+00"},
+    {3.5f, chars_format::scientific, 0, "4e+00"},
+
+    // Ryu Printf NonRoundToEvenScenarios
+    {0.748046875f, chars_format::scientific, 2, "7.48e-01"},
+    {0.748046875f, chars_format::scientific, 1, "7.5e-01"},
+    {0.748046875f, chars_format::scientific, 0, "7e-01"}, // 0.75 would round to "8e-01", but this is smaller
+
+    {0.2509765625f, chars_format::scientific, 2, "2.51e-01"},
+    {0.2509765625f, chars_format::scientific, 1, "2.5e-01"},
+    {0.2509765625f, chars_format::scientific, 0, "3e-01"}, // 0.25 would round to "2e-01", but this is larger
+
+    {0x1.000002p-2f, chars_format::scientific, 24, "2.500000298023223876953125e-01"},
+    {0x1.000002p-2f, chars_format::scientific, 2, "2.50e-01"},
+    {0x1.000002p-2f, chars_format::scientific, 1, "2.5e-01"},
+    {0x1.000002p-2f, chars_format::scientific, 0, "3e-01"}, // 0.25 would round to "2e-01", but this is larger (again)
+
+    // More rounding tests.
+    {9.5f, chars_format::scientific, 1, "9.5e+00"},
+    {9.5f, chars_format::scientific, 0, "1e+01"},
+    {10.5f, chars_format::scientific, 2, "1.05e+01"},
+    {10.5f, chars_format::scientific, 1, "1.0e+01"},
+
+    {1.241f, chars_format::scientific, 3, "1.241e+00"},
+    {1.241f, chars_format::scientific, 1, "1.2e+00"},
+    {1.251f, chars_format::scientific, 3, "1.251e+00"},
+    {1.251f, chars_format::scientific, 1, "1.3e+00"},
+    {1.261f, chars_format::scientific, 3, "1.261e+00"},
+    {1.261f, chars_format::scientific, 1, "1.3e+00"},
+    {1.341f, chars_format::scientific, 3, "1.341e+00"},
+    {1.341f, chars_format::scientific, 1, "1.3e+00"},
+    {1.351f, chars_format::scientific, 3, "1.351e+00"},
+    {1.351f, chars_format::scientific, 1, "1.4e+00"},
+    {1.361f, chars_format::scientific, 3, "1.361e+00"},
+    {1.361f, chars_format::scientific, 1, "1.4e+00"},
+
+    {2.41f, chars_format::scientific, 2, "2.41e+00"},
+    {2.41f, chars_format::scientific, 0, "2e+00"},
+    {2.51f, chars_format::scientific, 2, "2.51e+00"},
+    {2.51f, chars_format::scientific, 0, "3e+00"},
+    {2.61f, chars_format::scientific, 2, "2.61e+00"},
+    {2.61f, chars_format::scientific, 0, "3e+00"},
+    {3.41f, chars_format::scientific, 2, "3.41e+00"},
+    {3.41f, chars_format::scientific, 0, "3e+00"},
+    {3.51f, chars_format::scientific, 2, "3.51e+00"},
+    {3.51f, chars_format::scientific, 0, "4e+00"},
+    {3.61f, chars_format::scientific, 2, "3.61e+00"},
+    {3.61f, chars_format::scientific, 0, "4e+00"},
+
+    // Ryu Printf VaryingPrecision
+    {1.142857f, chars_format::scientific, 28, "1.1428569555282592773437500000e+00"},
+    {1.142857f, chars_format::scientific, 27, "1.142856955528259277343750000e+00"},
+    {1.142857f, chars_format::scientific, 26, "1.14285695552825927734375000e+00"},
+    {1.142857f, chars_format::scientific, 25, "1.1428569555282592773437500e+00"},
+    {1.142857f, chars_format::scientific, 24, "1.142856955528259277343750e+00"},
+    {1.142857f, chars_format::scientific, 23, "1.14285695552825927734375e+00"},
+    {1.142857f, chars_format::scientific, 22, "1.1428569555282592773438e+00"},
+    {1.142857f, chars_format::scientific, 21, "1.142856955528259277344e+00"},
+    {1.142857f, chars_format::scientific, 20, "1.14285695552825927734e+00"},
+    {1.142857f, chars_format::scientific, 19, "1.1428569555282592773e+00"},
+    {1.142857f, chars_format::scientific, 18, "1.142856955528259277e+00"},
+    {1.142857f, chars_format::scientific, 17, "1.14285695552825928e+00"},
+    {1.142857f, chars_format::scientific, 16, "1.1428569555282593e+00"},
+    {1.142857f, chars_format::scientific, 15, "1.142856955528259e+00"},
+    {1.142857f, chars_format::scientific, 14, "1.14285695552826e+00"},
+    {1.142857f, chars_format::scientific, 13, "1.1428569555283e+00"},
+    {1.142857f, chars_format::scientific, 12, "1.142856955528e+00"},
+    {1.142857f, chars_format::scientific, 11, "1.14285695553e+00"},
+    {1.142857f, chars_format::scientific, 10, "1.1428569555e+00"},
+    {1.142857f, chars_format::scientific, 9, "1.142856956e+00"},
+    {1.142857f, chars_format::scientific, 8, "1.14285696e+00"},
+    {1.142857f, chars_format::scientific, 7, "1.1428570e+00"},
+    {1.142857f, chars_format::scientific, 6, "1.142857e+00"},
+    {1.142857f, chars_format::scientific, 5, "1.14286e+00"},
+    {1.142857f, chars_format::scientific, 4, "1.1429e+00"},
+    {1.142857f, chars_format::scientific, 3, "1.143e+00"},
+    {1.142857f, chars_format::scientific, 2, "1.14e+00"},
+    {1.142857f, chars_format::scientific, 1, "1.1e+00"},
+    {1.142857f, chars_format::scientific, 0, "1e+00"},
+
+    // Negative precision requests 6 digits of precision.
+    {1.142857f, chars_format::scientific, -1, "1.142857e+00"},
+    {1.142857f, chars_format::scientific, -2, "1.142857e+00"},
+    {1.142857f, chars_format::scientific, -3, "1.142857e+00"},
+
+    // Ryu Printf Carrying
+    {2.0009f, chars_format::scientific, 4, "2.0009e+00"},
+    {2.0009f, chars_format::scientific, 3, "2.001e+00"},
+    {2.0029f, chars_format::scientific, 4, "2.0029e+00"},
+    {2.0029f, chars_format::scientific, 3, "2.003e+00"},
+    {2.0099f, chars_format::scientific, 4, "2.0099e+00"},
+    {2.0099f, chars_format::scientific, 3, "2.010e+00"},
+    {2.0299f, chars_format::scientific, 4, "2.0299e+00"},
+    {2.0299f, chars_format::scientific, 3, "2.030e+00"},
+    {2.0999f, chars_format::scientific, 4, "2.0999e+00"},
+    {2.0999f, chars_format::scientific, 3, "2.100e+00"},
+    {2.2999f, chars_format::scientific, 4, "2.2999e+00"},
+    {2.2999f, chars_format::scientific, 3, "2.300e+00"},
+    {2.9999f, chars_format::scientific, 4, "2.9999e+00"},
+    {2.9999f, chars_format::scientific, 3, "3.000e+00"},
+    {9.9999f, chars_format::scientific, 4, "9.9999e+00"},
+    {9.9999f, chars_format::scientific, 3, "1.000e+01"},
+
+    {2.09f, chars_format::scientific, 2, "2.09e+00"},
+    {2.09f, chars_format::scientific, 1, "2.1e+00"},
+    {2.29f, chars_format::scientific, 2, "2.29e+00"},
+    {2.29f, chars_format::scientific, 1, "2.3e+00"},
+    {2.99f, chars_format::scientific, 2, "2.99e+00"},
+    {2.99f, chars_format::scientific, 1, "3.0e+00"},
+    {9.99f, chars_format::scientific, 2, "9.99e+00"},
+    {9.99f, chars_format::scientific, 1, "1.0e+01"},
+
+    {2.9f, chars_format::scientific, 1, "2.9e+00"},
+    {2.9f, chars_format::scientific, 0, "3e+00"},
+    {9.9f, chars_format::scientific, 1, "9.9e+00"},
+    {9.9f, chars_format::scientific, 0, "1e+01"},
+
+    // Ryu Printf Exponents
+    {9.99e-10f, chars_format::scientific, 2, "9.99e-10"},
+    {9.99e-09f, chars_format::scientific, 2, "9.99e-09"},
+    {9.99e-01f, chars_format::scientific, 2, "9.99e-01"},
+    {9.99e+00f, chars_format::scientific, 2, "9.99e+00"},
+    {9.99e+01f, chars_format::scientific, 2, "9.99e+01"},
+    {9.99e+09f, chars_format::scientific, 2, "9.99e+09"},
+    {9.99e+10f, chars_format::scientific, 2, "9.99e+10"},
+
+    {9.99e-10f, chars_format::scientific, 1, "1.0e-09"},
+    {9.99e-09f, chars_format::scientific, 1, "1.0e-08"},
+    {9.99e-01f, chars_format::scientific, 1, "1.0e+00"},
+    {9.99e+00f, chars_format::scientific, 1, "1.0e+01"},
+    {9.99e+01f, chars_format::scientific, 1, "1.0e+02"},
+    {9.99e+09f, chars_format::scientific, 1, "1.0e+10"},
+    {9.99e+10f, chars_format::scientific, 1, "1.0e+11"},
+
+    // Ryu Printf AllBinaryExponents
+    // These values test every binary exponent.
+    // The mantissas were randomly generated.
+    {0x0.bafab0p-126f, chars_format::scientific, 107,
+        "8."
+        "5856660078164374052571520381239855817217629811131320365461649230225810169869760102301370352506637573242187"
+        "5e-39"},
+    {0x1.2c4906p-126f, chars_format::scientific, 111,
+        "1."
+        "3788422360444725799170555395988202383016563601793620435599297375199720136484948795896343654021620750427246"
+        "09375e-38"},
+    {0x1.da6c8cp-125f, chars_format::scientific, 109,
+        "4."
+        "3568964460614492296234103491671745446178474818057230651136547036595368653788540314053534530103206634521484"
+        "375e-38"},
+    {0x1.094fd8p-124f, chars_format::scientific, 107,
+        "4."
+        "8730098044956940648689859309723501868625857818278160902221179289536129308757494982273783534765243530273437"
+        "5e-38"},
+    {0x1.1fba2ap-123f, chars_format::scientific, 109,
+        "1."
+        "0569428191822507939881039060004188252129978601750040353991776209794002661102041429330711252987384796142578"
+        "125e-37"},
+    {0x1.05c066p-122f, chars_format::scientific, 108,
+        "1."
+        "9230467241438048605749036664954171842721044312192826420869210321670447760844524509593611583113670349121093"
+        "75e-37"},
+    {0x1.aa97aep-121f, chars_format::scientific, 107,
+        "6."
+        "2682134052278382034317570078635218253248121012038564692208751497667224006349329101794864982366561889648437"
+        "5e-37"},
+    {0x1.dd39a8p-120f, chars_format::scientific, 105,
+        "1."
+        "402438874646247750851657016594307463985884969771101485328502708228859408023936339304782450199127197265625e"
+        "-36"},
+    {0x1.d47ee4p-119f, chars_format::scientific, 105,
+        "2."
+        "753570046800320919541684228734204622774621916697559471583583415484064449429979504202492535114288330078125e"
+        "-36"},
+    {0x1.3d3c36p-118f, chars_format::scientific, 105,
+        "3."
+        "729081842766376549743290774072513136892856721536744273788293430570150999159295679419301450252532958984375e"
+        "-36"},
+    {0x1.1661f4p-117f, chars_format::scientific, 103,
+        "6."
+        "5447441644065192772010189083715139205202243608571574700187600294454259852727773250080645084381103515625e-"
+        "36"},
+    {0x1.b68df4p-116f, chars_format::scientific, 103,
+        "2."
+        "0620733697737581832019236718658803118114911610758483179403903647053386549714559805579483509063720703125e-"
+        "35"},
+    {0x1.d99cbcp-115f, chars_format::scientific, 102,
+        "4.453828135148790991673442414370889923378622963993538561236896870798585013062620419077575206756591796875e-"
+        "35"},
+    {0x1.fd046ep-114f, chars_format::scientific, 102,
+        "9.573551435136219346253356313052326716805272442482100391194957227092299234527672524563968181610107421875e-"
+        "35"},
+    {0x1.89834cp-113f, chars_format::scientific, 101,
+        "1.48023092977964777039833097802364118989950189925000614428441357561805347131667076610028743743896484375e-"
+        "34"},
+    {0x1.44f9f6p-112f, chars_format::scientific, 101,
+        "2.44485077761403269855863218622241304191185681346184344636825701291282797456005937419831752777099609375e-"
+        "34"},
+    {0x1.610156p-111f, chars_format::scientific, 100,
+        "5.3114321941046389584918230189833796378476189953948627677188069895475308612731168977916240692138671875e-"
+        "34"},
+    {0x1.1c4ce0p-110f, chars_format::scientific, 95,
+        "8.55535074104030543315341178235051098966105705542347053919882693406862017582170665264129638671875e-34"},
+    {0x1.c8846ap-109f, chars_format::scientific, 99,
+        "2.747563210400574676694231398741237029228255561600948508123483382536988983702030964195728302001953125e-"
+        "33"},
+    {0x1.49aaa6p-108f, chars_format::scientific, 98,
+        "3.96821729911656973098277999199730227135040686156682094762847279323381144422455690801143646240234375e-33"},
+    {0x1.f5603cp-107f, chars_format::scientific, 97,
+        "1.2070186113858457615715036175854047096256968023404067681496332209434285687166266143321990966796875e-32"},
+    {0x1.b7bbf8p-106f, chars_format::scientific, 95,
+        "2.11724341322508937840915176712265363597160619557838059749677039889093066449277102947235107421875e-32"},
+    {0x1.6d305cp-105f, chars_format::scientific, 95,
+        "3.51664122601460292174574136500884378151845989294218826175242309517443572985939681529998779296875e-32"},
+    {0x1.dd9944p-104f, chars_format::scientific, 94,
+        "9.1982162588143308372426801228237163172804681524337790977929874003393706516362726688385009765625e-32"},
+    {0x1.0f4254p-103f, chars_format::scientific, 94,
+        "1.0448520245617299544506055022011322932281191403904399041258077573957052663899958133697509765625e-31"},
+    {0x1.049450p-102f, chars_format::scientific, 91,
+        "2.0074302591139273483884727591728498336691676235299559849512007758676190860569477081298828125e-31"},
+    {0x1.28d030p-101f, chars_format::scientific, 90,
+        "4.573131937693259427041496124538667251427229422876784281637441154089174233376979827880859375e-31"},
+    {0x1.28a2bep-100f, chars_format::scientific, 92,
+        "9.14079359487553225693590893672771706036816190371857397678478918123801122419536113739013671875e-31"},
+    {0x1.e674d2p-99f, chars_format::scientific, 92,
+        "2.99801859623548450508972193909865244412972328427583780519061207314734929241240024566650390625e-30"},
+    {0x1.227314p-98f, chars_format::scientific, 90,
+        "3.580066786954745677669456497979475880433682721056161402106710056614247150719165802001953125e-30"},
+    {0x1.735b6cp-97f, chars_format::scientific, 89,
+        "9.15465972623783196037990815292079067038371088262625752118850641636527143418788909912109375e-30"},
+    {0x1.ef60b4p-96f, chars_format::scientific, 89,
+        "2.44240085996903849216356078751341022854748745722804070812372856380534358322620391845703125e-29"},
+    {0x1.f58d34p-95f, chars_format::scientific, 88,
+        "4.9456803654801575096422210377919300096339643075561698370989915929385460913181304931640625e-29"},
+    {0x1.a9fa8ap-94f, chars_format::scientific, 88,
+        "8.4009479452815486408032573050798399509585053673323129519445728874416090548038482666015625e-29"},
+    {0x1.2ebd9ap-93f, chars_format::scientific, 88,
+        "1.1941012414974986903540736041200443068748917913209084407100135649670846760272979736328125e-28"},
+    {0x1.1c25bep-92f, chars_format::scientific, 87,
+        "2.241527991772840369420073304083191365256388471842441401093992681126110255718231201171875e-28"},
+    {0x1.80d526p-91f, chars_format::scientific, 86,
+        "6.07158803876554990450680694292368438689814417845436178566842500003986060619354248046875e-28"},
+    {0x1.16cdd0p-90f, chars_format::scientific, 82,
+        "8.7975016152851199468348749874043115366058394333226289063532021827995777130126953125e-28"},
+    {0x1.be00c0p-89f, chars_format::scientific, 80,
+        "2.81467419875603623917323685831723008277625852624481694874702952802181243896484375e-27"},
+    {0x1.dbe376p-88f, chars_format::scientific, 84,
+        "6.006557569745856595501482055708847377292216272726133041715002036653459072113037109375e-27"},
+    {0x1.75b358p-87f, chars_format::scientific, 81,
+        "9.433528423839338263891493367075328273989136274035871565502020530402660369873046875e-27"},
+    {0x1.5e56fap-86f, chars_format::scientific, 83,
+        "1.76876373794073549186243776242822499413496518949617808402763330377638339996337890625e-26"},
+    {0x1.1542e6p-85f, chars_format::scientific, 82,
+        "2.7996239036498255213653797353262236131499034186287389047720353119075298309326171875e-26"},
+    {0x1.37b7a6p-84f, chars_format::scientific, 81,
+        "6.295082290272475030989309944874260889838800403506269276476814411580562591552734375e-26"},
+    {0x1.31f62ap-83f, chars_format::scientific, 81,
+        "1.235768973696664669858567539321145118649987459935601918914471752941608428955078125e-25"},
+    {0x1.ac3560p-82f, chars_format::scientific, 76,
+        "3.4590406845628797200186450581230516131137076030199750675819814205169677734375e-25"},
+    {0x1.a7db5cp-81f, chars_format::scientific, 78,
+        "6.847777099176331341674240101847394713956151957034990118700079619884490966796875e-25"},
+    {0x1.40189cp-80f, chars_format::scientific, 78,
+        "1.034286379672715366987641733210033664035198963659922810620628297328948974609375e-24"},
+    {0x1.aad1eep-79f, chars_format::scientific, 78,
+        "2.758259846499093682487211692864773559218105614121441249153576791286468505859375e-24"},
+    {0x1.49824cp-78f, chars_format::scientific, 76,
+        "4.2588036474940459085811637121780459484809977510622047702781856060028076171875e-24"},
+    {0x1.955292p-77f, chars_format::scientific, 77,
+        "1.04773420985315373838626628182169411331037256474019159213639795780181884765625e-23"},
+    {0x1.d8ca0cp-76f, chars_format::scientific, 75,
+        "2.444263111177596802332967266437459101513507420122550684027373790740966796875e-23"},
+    {0x1.28b5aap-75f, chars_format::scientific, 75,
+        "3.067905619497844072028707730390270809472941238027487997896969318389892578125e-23"},
+    {0x1.e5fda8p-74f, chars_format::scientific, 73,
+        "1.0050055115902033206854316793794380802129495577901252545416355133056640625e-22"},
+    {0x1.fd929cp-73f, chars_format::scientific, 73,
+        "2.1075432611470358337541921610390309449467594049565377645194530487060546875e-22"},
+    {0x1.c0b84cp-72f, chars_format::scientific, 72,
+        "3.711724097438896357340602997067040280665395357573288492858409881591796875e-22"},
+    {0x1.5cfeaep-71f, chars_format::scientific, 72,
+        "5.773635352424624465965559338086719731730767080080113373696804046630859375e-22"},
+    {0x1.bcce4ap-70f, chars_format::scientific, 72,
+        "1.471738991536079335112024613790339400143380998997599817812442779541015625e-21"},
+    {0x1.edf106p-69f, chars_format::scientific, 71,
+        "3.26863064574260634910627773444362353938430487687583081424236297607421875e-21"},
+    {0x1.30b422p-68f, chars_format::scientific, 70,
+        "4.0327191475944672156035895296995186232180685692583210766315460205078125e-21"},
+    {0x1.7aa8d8p-67f, chars_format::scientific, 68,
+        "1.00230347240102665385544432156972316505516573670320212841033935546875e-20"},
+    {0x1.4ad4e0p-66f, chars_format::scientific, 65,
+        "1.75140760553442509348562143578487138029231573455035686492919921875e-20"},
+    {0x1.dde636p-65f, chars_format::scientific, 68,
+        "5.05995524921864861016965251964971894693690046551637351512908935546875e-20"},
+    {0x1.5df870p-64f, chars_format::scientific, 64,
+        "7.4109127331368847396687003781234892585416673682630062103271484375e-20"},
+    {0x1.c346fap-63f, chars_format::scientific, 67,
+        "1.9112335047873604296656620434025075638828639057464897632598876953125e-19"},
+    {0x1.58d2eap-62f, chars_format::scientific, 66,
+        "2.920771899491385068938311721231659845443573431111872196197509765625e-19"},
+    {0x1.0d4824p-61f, chars_format::scientific, 64,
+        "4.5618111223383324851561766710705825289551285095512866973876953125e-19"},
+    {0x1.04585cp-60f, chars_format::scientific, 63,
+        "8.820836917354691955064048547452415505176759324967861175537109375e-19"},
+    {0x1.55cf7ap-59f, chars_format::scientific, 64,
+        "2.3161977389916240139687737820128887733517331071197986602783203125e-18"},
+    {0x1.1fd8ecp-58f, chars_format::scientific, 62,
+        "3.90105904223582084021197668999292318403604440391063690185546875e-18"},
+    {0x1.0bc866p-57f, chars_format::scientific, 62,
+        "7.25826751123333980988787395016714754092390649020671844482421875e-18"},
+    {0x1.4dfa86p-56f, chars_format::scientific, 62,
+        "1.81050165732891247031242920595417444928898476064205169677734375e-17"},
+    {0x1.335daep-55f, chars_format::scientific, 61,
+        "3.3324681586205479543426333233213654239079914987087249755859375e-17"},
+    {0x1.5bc756p-54f, chars_format::scientific, 60,
+        "7.541247487712833172911197632259927559061907231807708740234375e-17"},
+    {0x1.9eb052p-53f, chars_format::scientific, 60,
+        "1.798425779915148827771409489884035792783834040164947509765625e-16"},
+    {0x1.13b6d2p-52f, chars_format::scientific, 59,
+        "2.39143897259270284301468922905087310937233269214630126953125e-16"},
+    {0x1.260438p-51f, chars_format::scientific, 56, "5.10037289299151118393549353413618518970906734466552734375e-16"},
+    {0x1.9e6b44p-50f, chars_format::scientific, 57, "1.437804758404521467129999479084290214814245700836181640625e-15"},
+    {0x1.89c0bcp-49f, chars_format::scientific, 56, "2.73220937993773164975674916377101908437907695770263671875e-15"},
+    {0x1.e30610p-48f, chars_format::scientific, 53, "6.70330015995791728133923470522859133780002593994140625e-15"},
+    {0x1.48b6e8p-47f, chars_format::scientific, 53, "9.12365953728740131101204724473063834011554718017578125e-15"},
+    {0x1.41382ep-46f, chars_format::scientific, 55, "1.7831261573081173821275768887062440626323223114013671875e-14"},
+    {0x1.383b8ep-45f, chars_format::scientific, 54, "3.466478609693256218715617933412431739270687103271484375e-14"},
+    {0x1.1e6564p-44f, chars_format::scientific, 52, "6.3592699357274684590635160930105485022068023681640625e-14"},
+    {0x1.c35e62p-43f, chars_format::scientific, 53, "2.00447961722950707130763703389675356447696685791015625e-13"},
+    {0x1.2a2f4ep-42f, chars_format::scientific, 52, "2.6484129017449731247069166784058324992656707763671875e-13"},
+    {0x1.69fae2p-41f, chars_format::scientific, 51, "6.430056682417417679431537180789746344089508056640625e-13"},
+    {0x1.4ccefep-40f, chars_format::scientific, 51, "1.182373535017766652543969030375592410564422607421875e-12"},
+    {0x1.aa9bf6p-39f, chars_format::scientific, 50, "3.03124083993189241681420753593556582927703857421875e-12"},
+    {0x1.3b9744p-38f, chars_format::scientific, 48, "4.484816164274096905728583806194365024566650390625e-12"},
+    {0x1.b2fc6ap-37f, chars_format::scientific, 49, "1.2363045483188006556929394719190895557403564453125e-11"},
+    {0x1.7bc418p-36f, chars_format::scientific, 46, "2.1587197307493255493682227097451686859130859375e-11"},
+    {0x1.f4a74cp-35f, chars_format::scientific, 46, "5.6917713597837149563929415307939052581787109375e-11"},
+    {0x1.89f248p-34f, chars_format::scientific, 44, "8.95730434269381703416001982986927032470703125e-11"},
+    {0x1.60ac54p-33f, chars_format::scientific, 45, "1.603771837555001411601551808416843414306640625e-10"},
+    {0x1.2f6d0ep-32f, chars_format::scientific, 45, "2.759643347172158200919511727988719940185546875e-10"},
+    {0x1.748684p-31f, chars_format::scientific, 43, "6.7761984912095840627443976700305938720703125e-10"},
+    {0x1.b4fa00p-30f, chars_format::scientific, 36, "1.589711473570787347853183746337890625e-09"},
+    {0x1.c204d8p-29f, chars_format::scientific, 41, "3.27431859403759517590515315532684326171875e-09"},
+    {0x1.50029ep-28f, chars_format::scientific, 42, "4.889592286616561978007666766643524169921875e-09"},
+    {0x1.56cf38p-27f, chars_format::scientific, 39, "9.977068060607052757404744625091552734375e-09"},
+    {0x1.0b5a5cp-26f, chars_format::scientific, 40, "1.5561990807100301026366651058197021484375e-08"},
+    {0x1.fc8250p-25f, chars_format::scientific, 37, "5.9198242752245278097689151763916015625e-08"},
+    {0x1.c66674p-24f, chars_format::scientific, 39, "1.057982927932243910618126392364501953125e-07"},
+    {0x1.4da57ep-23f, chars_format::scientific, 39, "1.553662372089092968963086605072021484375e-07"},
+    {0x1.4fcdacp-22f, chars_format::scientific, 37, "3.1274129241865011863410472869873046875e-07"},
+    {0x1.5eaff4p-21f, chars_format::scientific, 36, "6.532060297104180790483951568603515625e-07"},
+    {0x1.d2f696p-20f, chars_format::scientific, 37, "1.7395735767422593198716640472412109375e-06"},
+    {0x1.e4400cp-19f, chars_format::scientific, 35, "3.60794501830241642892360687255859375e-06"},
+    {0x1.03e624p-18f, chars_format::scientific, 34, "3.8727966966689564287662506103515625e-06"},
+    {0x1.bdb65ep-17f, chars_format::scientific, 35, "1.32832637973478995263576507568359375e-05"},
+    {0x1.57fb84p-16f, chars_format::scientific, 33, "2.050295370281673967838287353515625e-05"},
+    {0x1.fd2d62p-15f, chars_format::scientific, 33, "6.069866140023805201053619384765625e-05"},
+    {0x1.ca0c58p-14f, chars_format::scientific, 31, "1.0920720524154603481292724609375e-04"},
+    {0x1.988f70p-13f, chars_format::scientific, 29, "1.94816733710467815399169921875e-04"},
+    {0x1.032dd6p-12f, chars_format::scientific, 31, "2.4717240012250840663909912109375e-04"},
+    {0x1.571b08p-11f, chars_format::scientific, 28, "6.5442197956144809722900390625e-04"},
+    {0x1.53bedap-10f, chars_format::scientific, 30, "1.296026282943785190582275390625e-03"},
+    {0x1.ab2f36p-9f, chars_format::scientific, 29, "3.25915846042335033416748046875e-03"},
+    {0x1.7293dap-8f, chars_format::scientific, 28, "5.6545645929872989654541015625e-03"},
+    {0x1.825eb6p-7f, chars_format::scientific, 28, "1.1791075579822063446044921875e-02"},
+    {0x1.f45aa0p-6f, chars_format::scientific, 23, "3.05391848087310791015625e-02"},
+    {0x1.854d96p-5f, chars_format::scientific, 26, "4.75223474204540252685546875e-02"},
+    {0x1.5650cep-4f, chars_format::scientific, 25, "8.3573155105113983154296875e-02"},
+    {0x1.03acdap-3f, chars_format::scientific, 25, "1.2679453194141387939453125e-01"},
+    {0x1.6b9416p-2f, chars_format::scientific, 24, "3.550570905208587646484375e-01"},
+    {0x1.a8544ap-1f, chars_format::scientific, 23, "8.28768074512481689453125e-01"},
+    {0x1.0693f6p+0f, chars_format::scientific, 23, "1.02569520473480224609375e+00"},
+    {0x1.b9476ep+1f, chars_format::scientific, 22, "3.4474923610687255859375e+00"},
+    {0x1.3cb752p+2f, chars_format::scientific, 21, "4.948688983917236328125e+00"},
+    {0x1.bb8a64p+3f, chars_format::scientific, 20, "1.38606433868408203125e+01"},
+    {0x1.1de906p+4f, chars_format::scientific, 20, "1.78693904876708984375e+01"},
+    {0x1.d8e834p+5f, chars_format::scientific, 18, "5.911338043212890625e+01"},
+    {0x1.27cd38p+6f, chars_format::scientific, 16, "7.3950408935546875e+01"},
+    {0x1.3cdcd6p+7f, chars_format::scientific, 18, "1.584313201904296875e+02"},
+    {0x1.392656p+8f, chars_format::scientific, 17, "3.13149749755859375e+02"},
+    {0x1.c96aa8p+9f, chars_format::scientific, 14, "9.14833251953125e+02"},
+    {0x1.28b6b2p+10f, chars_format::scientific, 16, "1.1868546142578125e+03"},
+    {0x1.786090p+11f, chars_format::scientific, 12, "3.011017578125e+03"},
+    {0x1.79c6f6p+12f, chars_format::scientific, 14, "6.04443505859375e+03"},
+    {0x1.ef1840p+13f, chars_format::scientific, 9, "1.584303125e+04"},
+    {0x1.539fd0p+14f, chars_format::scientific, 10, "2.1735953125e+04"},
+    {0x1.b31804p+15f, chars_format::scientific, 11, "5.56920078125e+04"},
+    {0x1.ad4a9cp+16f, chars_format::scientific, 11, "1.09898609375e+05"},
+    {0x1.4c43a6p+17f, chars_format::scientific, 11, "1.70119296875e+05"},
+    {0x1.5598c6p+18f, chars_format::scientific, 10, "3.4979509375e+05"},
+    {0x1.73695ep+19f, chars_format::scientific, 9, "7.606509375e+05"},
+    {0x1.234f2ap+20f, chars_format::scientific, 9, "1.193202625e+06"},
+    {0x1.0a4cc8p+21f, chars_format::scientific, 6, "2.181529e+06"},
+    {0x1.90abd2p+22f, chars_format::scientific, 7, "6.5645965e+06"},
+    {0x1.62dde8p+23f, chars_format::scientific, 7, "1.1628276e+07"},
+    {0x1.9e3a8cp+24f, chars_format::scientific, 7, "2.7146892e+07"},
+    {0x1.53a3eap+25f, chars_format::scientific, 7, "4.4517332e+07"},
+    {0x1.41a1cep+26f, chars_format::scientific, 7, "8.4313912e+07"},
+    {0x1.8fdda4p+27f, chars_format::scientific, 8, "2.09644832e+08"},
+    {0x1.d0322ap+28f, chars_format::scientific, 8, "4.86744736e+08"},
+    {0x1.cdb764p+29f, chars_format::scientific, 8, "9.68289408e+08"},
+    {0x1.7620d8p+30f, chars_format::scientific, 9, "1.569207808e+09"},
+    {0x1.c18df6p+31f, chars_format::scientific, 9, "3.771136768e+09"},
+    {0x1.240cf8p+32f, chars_format::scientific, 9, "4.899796992e+09"},
+    {0x1.81669ap+33f, chars_format::scientific, 10, "1.2931904512e+10"},
+    {0x1.3be30cp+34f, chars_format::scientific, 10, "2.1198811136e+10"},
+    {0x1.d1e6e4p+35f, chars_format::scientific, 10, "6.2532296704e+10"},
+    {0x1.06b274p+36f, chars_format::scientific, 10, "7.0517211136e+10"},
+    {0x1.a74284p+37f, chars_format::scientific, 11, "2.27235889152e+11"},
+    {0x1.9fd3e6p+38f, chars_format::scientific, 11, "4.46491623424e+11"},
+    {0x1.e2cec4p+39f, chars_format::scientific, 12, "1.036821594112e+12"},
+    {0x1.3d5d32p+40f, chars_format::scientific, 11, "1.36306819072e+12"},
+    {0x1.accccap+41f, chars_format::scientific, 12, "3.683363586048e+12"},
+    {0x1.a120ccp+42f, chars_format::scientific, 12, "7.166206410752e+12"},
+    {0x1.55a028p+43f, chars_format::scientific, 13, "1.1738166591488e+13"},
+    {0x1.035296p+44f, chars_format::scientific, 13, "1.7820513468416e+13"},
+    {0x1.22d1aap+45f, chars_format::scientific, 13, "3.9969859043328e+13"},
+    {0x1.eb8eaep+46f, chars_format::scientific, 14, "1.35118253457408e+14"},
+    {0x1.490d0ep+47f, chars_format::scientific, 14, "1.80897697497088e+14"},
+    {0x1.9da088p+48f, chars_format::scientific, 14, "4.54787778740224e+14"},
+    {0x1.e7fab4p+49f, chars_format::scientific, 15, "1.073077848899584e+15"},
+    {0x1.98a534p+50f, chars_format::scientific, 14, "1.79724114460672e+15"},
+    {0x1.93aeeap+51f, chars_format::scientific, 15, "3.550835489374208e+15"},
+    {0x1.3df680p+52f, chars_format::scientific, 15, "5.593662327095296e+15"},
+    {0x1.c763f6p+53f, chars_format::scientific, 15, "1.602262782705664e+16"},
+    {0x1.8b669ep+54f, chars_format::scientific, 15, "2.782386114789376e+16"},
+    {0x1.73e5b6p+55f, chars_format::scientific, 16, "5.2339893103230976e+16"},
+    {0x1.a13d18p+56f, chars_format::scientific, 17, "1.17442238576852992e+17"},
+    {0x1.a0797ep+57f, chars_format::scientific, 17, "2.34454344768946176e+17"},
+    {0x1.c07a80p+58f, chars_format::scientific, 17, "5.04941918963105792e+17"},
+    {0x1.729388p+59f, chars_format::scientific, 17, "8.34463629662224384e+17"},
+    {0x1.edfb70p+60f, chars_format::scientific, 18, "2.224697951572197376e+18"},
+    {0x1.3d6782p+61f, chars_format::scientific, 17, "2.85892402114199552e+18"},
+    {0x1.b121e8p+62f, chars_format::scientific, 18, "7.802620494837972992e+18"},
+    {0x1.0efc5ap+63f, chars_format::scientific, 18, "9.763290520209063936e+18"},
+    {0x1.b7dba0p+64f, chars_format::scientific, 19, "3.1695102724410441728e+19"},
+    {0x1.ec2306p+65f, chars_format::scientific, 19, "7.0924388975830368256e+19"},
+    {0x1.2e2d28p+66f, chars_format::scientific, 19, "8.7096415015485308928e+19"},
+    {0x1.e02208p+67f, chars_format::scientific, 20, "2.76777792668052750336e+20"},
+    {0x1.402636p+68f, chars_format::scientific, 20, "3.69106968238077509632e+20"},
+    {0x1.11f97cp+69f, chars_format::scientific, 20, "6.31742296991907971072e+20"},
+    {0x1.74db2ap+70f, chars_format::scientific, 21, "1.719495307615820316672e+21"},
+    {0x1.94a32ap+71f, chars_format::scientific, 21, "3.732120907777931476992e+21"},
+    {0x1.c272dcp+72f, chars_format::scientific, 21, "8.309311323384498356224e+21"},
+    {0x1.36ca40p+73f, chars_format::scientific, 22, "1.1466128622488263852032e+22"},
+    {0x1.5f6fbep+74f, chars_format::scientific, 22, "2.5931436172223350571008e+22"},
+    {0x1.95ec4ep+75f, chars_format::scientific, 22, "5.9903671176748022628352e+22"},
+    {0x1.6b3912p+76f, chars_format::scientific, 23, "1.07204487170660958732288e+23"},
+    {0x1.10992ap+77f, chars_format::scientific, 23, "1.60913632700346331561984e+23"},
+    {0x1.74a25ep+78f, chars_format::scientific, 23, "4.39928869395322133020672e+23"},
+    {0x1.43f462p+79f, chars_format::scientific, 22, "7.6491622058254812577792e+23"},
+    {0x1.f12ca2p+80f, chars_format::scientific, 24, "2.347839472055691035803648e+24"},
+    {0x1.2b7f18p+81f, chars_format::scientific, 22, "2.8286640885152838844416e+24"},
+    {0x1.a40704p+82f, chars_format::scientific, 24, "7.934093352976572433301504e+24"},
+    {0x1.35d5f8p+83f, chars_format::scientific, 23, "1.17052661598219352932352e+25"},
+    {0x1.c2c9d2p+84f, chars_format::scientific, 25, "3.4060605519118462894473216e+25"},
+    {0x1.47bf20p+85f, chars_format::scientific, 23, "4.95276631635027751337984e+25"},
+    {0x1.60b728p+86f, chars_format::scientific, 25, "1.0660170486011939073818624e+26"},
+    {0x1.3354c8p+87f, chars_format::scientific, 26, "1.85770297377533474371534848e+26"},
+    {0x1.e9e512p+88f, chars_format::scientific, 26, "5.92246479757524141957185536e+26"},
+    {0x1.c4b6cap+89f, chars_format::scientific, 27, "1.094595334815995103451021312e+27"},
+    {0x1.799cb8p+90f, chars_format::scientific, 27, "1.826020469467809704300249088e+27"},
+    {0x1.1afa36p+91f, chars_format::scientific, 27, "2.736789351009782551090823168e+27"},
+    {0x1.80c214p+92f, chars_format::scientific, 27, "7.442304364233212615194574848e+27"},
+    {0x1.657890p+93f, chars_format::scientific, 28, "1.3828987453168434783077793792e+28"},
+    {0x1.5ce17cp+94f, chars_format::scientific, 28, "2.6993344325171312829134798848e+28"},
+    {0x1.3f1e9ap+95f, chars_format::scientific, 28, "4.9381356576017938861904625664e+28"},
+    {0x1.874612p+96f, chars_format::scientific, 29, "1.21093348650115637567232671744e+29"},
+    {0x1.5f4d5ep+97f, chars_format::scientific, 29, "2.17445539275703670631001227264e+29"},
+    {0x1.45b1bep+98f, chars_format::scientific, 29, "4.03190021246562727728269754368e+29"},
+    {0x1.a570f4p+99f, chars_format::scientific, 30, "1.043437928672039460753056464896e+30"},
+    {0x1.f5106ep+100f, chars_format::scientific, 30, "2.481149635102733266542145830912e+30"},
+    {0x1.d84424p+101f, chars_format::scientific, 30, "4.677097651091265616934539886592e+30"},
+    {0x1.3d6c56p+102f, chars_format::scientific, 30, "6.287213966425746785671183335424e+30"},
+    {0x1.9d8cf0p+103f, chars_format::scientific, 31, "1.6382424580981433623378525159424e+31"},
+    {0x1.e2e73ep+104f, chars_format::scientific, 29, "3.82595403225449575379724402688e+31"},
+    {0x1.2d6594p+105f, chars_format::scientific, 30, "4.775822764761364886543157690368e+31"},
+    {0x1.ce43bap+106f, chars_format::scientific, 31, "1.4649748574980240963539344293888e+32"},
+    {0x1.b3ea00p+107f, chars_format::scientific, 32, "2.76293361488025452794185737306112e+32"},
+    {0x1.03a052p+108f, chars_format::scientific, 32, "3.29115373194929392757058784198656e+32"},
+    {0x1.6f59e0p+109f, chars_format::scientific, 31, "9.3134561945576656911623262306304e+32"},
+    {0x1.05adacp+110f, chars_format::scientific, 33, "1.326867152522435745601434087849984e+33"},
+    {0x1.2cdef0p+111f, chars_format::scientific, 33, "3.051192904788012466473218045116416e+33"},
+    {0x1.e81552p+112f, chars_format::scientific, 33, "9.899505055765620068271358482579456e+33"},
+    {0x1.bfa8f4p+113f, chars_format::scientific, 34, "1.8159245876954178992833811110166528e+34"},
+    {0x1.a14810p+114f, chars_format::scientific, 33, "3.385389673673572296245535418875904e+34"},
+    {0x1.f18b10p+115f, chars_format::scientific, 34, "8.0731001914916160681187088757948416e+34"},
+    {0x1.8d6e30p+116f, chars_format::scientific, 32, "1.28973545052908058560090358153216e+35"},
+    {0x1.9480c2p+117f, chars_format::scientific, 35, "2.62537431192608192877759864086986752e+35"},
+    {0x1.60975cp+118f, chars_format::scientific, 34, "4.5768960676134050994895233721827328e+35"},
+    {0x1.ab1bb2p+119f, chars_format::scientific, 36, "1.108836243133298765768030079592431616e+36"},
+    {0x1.6a0c80p+120f, chars_format::scientific, 36, "1.879864992909653247408339011818749952e+36"},
+    {0x1.2cac2cp+121f, chars_format::scientific, 36, "3.122362236102854007005843883842076672e+36"},
+    {0x1.0baaf6p+122f, chars_format::scientific, 36, "5.559243043957593079267046257728684032e+36"},
+    {0x1.098282p+123f, chars_format::scientific, 35, "1.10288454433706471446366546449924096e+37"},
+    {0x1.122f8ap+124f, chars_format::scientific, 37, "2.2778456735621461875293910785310326784e+37"},
+    {0x1.57f4c6p+125f, chars_format::scientific, 36, "5.714951736310127067226390054203031552e+37"},
+    {0x1.05e028p+126f, chars_format::scientific, 36, "8.702309817313974757087535795024166912e+37"},
+    {0x1.9d8424p+127f, chars_format::scientific, 38, "2.74828637805621292108186801756142829568e+38"},
+
+    // Ryu Printf PrintDecimalPoint
+    // These values exercise each codepath.
+    {0x1.59bc8cp+92f, chars_format::scientific, 0, "7e+27"},
+    {0x1.59bc8cp+92f, chars_format::scientific, 1, "6.7e+27"},
+    {0x1.37da7cp-30f, chars_format::scientific, 0, "1e-09"},
+    {0x1.37da7cp-30f, chars_format::scientific, 1, "1.1e-09"},
+    {0x1.834c98p+29f, chars_format::scientific, 0, "8e+08"},
+    {0x1.834c98p+29f, chars_format::scientific, 1, "8.1e+08"},
+
+    // Test the maximum mantissa, which generates the most digits for each exponent.
+    {0x0.fffffep-126f, chars_format::scientific, 111,
+        "1."
+        "1754942106924410754870294448492873488270524287458933338571745305715888704756189042655023513361811637878417"
+        "96875e-38"},
+    {0x1.fffffep-126f, chars_format::scientific, 111,
+        "2."
+        "3509885615147285834557659820715330266457179855179808553659262368500061299303460771170648513361811637878417"
+        "96875e-38"},
+    {0x1.fffffep-125f, chars_format::scientific, 110,
+        "4."
+        "7019771230294571669115319641430660532914359710359617107318524737000122598606921542341297026723623275756835"
+        "9375e-38"},
+    {0x1.fffffep-124f, chars_format::scientific, 109,
+        "9."
+        "4039542460589143338230639282861321065828719420719234214637049474000245197213843084682594053447246551513671"
+        "875e-38"},
+    {0x1.fffffep-123f, chars_format::scientific, 109,
+        "1."
+        "8807908492117828667646127856572264213165743884143846842927409894800049039442768616936518810689449310302734"
+        "375e-37"},
+    {0x1.fffffep-122f, chars_format::scientific, 108,
+        "3."
+        "7615816984235657335292255713144528426331487768287693685854819789600098078885537233873037621378898620605468"
+        "75e-37"},
+    {0x1.fffffep-121f, chars_format::scientific, 107,
+        "7."
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+    {0x1.fffffep+16f, chars_format::scientific, 12, "1.310719921875e+05"},
+    {0x1.fffffep+17f, chars_format::scientific, 11, "2.62143984375e+05"},
+    {0x1.fffffep+18f, chars_format::scientific, 10, "5.2428796875e+05"},
+    {0x1.fffffep+19f, chars_format::scientific, 10, "1.0485759375e+06"},
+    {0x1.fffffep+20f, chars_format::scientific, 9, "2.097151875e+06"},
+    {0x1.fffffep+21f, chars_format::scientific, 8, "4.19430375e+06"},
+    {0x1.fffffep+22f, chars_format::scientific, 7, "8.3886075e+06"},
+    {0x1.fffffep+23f, chars_format::scientific, 7, "1.6777215e+07"},
+    {0x1.fffffep+24f, chars_format::scientific, 6, "3.355443e+07"},
+    {0x1.fffffep+25f, chars_format::scientific, 6, "6.710886e+07"},
+    {0x1.fffffep+26f, chars_format::scientific, 7, "1.3421772e+08"},
+    {0x1.fffffep+27f, chars_format::scientific, 7, "2.6843544e+08"},
+    {0x1.fffffep+28f, chars_format::scientific, 7, "5.3687088e+08"},
+    {0x1.fffffep+29f, chars_format::scientific, 8, "1.07374176e+09"},
+    {0x1.fffffep+30f, chars_format::scientific, 8, "2.14748352e+09"},
+    {0x1.fffffep+31f, chars_format::scientific, 8, "4.29496704e+09"},
+    {0x1.fffffep+32f, chars_format::scientific, 8, "8.58993408e+09"},
+    {0x1.fffffep+33f, chars_format::scientific, 9, "1.717986816e+10"},
+    {0x1.fffffep+34f, chars_format::scientific, 9, "3.435973632e+10"},
+    {0x1.fffffep+35f, chars_format::scientific, 9, "6.871947264e+10"},
+    {0x1.fffffep+36f, chars_format::scientific, 10, "1.3743894528e+11"},
+    {0x1.fffffep+37f, chars_format::scientific, 10, "2.7487789056e+11"},
+    {0x1.fffffep+38f, chars_format::scientific, 10, "5.4975578112e+11"},
+    {0x1.fffffep+39f, chars_format::scientific, 11, "1.09951156224e+12"},
+    {0x1.fffffep+40f, chars_format::scientific, 11, "2.19902312448e+12"},
+    {0x1.fffffep+41f, chars_format::scientific, 11, "4.39804624896e+12"},
+    {0x1.fffffep+42f, chars_format::scientific, 11, "8.79609249792e+12"},
+    {0x1.fffffep+43f, chars_format::scientific, 12, "1.759218499584e+13"},
+    {0x1.fffffep+44f, chars_format::scientific, 12, "3.518436999168e+13"},
+    {0x1.fffffep+45f, chars_format::scientific, 12, "7.036873998336e+13"},
+    {0x1.fffffep+46f, chars_format::scientific, 13, "1.4073747996672e+14"},
+    {0x1.fffffep+47f, chars_format::scientific, 13, "2.8147495993344e+14"},
+    {0x1.fffffep+48f, chars_format::scientific, 13, "5.6294991986688e+14"},
+    {0x1.fffffep+49f, chars_format::scientific, 14, "1.12589983973376e+15"},
+    {0x1.fffffep+50f, chars_format::scientific, 14, "2.25179967946752e+15"},
+    {0x1.fffffep+51f, chars_format::scientific, 14, "4.50359935893504e+15"},
+    {0x1.fffffep+52f, chars_format::scientific, 14, "9.00719871787008e+15"},
+    {0x1.fffffep+53f, chars_format::scientific, 15, "1.801439743574016e+16"},
+    {0x1.fffffep+54f, chars_format::scientific, 15, "3.602879487148032e+16"},
+    {0x1.fffffep+55f, chars_format::scientific, 15, "7.205758974296064e+16"},
+    {0x1.fffffep+56f, chars_format::scientific, 16, "1.4411517948592128e+17"},
+    {0x1.fffffep+57f, chars_format::scientific, 16, "2.8823035897184256e+17"},
+    {0x1.fffffep+58f, chars_format::scientific, 16, "5.7646071794368512e+17"},
+    {0x1.fffffep+59f, chars_format::scientific, 17, "1.15292143588737024e+18"},
+    {0x1.fffffep+60f, chars_format::scientific, 17, "2.30584287177474048e+18"},
+    {0x1.fffffep+61f, chars_format::scientific, 17, "4.61168574354948096e+18"},
+    {0x1.fffffep+62f, chars_format::scientific, 17, "9.22337148709896192e+18"},
+    {0x1.fffffep+63f, chars_format::scientific, 18, "1.844674297419792384e+19"},
+    {0x1.fffffep+64f, chars_format::scientific, 18, "3.689348594839584768e+19"},
+    {0x1.fffffep+65f, chars_format::scientific, 18, "7.378697189679169536e+19"},
+    {0x1.fffffep+66f, chars_format::scientific, 19, "1.4757394379358339072e+20"},
+    {0x1.fffffep+67f, chars_format::scientific, 19, "2.9514788758716678144e+20"},
+    {0x1.fffffep+68f, chars_format::scientific, 19, "5.9029577517433356288e+20"},
+    {0x1.fffffep+69f, chars_format::scientific, 20, "1.18059155034866712576e+21"},
+    {0x1.fffffep+70f, chars_format::scientific, 20, "2.36118310069733425152e+21"},
+    {0x1.fffffep+71f, chars_format::scientific, 20, "4.72236620139466850304e+21"},
+    {0x1.fffffep+72f, chars_format::scientific, 20, "9.44473240278933700608e+21"},
+    {0x1.fffffep+73f, chars_format::scientific, 21, "1.888946480557867401216e+22"},
+    {0x1.fffffep+74f, chars_format::scientific, 21, "3.777892961115734802432e+22"},
+    {0x1.fffffep+75f, chars_format::scientific, 21, "7.555785922231469604864e+22"},
+    {0x1.fffffep+76f, chars_format::scientific, 22, "1.5111571844462939209728e+23"},
+    {0x1.fffffep+77f, chars_format::scientific, 22, "3.0223143688925878419456e+23"},
+    {0x1.fffffep+78f, chars_format::scientific, 22, "6.0446287377851756838912e+23"},
+    {0x1.fffffep+79f, chars_format::scientific, 23, "1.20892574755703513677824e+24"},
+    {0x1.fffffep+80f, chars_format::scientific, 23, "2.41785149511407027355648e+24"},
+    {0x1.fffffep+81f, chars_format::scientific, 23, "4.83570299022814054711296e+24"},
+    {0x1.fffffep+82f, chars_format::scientific, 23, "9.67140598045628109422592e+24"},
+    {0x1.fffffep+83f, chars_format::scientific, 24, "1.934281196091256218845184e+25"},
+    {0x1.fffffep+84f, chars_format::scientific, 24, "3.868562392182512437690368e+25"},
+    {0x1.fffffep+85f, chars_format::scientific, 24, "7.737124784365024875380736e+25"},
+    {0x1.fffffep+86f, chars_format::scientific, 25, "1.5474249568730049750761472e+26"},
+    {0x1.fffffep+87f, chars_format::scientific, 25, "3.0948499137460099501522944e+26"},
+    {0x1.fffffep+88f, chars_format::scientific, 25, "6.1896998274920199003045888e+26"},
+    {0x1.fffffep+89f, chars_format::scientific, 26, "1.23793996549840398006091776e+27"},
+    {0x1.fffffep+90f, chars_format::scientific, 26, "2.47587993099680796012183552e+27"},
+    {0x1.fffffep+91f, chars_format::scientific, 26, "4.95175986199361592024367104e+27"},
+    {0x1.fffffep+92f, chars_format::scientific, 26, "9.90351972398723184048734208e+27"},
+    {0x1.fffffep+93f, chars_format::scientific, 27, "1.980703944797446368097468416e+28"},
+    {0x1.fffffep+94f, chars_format::scientific, 27, "3.961407889594892736194936832e+28"},
+    {0x1.fffffep+95f, chars_format::scientific, 27, "7.922815779189785472389873664e+28"},
+    {0x1.fffffep+96f, chars_format::scientific, 28, "1.5845631558379570944779747328e+29"},
+    {0x1.fffffep+97f, chars_format::scientific, 28, "3.1691263116759141889559494656e+29"},
+    {0x1.fffffep+98f, chars_format::scientific, 28, "6.3382526233518283779118989312e+29"},
+    {0x1.fffffep+99f, chars_format::scientific, 29, "1.26765052467036567558237978624e+30"},
+    {0x1.fffffep+100f, chars_format::scientific, 29, "2.53530104934073135116475957248e+30"},
+    {0x1.fffffep+101f, chars_format::scientific, 29, "5.07060209868146270232951914496e+30"},
+    {0x1.fffffep+102f, chars_format::scientific, 30, "1.014120419736292540465903828992e+31"},
+    {0x1.fffffep+103f, chars_format::scientific, 30, "2.028240839472585080931807657984e+31"},
+    {0x1.fffffep+104f, chars_format::scientific, 30, "4.056481678945170161863615315968e+31"},
+    {0x1.fffffep+105f, chars_format::scientific, 30, "8.112963357890340323727230631936e+31"},
+    {0x1.fffffep+106f, chars_format::scientific, 31, "1.6225926715780680647454461263872e+32"},
+    {0x1.fffffep+107f, chars_format::scientific, 31, "3.2451853431561361294908922527744e+32"},
+    {0x1.fffffep+108f, chars_format::scientific, 31, "6.4903706863122722589817845055488e+32"},
+    {0x1.fffffep+109f, chars_format::scientific, 32, "1.29807413726245445179635690110976e+33"},
+    {0x1.fffffep+110f, chars_format::scientific, 32, "2.59614827452490890359271380221952e+33"},
+    {0x1.fffffep+111f, chars_format::scientific, 32, "5.19229654904981780718542760443904e+33"},
+    {0x1.fffffep+112f, chars_format::scientific, 33, "1.038459309809963561437085520887808e+34"},
+    {0x1.fffffep+113f, chars_format::scientific, 33, "2.076918619619927122874171041775616e+34"},
+    {0x1.fffffep+114f, chars_format::scientific, 33, "4.153837239239854245748342083551232e+34"},
+    {0x1.fffffep+115f, chars_format::scientific, 33, "8.307674478479708491496684167102464e+34"},
+    {0x1.fffffep+116f, chars_format::scientific, 34, "1.6615348956959416982993368334204928e+35"},
+    {0x1.fffffep+117f, chars_format::scientific, 34, "3.3230697913918833965986736668409856e+35"},
+    {0x1.fffffep+118f, chars_format::scientific, 34, "6.6461395827837667931973473336819712e+35"},
+    {0x1.fffffep+119f, chars_format::scientific, 35, "1.32922791655675335863946946673639424e+36"},
+    {0x1.fffffep+120f, chars_format::scientific, 35, "2.65845583311350671727893893347278848e+36"},
+    {0x1.fffffep+121f, chars_format::scientific, 35, "5.31691166622701343455787786694557696e+36"},
+    {0x1.fffffep+122f, chars_format::scientific, 36, "1.063382333245402686911575573389115392e+37"},
+    {0x1.fffffep+123f, chars_format::scientific, 36, "2.126764666490805373823151146778230784e+37"},
+    {0x1.fffffep+124f, chars_format::scientific, 36, "4.253529332981610747646302293556461568e+37"},
+    {0x1.fffffep+125f, chars_format::scientific, 36, "8.507058665963221495292604587112923136e+37"},
+    {0x1.fffffep+126f, chars_format::scientific, 37, "1.7014117331926442990585209174225846272e+38"},
+    {0x1.fffffep+127f, chars_format::scientific, 37, "3.4028234663852885981170418348451692544e+38"},
+};
+
+#endif // FLOAT_SCIENTIFIC_PRECISION_TO_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/float_to_chars_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+
+// Copyright 2018 Ulf Adams
+// Copyright (c) Microsoft Corporation. All rights reserved.
+
+// Boost Software License - Version 1.0 - August 17th, 2003
+
+// Permission is hereby granted, free of charge, to any person or organization
+// obtaining a copy of the software and accompanying documentation covered by
+// this license (the "Software") to use, reproduce, display, distribute,
+// execute, and transmit the Software, and to prepare derivative works of the
+// Software, and to permit third-parties to whom the Software is furnished to
+// do so, all subject to the following:
+
+// The copyright notices in the Software and this entire statement, including
+// the above license grant, this restriction and the following disclaimer,
+// must be included in all copies of the Software, in whole or in part, and
+// all derivative works of the Software, unless such copies or derivative
+// works are solely in the form of machine-executable object code generated by
+// a source language processor.
+
+// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
+// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
+// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
+// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
+// DEALINGS IN THE SOFTWARE.
+
+
+// This file contains test cases derived from:
+// https://github.com/ulfjack/ryu
+// See xcharconv_ryu.h for the exact commit.
+// (Keep the cgmanifest.json commitHash in sync.)
+
+
+#ifndef FLOAT_TO_CHARS_TEST_CASES_HPP
+#define FLOAT_TO_CHARS_TEST_CASES_HPP
+
+#include <charconv>
+
+#include "test.hpp"
+using namespace std;
+
+inline constexpr FloatToCharsTestCase float_to_chars_test_cases[] = {
+    // Test special cases (zero, inf, nan) and an ordinary case. Also test negative signs.
+    {0.0f, chars_format::scientific, "0e+00"},
+    {-0.0f, chars_format::scientific, "-0e+00"},
+    {float_inf, chars_format::scientific, "inf"},
+    {-float_inf, chars_format::scientific, "-inf"},
+    {float_nan, chars_format::scientific, "nan"},
+    {-float_nan, chars_format::scientific, "-nan(ind)"},
+    {float_nan_payload, chars_format::scientific, "nan"},
+    {-float_nan_payload, chars_format::scientific, "-nan"},
+    {2.018f, chars_format::scientific, "2.018e+00"},
+    {-2.018f, chars_format::scientific, "-2.018e+00"},
+
+    // Ditto for fixed, which doesn't emit exponents.
+    {0.0f, chars_format::fixed, "0"},
+    {-0.0f, chars_format::fixed, "-0"},
+    {float_inf, chars_format::fixed, "inf"},
+    {-float_inf, chars_format::fixed, "-inf"},
+    {float_nan, chars_format::fixed, "nan"},
+    {-float_nan, chars_format::fixed, "-nan(ind)"},
+    {float_nan_payload, chars_format::fixed, "nan"},
+    {-float_nan_payload, chars_format::fixed, "-nan"},
+    {2.018f, chars_format::fixed, "2.018"},
+    {-2.018f, chars_format::fixed, "-2.018"},
+
+    // Ditto for general, which selects fixed for the scientific exponent 0.
+    {0.0f, chars_format::general, "0"},
+    {-0.0f, chars_format::general, "-0"},
+    {float_inf, chars_format::general, "inf"},
+    {-float_inf, chars_format::general, "-inf"},
+    {float_nan, chars_format::general, "nan"},
+    {-float_nan, chars_format::general, "-nan(ind)"},
+    {float_nan_payload, chars_format::general, "nan"},
+    {-float_nan_payload, chars_format::general, "-nan"},
+    {2.018f, chars_format::general, "2.018"},
+    {-2.018f, chars_format::general, "-2.018"},
+
+    // Ditto for plain, which selects fixed because it's shorter for these values.
+    {0.0f, chars_format{}, "0"},
+    {-0.0f, chars_format{}, "-0"},
+    {float_inf, chars_format{}, "inf"},
+    {-float_inf, chars_format{}, "-inf"},
+    {float_nan, chars_format{}, "nan"},
+    {-float_nan, chars_format{}, "-nan(ind)"},
+    {float_nan_payload, chars_format{}, "nan"},
+    {-float_nan_payload, chars_format{}, "-nan"},
+    {2.018f, chars_format{}, "2.018"},
+    {-2.018f, chars_format{}, "-2.018"},
+
+    // Ditto for hex.
+    {0.0f, chars_format::hex, "0p+0"},
+    {-0.0f, chars_format::hex, "-0p+0"},
+    {float_inf, chars_format::hex, "inf"},
+    {-float_inf, chars_format::hex, "-inf"},
+    {float_nan, chars_format::hex, "nan"},
+    {-float_nan, chars_format::hex, "-nan(ind)"},
+    {float_nan_payload, chars_format::hex, "nan"},
+    {-float_nan_payload, chars_format::hex, "-nan"},
+    {0x1.729p+0f, chars_format::hex, "1.729p+0"},
+    {-0x1.729p+0f, chars_format::hex, "-1.729p+0"},
+
+    // Ryu f2s_test.cc SwitchToSubnormal
+    {1.1754944e-38f, chars_format::scientific, "1.1754944e-38"},
+
+    // Ryu f2s_test.cc MinAndMax
+    {0x1.fffffep+127f, chars_format::scientific, "3.4028235e+38"},
+    {0x1.000000p-149f, chars_format::scientific, "1e-45"},
+
+    // Ryu f2s_test.cc BoundaryRoundEven
+    {3.355445e7f, chars_format::scientific, "3.355445e+07"},
+    {8.999999e9f, chars_format::scientific, "9e+09"},
+    {3.4366717e10f, chars_format::scientific, "3.436672e+10"},
+
+    // Ryu f2s_test.cc ExactValueRoundEven
+    {3.0540412e5f, chars_format::scientific, "3.0540412e+05"},
+    {8.0990312e3f, chars_format::scientific, "8.0990312e+03"},
+
+    // Ryu f2s_test.cc LotsOfTrailingZeros
+    {2.4414062e-4f, chars_format::scientific, "2.4414062e-04"},
+    {2.4414062e-3f, chars_format::scientific, "2.4414062e-03"},
+    {4.3945312e-3f, chars_format::scientific, "4.3945312e-03"},
+    {6.3476562e-3f, chars_format::scientific, "6.3476562e-03"},
+
+    // Ryu f2s_test.cc Regression
+    {4.7223665e21f, chars_format::scientific, "4.7223665e+21"},
+    {8388608.0f, chars_format::scientific, "8.388608e+06"},
+    {1.6777216e7f, chars_format::scientific, "1.6777216e+07"},
+    {3.3554436e7f, chars_format::scientific, "3.3554436e+07"},
+    {6.7131496e7f, chars_format::scientific, "6.7131496e+07"},
+    {1.9310392e-38f, chars_format::scientific, "1.9310392e-38"},
+    {-2.47e-43f, chars_format::scientific, "-2.47e-43"},
+    {1.993244e-38f, chars_format::scientific, "1.993244e-38"},
+    {4103.9003f, chars_format::scientific, "4.1039004e+03"},
+    {5.3399997e9f, chars_format::scientific, "5.3399997e+09"},
+    {6.0898e-39f, chars_format::scientific, "6.0898e-39"},
+    {0.0010310042f, chars_format::scientific, "1.0310042e-03"},
+    {2.8823261e17f, chars_format::scientific, "2.882326e+17"},
+    {0x1.5c87fap-84f, chars_format::scientific, "7.038531e-26"}, // TRANSITION, VSO-629490, should be 7.038531e-26f
+    {9.2234038e17f, chars_format::scientific, "9.223404e+17"},
+    {6.7108872e7f, chars_format::scientific, "6.710887e+07"},
+    {1.0e-44f, chars_format::scientific, "1e-44"},
+    {2.816025e14f, chars_format::scientific, "2.816025e+14"},
+    {9.223372e18f, chars_format::scientific, "9.223372e+18"},
+    {1.5846085e29f, chars_format::scientific, "1.5846086e+29"},
+    {1.1811161e19f, chars_format::scientific, "1.1811161e+19"},
+    {5.368709e18f, chars_format::scientific, "5.368709e+18"},
+    {4.6143165e18f, chars_format::scientific, "4.6143166e+18"},
+    {0.007812537f, chars_format::scientific, "7.812537e-03"},
+    {1.4e-45f, chars_format::scientific, "1e-45"},
+    {1.18697724e20f, chars_format::scientific, "1.18697725e+20"},
+    {1.00014165e-36f, chars_format::scientific, "1.00014165e-36"},
+    {200.0f, chars_format::scientific, "2e+02"},
+    {3.3554432e7f, chars_format::scientific, "3.3554432e+07"},
+
+    // Ryu f2s_test.cc LooksLikePow5
+    {0x1.2a05f2p+59f, chars_format::scientific, "6.7108864e+17"},
+    {0x1.2a05f2p+60f, chars_format::scientific, "1.3421773e+18"},
+    {0x1.2a05f2p+61f, chars_format::scientific, "2.6843546e+18"},
+
+    // Ryu f2s_test.cc OutputLength
+    {1.0f, chars_format::scientific, "1e+00"},
+    {1.2f, chars_format::scientific, "1.2e+00"},
+    {1.23f, chars_format::scientific, "1.23e+00"},
+    {1.234f, chars_format::scientific, "1.234e+00"},
+    {1.2345f, chars_format::scientific, "1.2345e+00"},
+    {1.23456f, chars_format::scientific, "1.23456e+00"},
+    {1.234567f, chars_format::scientific, "1.234567e+00"},
+    {1.2345678f, chars_format::scientific, "1.2345678e+00"},
+    {1.23456735e-36f, chars_format::scientific, "1.23456735e-36"},
+
+    // Test all exponents.
+    {1.729e-45f, chars_format::scientific, "1e-45"},
+    {1.729e-44f, chars_format::scientific, "1.7e-44"},
+    {1.729e-43f, chars_format::scientific, "1.72e-43"},
+    {1.729e-42f, chars_format::scientific, "1.729e-42"},
+    {1.729e-41f, chars_format::scientific, "1.729e-41"},
+    {1.729e-40f, chars_format::scientific, "1.729e-40"},
+    {1.729e-39f, chars_format::scientific, "1.729e-39"},
+    {1.729e-38f, chars_format::scientific, "1.729e-38"},
+    {1.729e-37f, chars_format::scientific, "1.729e-37"},
+    {1.729e-36f, chars_format::scientific, "1.729e-36"},
+    {1.729e-35f, chars_format::scientific, "1.729e-35"},
+    {1.729e-34f, chars_format::scientific, "1.729e-34"},
+    {1.729e-33f, chars_format::scientific, "1.729e-33"},
+    {1.729e-32f, chars_format::scientific, "1.729e-32"},
+    {1.729e-31f, chars_format::scientific, "1.729e-31"},
+    {1.729e-30f, chars_format::scientific, "1.729e-30"},
+    {1.729e-29f, chars_format::scientific, "1.729e-29"},
+    {1.729e-28f, chars_format::scientific, "1.729e-28"},
+    {1.729e-27f, chars_format::scientific, "1.729e-27"},
+    {1.729e-26f, chars_format::scientific, "1.729e-26"},
+    {1.729e-25f, chars_format::scientific, "1.729e-25"},
+    {1.729e-24f, chars_format::scientific, "1.729e-24"},
+    {1.729e-23f, chars_format::scientific, "1.729e-23"},
+    {1.729e-22f, chars_format::scientific, "1.729e-22"},
+    {1.729e-21f, chars_format::scientific, "1.729e-21"},
+    {1.729e-20f, chars_format::scientific, "1.729e-20"},
+    {1.729e-19f, chars_format::scientific, "1.729e-19"},
+    {1.729e-18f, chars_format::scientific, "1.729e-18"},
+    {1.729e-17f, chars_format::scientific, "1.729e-17"},
+    {1.729e-16f, chars_format::scientific, "1.729e-16"},
+    {1.729e-15f, chars_format::scientific, "1.729e-15"},
+    {1.729e-14f, chars_format::scientific, "1.729e-14"},
+    {1.729e-13f, chars_format::scientific, "1.729e-13"},
+    {1.729e-12f, chars_format::scientific, "1.729e-12"},
+    {1.729e-11f, chars_format::scientific, "1.729e-11"},
+    {1.729e-10f, chars_format::scientific, "1.729e-10"},
+    {1.729e-9f, chars_format::scientific, "1.729e-09"},
+    {1.729e-8f, chars_format::scientific, "1.729e-08"},
+    {1.729e-7f, chars_format::scientific, "1.729e-07"},
+    {1.729e-6f, chars_format::scientific, "1.729e-06"},
+    {1.729e-5f, chars_format::scientific, "1.729e-05"},
+    {1.729e-4f, chars_format::scientific, "1.729e-04"},
+    {1.729e-3f, chars_format::scientific, "1.729e-03"},
+    {1.729e-2f, chars_format::scientific, "1.729e-02"},
+    {1.729e-1f, chars_format::scientific, "1.729e-01"},
+    {1.729e0f, chars_format::scientific, "1.729e+00"},
+    {1.729e1f, chars_format::scientific, "1.729e+01"},
+    {1.729e2f, chars_format::scientific, "1.729e+02"},
+    {1.729e3f, chars_format::scientific, "1.729e+03"},
+    {1.729e4f, chars_format::scientific, "1.729e+04"},
+    {1.729e5f, chars_format::scientific, "1.729e+05"},
+    {1.729e6f, chars_format::scientific, "1.729e+06"},
+    {1.729e7f, chars_format::scientific, "1.729e+07"},
+    {1.729e8f, chars_format::scientific, "1.729e+08"},
+    {1.729e9f, chars_format::scientific, "1.729e+09"},
+    {1.729e10f, chars_format::scientific, "1.729e+10"},
+    {1.729e11f, chars_format::scientific, "1.729e+11"},
+    {1.729e12f, chars_format::scientific, "1.729e+12"},
+    {1.729e13f, chars_format::scientific, "1.729e+13"},
+    {1.729e14f, chars_format::scientific, "1.729e+14"},
+    {1.729e15f, chars_format::scientific, "1.729e+15"},
+    {1.729e16f, chars_format::scientific, "1.729e+16"},
+    {1.729e17f, chars_format::scientific, "1.729e+17"},
+    {1.729e18f, chars_format::scientific, "1.729e+18"},
+    {1.729e19f, chars_format::scientific, "1.729e+19"},
+    {1.729e20f, chars_format::scientific, "1.729e+20"},
+    {1.729e21f, chars_format::scientific, "1.729e+21"},
+    {1.729e22f, chars_format::scientific, "1.729e+22"},
+    {1.729e23f, chars_format::scientific, "1.729e+23"},
+    {1.729e24f, chars_format::scientific, "1.729e+24"},
+    {1.729e25f, chars_format::scientific, "1.729e+25"},
+    {1.729e26f, chars_format::scientific, "1.729e+26"},
+    {1.729e27f, chars_format::scientific, "1.729e+27"},
+    {1.729e28f, chars_format::scientific, "1.729e+28"},
+    {1.729e29f, chars_format::scientific, "1.729e+29"},
+    {1.729e30f, chars_format::scientific, "1.729e+30"},
+    {1.729e31f, chars_format::scientific, "1.729e+31"},
+    {1.729e32f, chars_format::scientific, "1.729e+32"},
+    {1.729e33f, chars_format::scientific, "1.729e+33"},
+    {1.729e34f, chars_format::scientific, "1.729e+34"},
+    {1.729e35f, chars_format::scientific, "1.729e+35"},
+    {1.729e36f, chars_format::scientific, "1.729e+36"},
+    {1.729e37f, chars_format::scientific, "1.729e+37"},
+    {1.729e38f, chars_format::scientific, "1.729e+38"},
+
+    // Test all of the cases for fixed notation, including the non-Ryu fallback for large integers.
+    {1.729e-4f, chars_format::fixed, "0.0001729"},
+    {1.729e-3f, chars_format::fixed, "0.001729"},
+    {1.729e-2f, chars_format::fixed, "0.01729"},
+    {1.729e-1f, chars_format::fixed, "0.1729"},
+    {1.729e0f, chars_format::fixed, "1.729"},
+    {1.729e1f, chars_format::fixed, "17.29"},
+    {1.729e2f, chars_format::fixed, "172.9"},
+    {1.729e3f, chars_format::fixed, "1729"},
+    {1.729e4f, chars_format::fixed, "17290"},
+    {1.729e5f, chars_format::fixed, "172900"},
+    {1.729e6f, chars_format::fixed, "1729000"},
+    {1.729e7f, chars_format::fixed, "17290000"},
+    {1.729e8f, chars_format::fixed, "172900000"},
+    {1.729e9f, chars_format::fixed, "1728999936"},
+    {1.729e10f, chars_format::fixed, "17290000384"},
+    {1.729e11f, chars_format::fixed, "172900007936"},
+    {1.729e12f, chars_format::fixed, "1728999981056"},
+    {1.729e13f, chars_format::fixed, "17290000072704"},
+    {1.729e14f, chars_format::fixed, "172899998629888"},
+    {1.729e15f, chars_format::fixed, "1729000019853312"},
+    {1.729e16f, chars_format::fixed, "17289999661662208"},
+    {1.729e17f, chars_format::fixed, "172900007354040320"},
+    {1.729e18f, chars_format::fixed, "1729000039180664832"},
+    {1.729e19f, chars_format::fixed, "17289999567172927488"},
+    {1.729e20f, chars_format::fixed, "172899997870752530432"},
+    {1.729e21f, chars_format::fixed, "1729000013891897393152"},
+    {1.729e22f, chars_format::fixed, "17290000138918973931520"},
+    {1.729e23f, chars_format::fixed, "172899999137389925629952"},
+    {1.729e24f, chars_format::fixed, "1729000063431493294227456"},
+    {1.729e25f, chars_format::fixed, "17289999481393428335427584"},
+    {1.729e26f, chars_format::fixed, "172900004037306320209051648"},
+    {1.729e27f, chars_format::fixed, "1729000040373063202090516480"},
+    {1.729e28f, chars_format::fixed, "17290000403730632020905164800"},
+    {1.729e29f, chars_format::fixed, "172900004037306320209051648000"},
+    {1.729e30f, chars_format::fixed, "1728999964815199476176193060864"},
+    {1.729e31f, chars_format::fixed, "17290000252614904569076517961728"},
+    {1.729e32f, chars_format::fixed, "172899990436890849544473432555520"},
+    {1.729e33f, chars_format::fixed, "1729000059111413406117268687945728"},
+    {1.729e34f, chars_format::fixed, "17290000281629124239827618154676224"},
+    {1.729e35f, chars_format::fixed, "172899995388651006685994532152016896"},
+    {1.729e36f, chars_format::fixed, "1728999993500591323992114118292144128"},
+    {1.729e37f, chars_format::fixed, "17289999935005913239921141182921441280"},
+    {1.729e38f, chars_format::fixed, "172899996814757931942752608835808002048"},
+
+    // Also test one-digit cases, where the decimal point can't appear between digits like "17.29".
+    {7e-3f, chars_format::fixed, "0.007"},
+    {7e-2f, chars_format::fixed, "0.07"},
+    {7e-1f, chars_format::fixed, "0.7"},
+    {7e0f, chars_format::fixed, "7"},
+    {7e1f, chars_format::fixed, "70"},
+    {7e2f, chars_format::fixed, "700"},
+    {7e3f, chars_format::fixed, "7000"},
+
+    // Test the maximum value in fixed notation.
+    {0x1.fffffep+127f, chars_format::fixed, "340282346638528859811704183484516925440"},
+
+    // Test highly-trimmed powers of 2.
+    {0x1p118f, chars_format::fixed, "332306998946228968225951765070086144"},
+    {0x1p118f, chars_format::scientific, "3.32307e+35"},
+    {0x1p119f, chars_format::fixed, "664613997892457936451903530140172288"},
+    {0x1p119f, chars_format::scientific, "6.64614e+35"},
+
+    // Test powers of 10 that are exactly representable.
+    {1e0f, chars_format::fixed, "1"},
+    {1e1f, chars_format::fixed, "10"},
+    {1e2f, chars_format::fixed, "100"},
+    {1e3f, chars_format::fixed, "1000"},
+    {1e4f, chars_format::fixed, "10000"},
+    {1e5f, chars_format::fixed, "100000"},
+    {1e6f, chars_format::fixed, "1000000"},
+    {1e7f, chars_format::fixed, "10000000"},
+    {1e8f, chars_format::fixed, "100000000"},
+    {1e9f, chars_format::fixed, "1000000000"},
+    {1e10f, chars_format::fixed, "10000000000"},
+
+    // Test powers of 10 that aren't exactly representable.
+    // This exercises the "adjustment" code.
+    {1e11f, chars_format::fixed, "99999997952"},
+    {1e12f, chars_format::fixed, "999999995904"},
+    {1e13f, chars_format::fixed, "9999999827968"},
+    {1e14f, chars_format::fixed, "100000000376832"},
+    {1e15f, chars_format::fixed, "999999986991104"},
+    {1e16f, chars_format::fixed, "10000000272564224"},
+    {1e17f, chars_format::fixed, "99999998430674944"},
+    {1e18f, chars_format::fixed, "999999984306749440"},
+    {1e19f, chars_format::fixed, "9999999980506447872"},
+    {1e20f, chars_format::fixed, "100000002004087734272"},
+    {1e21f, chars_format::fixed, "1000000020040877342720"},
+    {1e22f, chars_format::fixed, "9999999778196308361216"},
+    {1e23f, chars_format::fixed, "99999997781963083612160"},
+    {1e24f, chars_format::fixed, "1000000013848427855085568"},
+    {1e25f, chars_format::fixed, "9999999562023526247432192"},
+    {1e26f, chars_format::fixed, "100000002537764290115403776"},
+    {1e27f, chars_format::fixed, "999999988484154753734934528"},
+    {1e28f, chars_format::fixed, "9999999442119689768320106496"},
+    {1e29f, chars_format::fixed, "100000001504746621987668885504"},
+    {1e30f, chars_format::fixed, "1000000015047466219876688855040"},
+    {1e31f, chars_format::fixed, "9999999848243207295109594873856"},
+    {1e32f, chars_format::fixed, "100000003318135351409612647563264"},
+    {1e33f, chars_format::fixed, "999999994495727286427992885035008"},
+    {1e34f, chars_format::fixed, "9999999790214767953607394487959552"},
+    {1e35f, chars_format::fixed, "100000004091847875962975319375216640"},
+    {1e36f, chars_format::fixed, "999999961690316245365415600208216064"},
+    {1e37f, chars_format::fixed, "9999999933815812510711506376257961984"},
+    {1e38f, chars_format::fixed, "99999996802856924650656260769173209088"},
+
+    // These numbers have odd mantissas (unaffected by shifting)
+    // that are barely within the "max shifted mantissa" limit.
+    // They're exactly-representable multiples of powers of 10, and can use Ryu with zero-filling.
+    {3355443e1f, chars_format::fixed, "33554430"},
+    {671087e2f, chars_format::fixed, "67108700"},
+    {134217e3f, chars_format::fixed, "134217000"},
+    {26843e4f, chars_format::fixed, "268430000"},
+    {5367e5f, chars_format::fixed, "536700000"},
+    {1073e6f, chars_format::fixed, "1073000000"},
+    {213e7f, chars_format::fixed, "2130000000"},
+    {41e8f, chars_format::fixed, "4100000000"},
+    {7e9f, chars_format::fixed, "7000000000"},
+    {1e10f, chars_format::fixed, "10000000000"},
+
+    // These numbers have odd mantissas (unaffected by shifting)
+    // that are barely above the "max shifted mantissa" limit.
+    // This activates the non-Ryu fallback for large integers.
+    {3355445e1f, chars_format::fixed, "33554448"},
+    {671089e2f, chars_format::fixed, "67108896"},
+    {134219e3f, chars_format::fixed, "134219008"},
+    {26845e4f, chars_format::fixed, "268449984"},
+    {5369e5f, chars_format::fixed, "536899968"},
+    {1075e6f, chars_format::fixed, "1075000064"},
+    {215e7f, chars_format::fixed, "2150000128"},
+    {43e8f, chars_format::fixed, "4300000256"},
+    {9e9f, chars_format::fixed, "8999999488"},
+    {3e10f, chars_format::fixed, "30000001024"},
+
+    // Test the mantissa shifting logic.
+    {5495808e5f, chars_format::fixed, "549580800000"}, // 5367 * 2^10
+    {5497856e5f, chars_format::fixed, "549785567232"}, // 5369 * 2^10
+
+    // Inspect all of those numbers in scientific notation.
+    // For the within-limit numbers, this verifies that Ryu is actually being used with zero-filling above.
+    // For the above-limit numbers, this tests Ryu's trimming.
+    {3355443e1f, chars_format::scientific, "3.355443e+07"},
+    {671087e2f, chars_format::scientific, "6.71087e+07"},
+    {134217e3f, chars_format::scientific, "1.34217e+08"},
+    {26843e4f, chars_format::scientific, "2.6843e+08"},
+    {5367e5f, chars_format::scientific, "5.367e+08"},
+    {1073e6f, chars_format::scientific, "1.073e+09"},
+    {213e7f, chars_format::scientific, "2.13e+09"},
+    {41e8f, chars_format::scientific, "4.1e+09"},
+    {7e9f, chars_format::scientific, "7e+09"},
+    {1e10f, chars_format::scientific, "1e+10"},
+    {3355445e1f, chars_format::scientific, "3.355445e+07"},
+    {671089e2f, chars_format::scientific, "6.71089e+07"},
+    {134219e3f, chars_format::scientific, "1.34219e+08"},
+    {26845e4f, chars_format::scientific, "2.6845e+08"},
+    {5369e5f, chars_format::scientific, "5.369e+08"},
+    {1075e6f, chars_format::scientific, "1.075e+09"},
+    {215e7f, chars_format::scientific, "2.15e+09"},
+    {43e8f, chars_format::scientific, "4.3e+09"},
+    {9e9f, chars_format::scientific, "9e+09"},
+    {3e10f, chars_format::scientific, "3e+10"},
+    {5495808e5f, chars_format::scientific, "5.495808e+11"},
+    {5497856e5f, chars_format::scientific, "5.497856e+11"},
+
+    // Test the switching logic of chars_format::general.
+    // C11 7.21.6.1 "The fprintf function"/8:
+    // "Let P equal [...] 6 if the precision is omitted [...].
+    // Then, if a conversion with style E would have an exponent of X:
+    // - if P > X >= -4, the conversion is with style f [...].
+    // - otherwise, the conversion is with style e [...]."
+    {1e-6f, chars_format::general, "1e-06"},
+    {1e-5f, chars_format::general, "1e-05"},
+    {1e-4f, chars_format::general, "0.0001"},
+    {1e-3f, chars_format::general, "0.001"},
+    {1e-2f, chars_format::general, "0.01"},
+    {1e-1f, chars_format::general, "0.1"},
+    {1e0f, chars_format::general, "1"},
+    {1e1f, chars_format::general, "10"},
+    {1e2f, chars_format::general, "100"},
+    {1e3f, chars_format::general, "1000"},
+    {1e4f, chars_format::general, "10000"},
+    {1e5f, chars_format::general, "100000"},
+    {1e6f, chars_format::general, "1e+06"},
+    {1e7f, chars_format::general, "1e+07"},
+    {1.234e-6f, chars_format::general, "1.234e-06"},
+    {1.234e-5f, chars_format::general, "1.234e-05"},
+    {1.234e-4f, chars_format::general, "0.0001234"},
+    {1.234e-3f, chars_format::general, "0.001234"},
+    {1.234e-2f, chars_format::general, "0.01234"},
+    {1.234e-1f, chars_format::general, "0.1234"},
+    {1.234e0f, chars_format::general, "1.234"},
+    {1.234e1f, chars_format::general, "12.34"},
+    {1.234e2f, chars_format::general, "123.4"},
+    {1.234e3f, chars_format::general, "1234"},
+    {1.234e4f, chars_format::general, "12340"},
+    {1.234e5f, chars_format::general, "123400"},
+    {1.234e6f, chars_format::general, "1.234e+06"},
+    {1.234e7f, chars_format::general, "1.234e+07"},
+    {1.234e8f, chars_format::general, "1.234e+08"},
+    {1.234e9f, chars_format::general, "1.234e+09"},
+    {1.234e10f, chars_format::general, "1.234e+10"},
+
+    // Test the switching logic of the plain overload.
+    // N4762 19.19.2 [charconv.to.chars]/8:
+    // "The conversion specifier is f or e, chosen according to the requirement
+    // for a shortest representation (see above); a tie is resolved in favor of f."
+    {1e-6f, chars_format{}, "1e-06"},
+    {1e-5f, chars_format{}, "1e-05"},
+    {1e-4f, chars_format{}, "1e-04"},
+    {1e-3f, chars_format{}, "0.001"},
+    {1e-2f, chars_format{}, "0.01"},
+    {1e-1f, chars_format{}, "0.1"},
+    {1e0f, chars_format{}, "1"},
+    {1e1f, chars_format{}, "10"},
+    {1e2f, chars_format{}, "100"},
+    {1e3f, chars_format{}, "1000"},
+    {1e4f, chars_format{}, "10000"},
+    {1e5f, chars_format{}, "1e+05"},
+    {1e6f, chars_format{}, "1e+06"},
+    {1e7f, chars_format{}, "1e+07"},
+    {1.234e-6f, chars_format{}, "1.234e-06"},
+    {1.234e-5f, chars_format{}, "1.234e-05"},
+    {1.234e-4f, chars_format{}, "0.0001234"},
+    {1.234e-3f, chars_format{}, "0.001234"},
+    {1.234e-2f, chars_format{}, "0.01234"},
+    {1.234e-1f, chars_format{}, "0.1234"},
+    {1.234e0f, chars_format{}, "1.234"},
+    {1.234e1f, chars_format{}, "12.34"},
+    {1.234e2f, chars_format{}, "123.4"},
+    {1.234e3f, chars_format{}, "1234"},
+    {1.234e4f, chars_format{}, "12340"},
+    {1.234e5f, chars_format{}, "123400"},
+    {1.234e6f, chars_format{}, "1234000"},
+    {1.234e7f, chars_format{}, "12340000"},
+    {1.234e8f, chars_format{}, "123400000"},
+    {1.234e9f, chars_format{}, "1.234e+09"},
+    {1.234e10f, chars_format{}, "1.234e+10"},
+
+    // Test hexfloat corner cases.
+    {0x1.728p+0f, chars_format::hex, "1.728p+0"}, // instead of "2.e5p-1"
+    {0x0.000002p-126f, chars_format::hex, "0.000002p-126"}, // instead of "1p-149", min subnormal
+    {0x0.fffffep-126f, chars_format::hex, "0.fffffep-126"}, // max subnormal
+    {0x1p-126f, chars_format::hex, "1p-126"}, // min normal
+    {0x1.fffffep+127f, chars_format::hex, "1.fffffep+127"}, // max normal
+
+    // Test hexfloat exponents.
+    {0x1p-109f, chars_format::hex, "1p-109"},
+    {0x1p-99f, chars_format::hex, "1p-99"},
+    {0x1p-9f, chars_format::hex, "1p-9"},
+    {0x1p+0f, chars_format::hex, "1p+0"},
+    {0x1p+9f, chars_format::hex, "1p+9"},
+    {0x1p+99f, chars_format::hex, "1p+99"},
+    {0x1p+109f, chars_format::hex, "1p+109"},
+
+    // Test hexfloat hexits.
+    {0x1.0123p+0f, chars_format::hex, "1.0123p+0"},
+    {0x1.4567p+0f, chars_format::hex, "1.4567p+0"},
+    {0x1.89abp+0f, chars_format::hex, "1.89abp+0"},
+    {0x1.cdefp+0f, chars_format::hex, "1.cdefp+0"},
+
+    // Test hexfloat trimming.
+    {0x1.00000ap+0f, chars_format::hex, "1.00000ap+0"},
+    {0x1.0000ap+0f, chars_format::hex, "1.0000ap+0"},
+    {0x1.000ap+0f, chars_format::hex, "1.000ap+0"},
+    {0x1.00ap+0f, chars_format::hex, "1.00ap+0"},
+    {0x1.0ap+0f, chars_format::hex, "1.0ap+0"},
+    {0x1.ap+0f, chars_format::hex, "1.ap+0"},
+    {0x1p+0f, chars_format::hex, "1p+0"},
+
+    // https://www.exploringbinary.com/the-shortest-decimal-string-that-round-trips-may-not-be-the-nearest/
+    // This is an exhaustive list of anomalous values.
+    // (See double_to_chars_test_cases.hpp for more details.)
+    {0x1p90f, chars_format::scientific, "1.2379401e+27"},
+    {0x1p87f, chars_format::scientific, "1.5474251e+26"},
+    {0x1p-96f, chars_format::scientific, "1.2621775e-29"},
+};
+
+#endif // FLOAT_TO_CHARS_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/floating_point_test_cases.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef FLOATING_POINT_TEST_CASES_HPP
+#define FLOATING_POINT_TEST_CASES_HPP
+
+#include <stdint.h>
+#include <utility>
+
+constexpr std::pair<const char*, uint64_t> floating_point_test_cases_double[] = {
+    // Verify small exactly-representable integers:
+    {"1", 0x3FF0000000000000ULL},
+    {"2", 0x4000000000000000ULL},
+    {"3", 0x4008000000000000ULL},
+    {"4", 0x4010000000000000ULL},
+    {"5", 0x4014000000000000ULL},
+    {"6", 0x4018000000000000ULL},
+    {"7", 0x401C000000000000ULL},
+    {"8", 0x4020000000000000ULL},
+
+    // Verify large exactly-representable integers:
+    {"9007199254740984", 0x433FFFFFFFFFFFF8ULL},
+    {"9007199254740985", 0x433FFFFFFFFFFFF9ULL},
+    {"9007199254740986", 0x433FFFFFFFFFFFFAULL},
+    {"9007199254740987", 0x433FFFFFFFFFFFFBULL},
+    {"9007199254740988", 0x433FFFFFFFFFFFFCULL},
+    {"9007199254740989", 0x433FFFFFFFFFFFFDULL},
+    {"9007199254740990", 0x433FFFFFFFFFFFFEULL},
+    {"9007199254740991", 0x433FFFFFFFFFFFFFULL}, // 2^53 - 1
+
+    // Verify the smallest denormal values:
+    {"5.0e-324", 0x0000000000000001ULL},
+    {"1.0e-323", 0x0000000000000002ULL},
+    {"1.5e-323", 0x0000000000000003ULL},
+    {"2.0e-323", 0x0000000000000004ULL},
+    {"2.5e-323", 0x0000000000000005ULL},
+    {"3.0e-323", 0x0000000000000006ULL},
+    {"3.5e-323", 0x0000000000000007ULL},
+    {"4.0e-323", 0x0000000000000008ULL},
+    {"4.5e-323", 0x0000000000000009ULL},
+    {"5.0e-323", 0x000000000000000AULL},
+    {"5.5e-323", 0x000000000000000BULL},
+    {"6.0e-323", 0x000000000000000CULL},
+    {"6.5e-323", 0x000000000000000DULL},
+    {"7.0e-323", 0x000000000000000EULL},
+    {"7.5e-323", 0x000000000000000FULL},
+
+    // Verify the largest denormal values:
+    {"2.2250738585071935e-308", 0x000FFFFFFFFFFFF0ULL},
+    {"2.2250738585071940e-308", 0x000FFFFFFFFFFFF1ULL},
+    {"2.2250738585071945e-308", 0x000FFFFFFFFFFFF2ULL},
+    {"2.2250738585071950e-308", 0x000FFFFFFFFFFFF3ULL},
+    {"2.2250738585071955e-308", 0x000FFFFFFFFFFFF4ULL},
+    {"2.2250738585071960e-308", 0x000FFFFFFFFFFFF5ULL},
+    {"2.2250738585071964e-308", 0x000FFFFFFFFFFFF6ULL},
+    {"2.2250738585071970e-308", 0x000FFFFFFFFFFFF7ULL},
+    {"2.2250738585071974e-308", 0x000FFFFFFFFFFFF8ULL},
+    {"2.2250738585071980e-308", 0x000FFFFFFFFFFFF9ULL},
+    {"2.2250738585071984e-308", 0x000FFFFFFFFFFFFAULL},
+    {"2.2250738585071990e-308", 0x000FFFFFFFFFFFFBULL},
+    {"2.2250738585071994e-308", 0x000FFFFFFFFFFFFCULL},
+    {"2.2250738585072000e-308", 0x000FFFFFFFFFFFFDULL},
+    {"2.2250738585072004e-308", 0x000FFFFFFFFFFFFEULL},
+    {"2.2250738585072010e-308", 0x000FFFFFFFFFFFFFULL},
+
+    // DevDiv#576315 "I/O library incorrect rounds floating point numbers on input"
+    // DevDiv#616647 "Visual C++ 11: iostream bug: incorrect input streaming of the smallest normal double and some
+    // denormals"
+    // DevDiv#730414 "iostreams is still misparsing floating-point"
+    // DevDiv#938627 "parsing float values using std::istream gives results inconsistent with sscanf() and with C++
+    // compiler"
+    // DevDiv#961116 "floating point string conversion accuracy"
+    {"2.2250738585072014e-308", 0x0010000000000000ULL}, // DBL_MIN
+    {"1.7976931348623158e+308", 0x7FEFFFFFFFFFFFFFULL}, // DBL_MAX
+    {"4.26144921954407e-309", 0x00031076B2F00000ULL},
+    {"179.9999999999999855", 0x40667FFFFFFFFFFFULL},
+    {"4.1", 0x4010666666666666ULL},
+    {"0.2288884", 0x3FCD4C37103785A8ULL},
+    {"0.168", 0x3FC5810624DD2F1BULL},
+    {"1.68", 0x3FFAE147AE147AE1ULL},
+    {"16.80000001", 0x4030CCCCCCF7BFEBULL},
+
+    // Test cases from Rick Regan's article, "Incorrectly Rounded Conversions in Visual C++":
+    // https://www.exploringbinary.com/incorrectly-rounded-conversions-in-visual-c-plus-plus/
+
+    // Example 1:
+    {"9214843084008499", 0x43405E6CEC57761AULL},
+
+    // Example 2 (2^-1 + 2^-53 + 2^-54):
+    {"0.500000000000000166533453693773481063544750213623046875", 0x3FE0000000000002ULL},
+
+    // Example 3:
+    {"30078505129381147446200", 0x44997A3C7271B021ULL},
+
+    // Example 4:
+    {"1777820000000000000001", 0x4458180D5BAD2E3EULL},
+
+    // Example 5 (2^-1 + 2^-53 + 2^-54 + 2^-66):
+    {"0.500000000000000166547006220929549868969843373633921146392822265625", 0x3FE0000000000002ULL},
+
+    // Example 6 (2^-1 + 2^-53 + 2^-54 + 2^-65):
+    {"0.50000000000000016656055874808561867439493653364479541778564453125", 0x3FE0000000000002ULL},
+
+    // Example 7:
+    {"0.3932922657273", 0x3FD92BB352C4623AULL},
+
+    // The following test cases are taken from other articles on Rick Regan's
+    // Exploring Binary blog. These are conversions that other implementations
+    // were found to perform incorrectly.
+
+    // https://www.exploringbinary.com/incorrectly-rounded-subnormal-conversions-in-java/
+    // Example 1 (2^-1047 + 2^-1075, half-ulp above a power of two):
+    {"6.6312368714697582767853966302759672433990999473553031442499717587"
+     "362866301392654396180682007880487441059604205526018528897150063763"
+     "256665955396033303618005191075917832333584923372080578494993608994"
+     "251286407188566165030934449228547591599881603044399098682919739314"
+     "266256986631577498362522745234853124423586512070512924530832781161"
+     "439325697279187097860044978723221938561502254152119972830784963194"
+     "121246401117772161481107528151017752957198119743384519360959074196"
+     "224175384736794951486324803914359317679811223967034438033355297560"
+     "033532098300718322306892013830155987921841729099279241763393155074"
+     "022348361207309147831684007154624400538175927027662135590421159867"
+     "638194826541287705957668068727833491469671712939495988506756821156"
+     "96218943412532098591327667236328125E-316",
+        0x0000000008000000ULL},
+
+    // Example 2 (2^-1058 - 2^-1075, half-ulp below a power of two):
+    {"3.2378839133029012895883524125015321748630376694231080599012970495"
+     "523019706706765657868357425877995578606157765598382834355143910841"
+     "531692526891905643964595773946180389283653051434639551003566966656"
+     "292020173313440317300443693602052583458034314716600326995807313009"
+     "548483639755486900107515300188817581841745696521731104736960227499"
+     "346384253806233697747365600089974040609674980283891918789639685754"
+     "392222064169814626901133425240027243859416510512935526014211553334"
+     "302252372915238433223313261384314778235911424088000307751706259156"
+     "707286570031519536642607698224949379518458015308952384398197084033"
+     "899378732414634842056080000272705311068273879077914449185347715987"
+     "501628125488627684932015189916680282517302999531439241685457086639"
+     "13273994694463908672332763671875E-319",
+        0x0000000000010000ULL},
+
+    // Example 3 (2^-1027 + 2^-1066 + 2^-1075, half-ulp above a non-power of two):
+    {"6.9533558078476771059728052155218916902221198171459507544162056079"
+     "800301315496366888061157263994418800653863998640286912755395394146"
+     "528315847956685600829998895513577849614468960421131982842131079351"
+     "102171626549398024160346762138294097205837595404767869364138165416"
+     "212878432484332023692099166122496760055730227032447997146221165421"
+     "888377703760223711720795591258533828013962195524188394697705149041"
+     "926576270603193728475623010741404426602378441141744972109554498963"
+     "891803958271916028866544881824524095839813894427833770015054620157"
+     "450178487545746683421617594966617660200287528887833870748507731929"
+     "971029979366198762266880963149896457660004790090837317365857503352"
+     "620998601508967187744019647968271662832256419920407478943826987518"
+     "09812609536720628966577351093292236328125E-310",
+        0x0000800000000100ULL},
+
+    // Example 4 (2^-1058 + 2^-1063 - 2^-1075, half-ulp below a non-power of two):
+    {"3.3390685575711885818357137012809439119234019169985217716556569973"
+     "284403145596153181688491490746626090999981130094655664268081703784"
+     "340657229916596426194677060348844249897410807907667784563321682004"
+     "646515939958173717821250106683466529959122339932545844611258684816"
+     "333436749050742710644097630907080178565840197768788124253120088123"
+     "262603630354748115322368533599053346255754042160606228586332807443"
+     "018924703005556787346899784768703698535494132771566221702458461669"
+     "916553215355296238706468887866375289955928004361779017462862722733"
+     "744717014529914330472578638646014242520247915673681950560773208853"
+     "293843223323915646452641434007986196650406080775491621739636492640"
+     "497383622906068758834568265867109610417379088720358034812416003767"
+     "05491726170293986797332763671875E-319",
+        0x0000000000010800ULL},
+
+    // A number between 2^-1074 and 2^-1075, just slightly larger than 2^-1075.
+    // It has bit 1075 set (the denormal rounding bit), followed by 2506 zeroes,
+    // followed by one bits. It should round up to 2^-1074.
+    {"2.470328229206232720882843964341106861825299013071623822127928412503"
+     "37753635104375932649918180817996189898282347722858865463328355177969"
+     "89819938739800539093906315035659515570226392290858392449105184435931"
+     "80284993653615250031937045767824921936562366986365848075700158576926"
+     "99037063119282795585513329278343384093519780155312465972635795746227"
+     "66465272827220056374006485499977096599470454020828166226237857393450"
+     "73633900796776193057750674017632467360096895134053553745851666113422"
+     "37666786041621596804619144672918403005300575308490487653917113865916"
+     "46239524912623653881879636239373280423891018672348497668235089863388"
+     "58792562830275599565752445550725518931369083625477918694866799496832"
+     "40497058210285131854513962138377228261454376934125320985913276672363"
+     "28125001e-324",
+        0x0000000000000001ULL},
+
+    // This value has a non-terminating binary fraction. It has a 0 at bit 54 followed by 120 ones.
+    {"1.8254370818746402660437411213933955878019332885742187", 0x3FFD34FD8378EA83ULL},
+
+    // https://www.exploringbinary.com/incorrect-decimal-to-floating-point-conversion-in-sqlite/
+    {"1e-23", 0x3B282DB34012B251ULL},
+    {"8.533e+68", 0x4E3FA69165A8EEA2ULL},
+    {"4.1006e-184", 0x19DBE0D1C7EA60C9ULL},
+    {"9.998e+307", 0x7FE1CC0A350CA87BULL},
+    {"9.9538452227e-280", 0x0602117AE45CDE43ULL},
+    {"6.47660115e-260", 0x0A1FDD9E333BADADULL},
+    {"7.4e+47", 0x49E033D7ECA0ADEFULL},
+    {"5.92e+48", 0x4A1033D7ECA0ADEFULL},
+    {"7.35e+66", 0x4DD172B70EABABA9ULL},
+    {"8.32116e+55", 0x4B8B2628393E02CDULL},
+};
+
+constexpr std::pair<const char*, uint32_t> floating_point_test_cases_float[] = {
+    // Verify small exactly-representable integers:
+    {"1", 0x3F800000U},
+    {"2", 0x40000000U},
+    {"3", 0x40400000U},
+    {"4", 0x40800000U},
+    {"5", 0x40A00000U},
+    {"6", 0x40C00000U},
+    {"7", 0x40E00000U},
+    {"8", 0x41000000U},
+
+    // Verify large exactly-representable integers:
+    {"16777208", 0x4B7FFFF8U},
+    {"16777209", 0x4B7FFFF9U},
+    {"16777210", 0x4B7FFFFAU},
+    {"16777211", 0x4B7FFFFBU},
+    {"16777212", 0x4B7FFFFCU},
+    {"16777213", 0x4B7FFFFDU},
+    {"16777214", 0x4B7FFFFEU},
+    {"16777215", 0x4B7FFFFFU}, // 2^24 - 1
+
+    // Verify the smallest denormal values:
+    {"1.4012984643248170e-45", 0x00000001U},
+    {"2.8025969286496340e-45", 0x00000002U},
+    {"4.2038953929744510e-45", 0x00000003U},
+    {"5.6051938572992680e-45", 0x00000004U},
+    {"7.0064923216240850e-45", 0x00000005U},
+    {"8.4077907859489020e-45", 0x00000006U},
+    {"9.8090892502737200e-45", 0x00000007U},
+    {"1.1210387714598537e-44", 0x00000008U},
+    {"1.2611686178923354e-44", 0x00000009U},
+    {"1.4012984643248170e-44", 0x0000000AU},
+    {"1.5414283107572988e-44", 0x0000000BU},
+    {"1.6815581571897805e-44", 0x0000000CU},
+    {"1.8216880036222622e-44", 0x0000000DU},
+    {"1.9618178500547440e-44", 0x0000000EU},
+    {"2.1019476964872256e-44", 0x0000000FU},
+
+    // Verify the largest denormal values:
+    {"1.1754921087447446e-38", 0x007FFFF0U},
+    {"1.1754922488745910e-38", 0x007FFFF1U},
+    {"1.1754923890044375e-38", 0x007FFFF2U},
+    {"1.1754925291342839e-38", 0x007FFFF3U},
+    {"1.1754926692641303e-38", 0x007FFFF4U},
+    {"1.1754928093939768e-38", 0x007FFFF5U},
+    {"1.1754929495238232e-38", 0x007FFFF6U},
+    {"1.1754930896536696e-38", 0x007FFFF7U},
+    {"1.1754932297835160e-38", 0x007FFFF8U},
+    {"1.1754933699133625e-38", 0x007FFFF9U},
+    {"1.1754935100432089e-38", 0x007FFFFAU},
+    {"1.1754936501730553e-38", 0x007FFFFBU},
+    {"1.1754937903029018e-38", 0x007FFFFCU},
+    {"1.1754939304327482e-38", 0x007FFFFDU},
+    {"1.1754940705625946e-38", 0x007FFFFEU},
+    {"1.1754942106924411e-38", 0x007FFFFFU},
+
+    // DevDiv#576315 "I/O library incorrect rounds floating point numbers on input"
+    // DevDiv#616647 "Visual C++ 11: iostream bug: incorrect input streaming of the smallest normal double and some
+    // denormals"
+    // DevDiv#730414 "iostreams is still misparsing floating-point"
+    // DevDiv#938627 "parsing float values using std::istream gives results inconsistent with sscanf() and with C++
+    // compiler"
+    // DevDiv#961116 "floating point string conversion accuracy"
+    {"1.175494351e-38", 0x00800000U}, // FLT_MIN
+    {"3.402823466e+38", 0x7F7FFFFFU}, // FLT_MAX
+    {"179.9999999999999855", 0x43340000U},
+    {"4.1", 0x40833333U},
+    {"0.2288884", 0x3E6A61B9U},
+    {"0.168", 0x3E2C0831U},
+    {"1.68", 0x3FD70A3DU},
+    {"16.80000001", 0x41866666U},
+};
+
+#endif // FLOATING_POINT_TEST_CASES_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/test.hpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#ifndef TEST_HPP
+#define TEST_HPP
+
+#include <charconv>
+#include <limits>
+#include <stddef.h>
+#include <system_error>
+using namespace std;
+
+inline constexpr float float_inf         = numeric_limits<float>::infinity();
+inline constexpr float float_nan         = numeric_limits<float>::quiet_NaN();
+inline constexpr float float_nan_payload = __builtin_nanf("1729");
+
+inline constexpr double double_inf         = numeric_limits<double>::infinity();
+inline constexpr double double_nan         = numeric_limits<double>::quiet_NaN();
+inline constexpr double double_nan_payload = __builtin_nan("1729");
+
+struct FloatFromCharsTestCase {
+    const char* input;
+    chars_format fmt;
+    size_t correct_idx;
+    errc correct_ec;
+    float correct_value;
+};
+
+struct FloatToCharsTestCase {
+    float value;
+    chars_format fmt;
+    const char* correct;
+};
+
+struct FloatPrecisionToCharsTestCase {
+    float value;
+    chars_format fmt;
+    int precision;
+    const char* correct;
+};
+
+struct DoubleFromCharsTestCase {
+    const char* input;
+    chars_format fmt;
+    size_t correct_idx;
+    errc correct_ec;
+    double correct_value;
+};
+
+struct DoubleToCharsTestCase {
+    double value;
+    chars_format fmt;
+    const char* correct;
+};
+
+struct DoublePrecisionToCharsTestCase {
+    double value;
+    chars_format fmt;
+    int precision;
+    const char* correct;
+};
+
+#endif // TEST_HPP

libcxx/test/std/utilities/charconv/charconv.msvc/test.cpp

+// Copyright (c) Microsoft Corporation.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+
+#include "test.hpp"
+
+#include <algorithm>
+#include <array>
+#include <assert.h>
+#include <charconv>
+#include <chrono>
+#include <cmath>
+#include <fstream>
+#include <functional>
+#include <limits>
+#include <locale>
+#include <optional>
+#include <random>
+#include <set>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <string>
+#include <string_view>
+#include <system_error>
+#include <type_traits>
+#include <utility>
+#include <vector>
+
+#include "double_fixed_precision_to_chars_test_cases_1.hpp"
+#include "double_fixed_precision_to_chars_test_cases_2.hpp"
+#include "double_fixed_precision_to_chars_test_cases_3.hpp"
+#include "double_fixed_precision_to_chars_test_cases_4.hpp"
+#include "double_from_chars_test_cases.hpp"
+#include "double_general_precision_to_chars_test_cases.hpp"
+#include "double_hex_precision_to_chars_test_cases.hpp"
+#include "double_scientific_precision_to_chars_test_cases_1.hpp"
+#include "double_scientific_precision_to_chars_test_cases_2.hpp"
+#include "double_scientific_precision_to_chars_test_cases_3.hpp"
+#include "double_scientific_precision_to_chars_test_cases_4.hpp"
+#include "double_to_chars_test_cases.hpp"
+#include "float_fixed_precision_to_chars_test_cases.hpp"
+#include "float_from_chars_test_cases.hpp"
+#include "float_general_precision_to_chars_test_cases.hpp"
+#include "float_hex_precision_to_chars_test_cases.hpp"
+#include "float_scientific_precision_to_chars_test_cases.hpp"
+#include "float_to_chars_test_cases.hpp"
+
+using namespace std;
+
+void initialize_randomness(mt19937_64& mt64, const int argc, char** const argv) {
+    constexpr size_t n = mt19937_64::state_size;
+    constexpr size_t w = mt19937_64::word_size;
+    static_assert(w % 32 == 0);
+    constexpr size_t k = w / 32;
+
+    vector<uint32_t> vec(n * k);
+
+    puts("USAGE:");
+    puts("test.exe              : generates seed data from random_device.");
+    puts("test.exe filename.txt : loads seed data from a given text file.");
+
+    if (argc == 1) {
+        random_device rd;
+        generate(vec.begin(), vec.end(), ref(rd));
+        puts("Generated seed data.");
+    } else if (argc == 2) {
+        const char* const filename = argv[1];
+
+        ifstream file(filename);
+
+        if (!file) {
+            printf("ERROR: Can't open %s.\n", filename);
+            abort();
+        }
+
+        for (auto& elem : vec) {
+            file >> elem;
+
+            if (!file) {
+                printf("ERROR: Can't read seed data from %s.\n", filename);
+                abort();
+            }
+        }
+
+        printf("Loaded seed data from %s.\n", filename);
+    } else {
+        puts("ERROR: Too many command-line arguments.");
+        abort();
+    }
+
+    puts("SEED DATA:");
+    for (const auto& elem : vec) {
+        printf("%u ", elem);
+    }
+    printf("\n");
+
+    seed_seq seq(vec.cbegin(), vec.cend());
+
+    mt64.seed(seq);
+
+    puts("Successfully seeded mt64. First three values:");
+    for (int i = 0; i < 3; ++i) {
+        // libc++ uses long for 64-bit values.
+        printf("0x%016llX\n", static_cast<unsigned long long>(mt64()));
+    }
+}
+
+static_assert((chars_format::scientific & chars_format::fixed) == chars_format{});
+static_assert((chars_format::scientific & chars_format::hex) == chars_format{});
+static_assert((chars_format::fixed & chars_format::hex) == chars_format{});
+static_assert(chars_format::general == (chars_format::fixed | chars_format::scientific));
+
+template <typename T, typename Optional>
+void test_common_to_chars(
+    const T value, const Optional opt_arg, const optional<int> opt_precision, const string_view correct) {
+
+    // Important: Test every effective buffer size from 0 through correct.size() and slightly beyond. For the sizes
+    // less than correct.size(), this verifies that the too-small buffer is correctly detected, and that we don't
+    // attempt to write outside of it, even by a single char. (This exhaustive validation is necessary because the
+    // implementation must check whenever it attempts to write. Sometimes we can calculate the total size and perform
+    // a single check, but sometimes we need to check when writing each part of the result.) Testing correct.size()
+    // verifies that we can succeed without overrunning, and testing slightly larger sizes verifies that we can succeed
+    // without attempting to write to extra chars even when they're available. Finally, we also verify that we aren't
+    // underrunning the buffer. This is a concern because sometimes we walk backwards when rounding.
+
+    constexpr size_t BufferPrefix = 20; // detect buffer underruns (specific value isn't important)
+
+    constexpr size_t Space = is_integral_v<T> ? 1 + 64 // worst case: -2^63 in binary
+                           : is_same_v<T, float>
+                               ? 1 + 151 // worst case: negative min subnormal float, fixed notation
+                               : 1 + 1076; // worst case: negative min subnormal double, fixed notation
+
+    constexpr size_t BufferSuffix = 30; // detect buffer overruns (specific value isn't important)
+
+    array<char, BufferPrefix + Space + BufferSuffix> buff;
+
+    char* const buff_begin = buff.data();
+    char* const first      = buff_begin + BufferPrefix;
+    char* const buff_end   = buff_begin + buff.size();
+
+    constexpr size_t ExtraChars = 3;
+    static_assert(ExtraChars + 10 < BufferSuffix,
+        "The specific values aren't important, but there should be plenty of room to detect buffer overruns.");
+
+    for (size_t n = 0; n <= correct.size() + ExtraChars; ++n) {
+        assert(n <= static_cast<size_t>(buff_end - first));
+        char* const last = first + n;
+
+        buff.fill('@');
+        const auto is_fill_char = [](const char c) { return c == '@'; };
+
+        to_chars_result result{};
+        if (opt_precision.has_value()) {
+            assert(opt_arg.has_value());
+
+            if constexpr (is_floating_point_v<T>) {
+                result = to_chars(first, last, value, opt_arg.value(), opt_precision.value());
+            } else {
+                abort();
+            }
+        } else if (opt_arg.has_value()) {
+            result = to_chars(first, last, value, opt_arg.value());
+        } else {
+            result = to_chars(first, last, value);
+        }
+
+        if (n < correct.size()) {
+            assert(result.ptr == last);
+            assert(result.ec == errc::value_too_large);
+            assert(all_of(buff_begin, first, is_fill_char));
+            // [first, last) is unspecified
+            assert(all_of(last, buff_end, is_fill_char));
+        } else {
+            assert(result.ptr == first + correct.size());
+            assert(result.ec == errc{});
+            assert(all_of(buff_begin, first, is_fill_char));
+            assert(equal(first, result.ptr, correct.begin(), correct.end()));
+            assert(all_of(result.ptr, buff_end, is_fill_char));
+        }
+    }
+}
+
+template <typename T>
+void test_integer_to_chars(const T value, const optional<int> opt_base, const string_view correct) {
+
+    test_common_to_chars(value, opt_base, nullopt, correct);
+
+    { // Also test successful from_chars() scenarios.
+        const char* const correct_first = correct.data();
+        const char* const correct_last  = correct_first + correct.size();
+
+        T dest = 0;
+
+        const from_chars_result from_res =
+            (opt_base.has_value() ? from_chars(correct_first, correct_last, dest, opt_base.value())
+                                  : from_chars(correct_first, correct_last, dest));
+
+        assert(from_res.ptr == correct_last);
+        assert(from_res.ec == errc{});
+        assert(dest == value);
+    }
+}
+
+// https://www.wolframalpha.com : Table[BaseForm[n * 2 - 1, n], {n, 2, 36}]
+constexpr const char* output_max_digit[] = {"skip0", "skip1", "11", "12", "13", "14", "15", "16", "17", "18", "19",
+    "1a", "1b", "1c", "1d", "1e", "1f", "1g", "1h", "1i", "1j", "1k", "1l", "1m", "1n", "1o", "1p", "1q", "1r", "1s",
+    "1t", "1u", "1v", "1w", "1x", "1y", "1z"};
+
+// https://www.wolframalpha.com : Table[BaseForm[k, n], {k, {MEOW, MEOW, MEOW}}, {n, 2, 36}]
+constexpr uint64_t stress_chunks_positive                          = 12000000345000678900ULL;
+constexpr pair<uint64_t, array<const char*, 37>> output_positive[] = {
+    {123U, {{"skip0", "skip1", "1111011", "11120", "1323", "443", "323", "234", "173", "146", "123", "102", "a3", "96",
+               "8b", "83", "7b", "74", "6f", "69", "63", "5i", "5d", "58", "53", "4n", "4j", "4f", "4b", "47", "43",
+               "3u", "3r", "3o", "3l", "3i", "3f"}}},
+    {uint64_t{INT8_MAX}, {{"skip0", "skip1", "1111111", "11201", "1333", "1002", "331", "241", "177", "151", "127",
+                             "106", "a7", "9a", "91", "87", "7f", "78", "71", "6d", "67", "61", "5h", "5c", "57", "52",
+                             "4n", "4j", "4f", "4b", "47", "43", "3v", "3s", "3p", "3m", "3j"}}},
+    {161U, {{"skip0", "skip1", "10100001", "12222", "2201", "1121", "425", "320", "241", "188", "161", "137", "115",
+               "c5", "b7", "ab", "a1", "98", "8h", "89", "81", "7e", "77", "70", "6h", "6b", "65", "5q", "5l", "5g",
+               "5b", "56", "51", "4t", "4p", "4l", "4h"}}},
+    {UINT8_MAX, {{"skip0", "skip1", "11111111", "100110", "3333", "2010", "1103", "513", "377", "313", "255", "212",
+                    "193", "168", "143", "120", "ff", "f0", "e3", "d8", "cf", "c3", "bd", "b2", "af", "a5", "9l", "9c",
+                    "93", "8n", "8f", "87", "7v", "7o", "7h", "7a", "73"}}},
+    {1729U, {{"skip0", "skip1", "11011000001", "2101001", "123001", "23404", "12001", "5020", "3301", "2331", "1729",
+                "1332", "1001", "a30", "8b7", "7a4", "6c1", "5gc", "561", "4f0", "469", "3j7", "3cd", "364", "301",
+                "2j4", "2ed", "2a1", "25l", "21i", "1rj", "1oo", "1m1", "1jd", "1gt", "1ee", "1c1"}}},
+    {uint64_t{INT16_MAX}, {{"skip0", "skip1", "111111111111111", "1122221121", "13333333", "2022032", "411411",
+                              "164350", "77777", "48847", "32767", "22689", "16b67", "11bb7", "bd27", "9a97", "7fff",
+                              "6b68", "5b27", "4eeb", "41i7", "3b67", "31f9", "2flf", "28l7", "22ah", "1mc7", "1hpg",
+                              "1dm7", "19rq", "16c7", "1330", "vvv", "u2v", "sbp", "qq7", "pa7"}}},
+    {57494U, {{"skip0", "skip1", "1110000010010110", "2220212102", "32002112", "3314434", "1122102", "326423", "160226",
+                 "86772", "57494", "3a218", "29332", "20228", "16d4a", "1207e", "e096", "bbg0", "9f82", "8750", "73ee",
+                 "647h", "58h8", "4gfh", "43je", "3goj", "3718", "2onb", "2h9a", "2aag", "23qe", "1spk", "1o4m", "1jq8",
+                 "1fp0", "1bwo", "18d2"}}},
+    {UINT16_MAX, {{"skip0", "skip1", "1111111111111111", "10022220020", "33333333", "4044120", "1223223", "362031",
+                     "177777", "108806", "65535", "45268", "31b13", "23aa2", "19c51", "14640", "ffff", "d5d0", "b44f",
+                     "9aa4", "83gf", "71cf", "638j", "58k8", "4hif", "44la", "3iof", "38o6", "2rgf", "2jqo", "2cof",
+                     "2661", "1vvv", "1r5u", "1mnh", "1ihf", "1ekf"}}},
+    {71125478U, {{"skip0", "skip1", "100001111010100100111100110", "11221211112210222", "10033110213212",
+                    "121202003403", "11020244342", "1522361624", "417244746", "157745728", "71125478", "3716a696",
+                    "1b9a06b2", "11973ba8", "9636514", "639e338", "43d49e6", "2g19gfb", "21b9d18", "19dec94", "124addi",
+                    "h8f25b", "dhdfa6", "b13hg2", "8m91he", "7720j3", "5pgj58", "4pmelq", "43k17i", "3dg8ek", "2ro898",
+                    "2f0et8", "23qif6", "1qw5lh", "1j7l7s", "1cdvli", "16cgrq"}}},
+    {uint64_t{INT32_MAX},
+        {{"skip0", "skip1", "1111111111111111111111111111111", "12112122212110202101", "1333333333333333",
+            "13344223434042", "553032005531", "104134211161", "17777777777", "5478773671", "2147483647", "a02220281",
+            "4bb2308a7", "282ba4aaa", "1652ca931", "c87e66b7", "7fffffff", "53g7f548", "3928g3h1", "27c57h32",
+            "1db1f927", "140h2d91", "ikf5bf1", "ebelf95", "b5gge57", "8jmdnkm", "6oj8ion", "5ehncka", "4clm98f",
+            "3hk7987", "2sb6cs7", "2d09uc1", "1vvvvvv", "1lsqtl1", "1d8xqrp", "15v22um", "zik0zj"}}},
+    {3522553278ULL,
+        {{"skip0", "skip1", "11010001111101011110010110111110", "100002111022020200020", "3101331132112332",
+            "24203233201103", "1341312313010", "153202131426", "32175362676", "10074266606", "3522553278", "1548431462",
+            "823842766", "441a34c6a", "255b8d486", "1593b4753", "d1f5e5be", "89ffb3b6", "5da3e606", "3hgbfb5i",
+            "2f0fj33i", "1k1ac536", "191b46e2", "10i6fmk8", "ia967l6", "eahia63", "baca9ga", "92d86i6", "78iq4i6",
+            "5qlc1dc", "4osos2i", "3u1862s", "38vbpdu", "2o0a7ro", "29hx9e6", "1w2dnod", "1m98ji6"}}},
+    {UINT32_MAX,
+        {{"skip0", "skip1", "11111111111111111111111111111111", "102002022201221111210", "3333333333333333",
+            "32244002423140", "1550104015503", "211301422353", "37777777777", "12068657453", "4294967295", "1904440553",
+            "9ba461593", "535a79888", "2ca5b7463", "1a20dcd80", "ffffffff", "a7ffda90", "704he7g3", "4f5aff65",
+            "3723ai4f", "281d55i3", "1fj8b183", "1606k7ib", "mb994af", "hek2mgk", "dnchbnl", "b28jpdl", "8pfgih3",
+            "76beigf", "5qmcpqf", "4q0jto3", "3vvvvvv", "3aokq93", "2qhxjlh", "2br45qa", "1z141z3"}}},
+    {545890816626160ULL,
+        {{"skip0", "skip1", "1111100000111110000011100001101100000110111110000", "2122120211122121121021010202111",
+            "1330013300130031200313300", "1033022333343024014120", "5213002440142255104", "222661211220253465",
+            "17407603415406760", "2576748547233674", "545890816626160", "148a34aa4706535", "51285369b87494",
+            "1a57a38b045a95", "98b3383b9766c", "4319d1601875a", "1f07c1c360df0", "ffd471f34f13", "88g09ff9dh84",
+            "4d0d5e232c53", "2d63h403i580", "1bf5h8185hdj", "kc3g550fkcg", "d41id5k9984", "8ef5n0him4g", "5i2dijfe1la",
+            "3me22fm5fhi", "2hfmhgg73kd", "1ngpfabr53c", "18i7220bh11", "rm0lcjngpa", "kk1elesni1", "fgfge3c3fg",
+            "bp4q5l6bjg", "8xna46jp0k", "6wejomvji5", "5di2s1qhv4"}}},
+    {uint64_t{INT64_MAX},
+        {{"skip0", "skip1", "111111111111111111111111111111111111111111111111111111111111111",
+            "2021110011022210012102010021220101220221", "13333333333333333333333333333333",
+            "1104332401304422434310311212", "1540241003031030222122211", "22341010611245052052300",
+            "777777777777777777777", "67404283172107811827", "9223372036854775807", "1728002635214590697",
+            "41a792678515120367", "10b269549075433c37", "4340724c6c71dc7a7", "160e2ad3246366807", "7fffffffffffffff",
+            "33d3d8307b214008", "16agh595df825fa7", "ba643dci0ffeehh", "5cbfjia3fh26ja7", "2heiciiie82dh97",
+            "1adaibb21dckfa7", "i6k448cf4192c2", "acd772jnc9l0l7", "64ie1focnn5g77", "3igoecjbmca687", "27c48l5b37oaop",
+            "1bk39f3ah3dmq7", "q1se8f0m04isb", "hajppbc1fc207", "bm03i95hia437", "7vvvvvvvvvvvv", "5hg4ck9jd4u37",
+            "3tdtk1v8j6tpp", "2pijmikexrxp7", "1y2p0ij32e8e7"}}},
+    {stress_chunks_positive,
+        {{"skip0", "skip1", "1010011010001000100100001011110000101100010101001001010111110100",
+            "2221221122020020011022001202200200202200", "22122020210023300230111021113310",
+            "1301130403021123030133211100", "2311004450342244200504500", "30325064311430214266301",
+            "1232104413605425112764", "87848206138052620680", "12000000345000678900", "2181782a1686924456a",
+            "54aa47a9058877b130", "150593a5b002c87b16", "571cad2b93c7760a8", "1c60d2676d4e53e00", "a68890bc2c5495f4",
+            "43499224707a4f4g", "1e052gdga1d26f40", "f06dh4g564c8a91", "769df0d9ace4h50", "3ee7bcj1ajghi4f",
+            "1k9agc4gfl0l43a", "10id7dakdlcjd22", "dge08fe0l5hl7c", "8184326d31ib60", "4ljbglf3cpim76",
+            "2pph66481kiiki", "1niph2ao132e58", "14qgbgk3c3iffg", "mhc35an1bhb00", "f78o8ur705ln5", "ad24gngm595fk",
+            "76e1n5i5v0ivl", "50wu8jsnks82g", "3ja41smfvqb1f", "2j64t3qgq0ut0"}}},
+    {14454900944617508688ULL,
+        {{"skip0", "skip1", "1100100010011010000111111101001011100011011000101000111101010000",
+            "10120022020112011211121221212101012220210", "30202122013331023203120220331100",
+            "1432224030234034034040234223", "3014532424232535441404120", "34610451042001242144165",
+            "1442320775134330507520", "116266464747855335823", "14454900944617508688", "266642a9a9471339935",
+            "662251403263939640", "1895280092bc310481", "68cb9c8292557406c", "23023deab20002893", "c89a1fd2e3628f50",
+            "50e7147a7db8ef84", "22a34a05086f78ec", "i1dgef04357g7i1", "8g90b882jcj8be8", "49c1kk35i0k24ic",
+            "272a16i54ebkacg", "15fdih7l3m7k8md", "gbj7303eg9nge0", "9hckfdkj3kkdmd", "5lc7hifdkl4nne",
+            "3f86e4mgpna5ol", "266pj428na273c", "1bomgjbnlg4m3f", "r5tf1f7f009ji", "iarsig29iqhhm", "ch6gvqbhm53qg",
+            "8lwtvcdj6rlqr", "61w23lajggp44", "49p1f3dsqqcdx", "31tkqqkxypopc"}}},
+    {UINT64_MAX,
+        {{"skip0", "skip1", "1111111111111111111111111111111111111111111111111111111111111111",
+            "11112220022122120101211020120210210211220", "33333333333333333333333333333333",
+            "2214220303114400424121122430", "3520522010102100444244423", "45012021522523134134601",
+            "1777777777777777777777", "145808576354216723756", "18446744073709551615", "335500516a429071284",
+            "839365134a2a240713", "219505a9511a867b72", "8681049adb03db171", "2c1d56b648c6cd110", "ffffffffffffffff",
+            "67979g60f5428010", "2d3fgb0b9cg4bd2f", "141c8786h1ccaagg", "b53bjh07be4dj0f", "5e8g4ggg7g56dif",
+            "2l4lf104353j8kf", "1ddh88h2782i515", "l12ee5fn0ji1if", "c9c336o0mlb7ef", "7b7n2pcniokcgf",
+            "4eo8hfam6fllmo", "2nc6j26l66rhof", "1n3rsh11f098rn", "14l9lkmo30o40f", "nd075ib45k86f", "fvvvvvvvvvvvv",
+            "b1w8p7j5q9r6f", "7orp63sh4dphh", "5g24a25twkwff", "3w5e11264sgsf"}}},
+};
+
+// https://www.wolframalpha.com : Table[BaseForm[k, n], {k, {MEOW, MEOW, MEOW}}, {n, 2, 36}]
+constexpr int64_t stress_chunks_negative                          = -9000876000000054321LL;
+constexpr pair<int64_t, array<const char*, 37>> output_negative[] = {
+    {-85, {{"skip0", "skip1", "-1010101", "-10011", "-1111", "-320", "-221", "-151", "-125", "-104", "-85", "-78",
+              "-71", "-67", "-61", "-5a", "-55", "-50", "-4d", "-49", "-45", "-41", "-3j", "-3g", "-3d", "-3a", "-37",
+              "-34", "-31", "-2r", "-2p", "-2n", "-2l", "-2j", "-2h", "-2f", "-2d"}}},
+    {INT8_MIN, {{"skip0", "skip1", "-10000000", "-11202", "-2000", "-1003", "-332", "-242", "-200", "-152", "-128",
+                   "-107", "-a8", "-9b", "-92", "-88", "-80", "-79", "-72", "-6e", "-68", "-62", "-5i", "-5d", "-58",
+                   "-53", "-4o", "-4k", "-4g", "-4c", "-48", "-44", "-40", "-3t", "-3q", "-3n", "-3k"}}},
+    {-1591, {{"skip0", "skip1", "-11000110111", "-2011221", "-120313", "-22331", "-11211", "-4432", "-3067", "-2157",
+                "-1591", "-1217", "-b07", "-955", "-819", "-711", "-637", "-58a", "-4g7", "-47e", "-3jb", "-3cg",
+                "-367", "-304", "-2i7", "-2dg", "-295", "-24p", "-20n", "-1pp", "-1n1", "-1ka", "-1hn", "-1f7", "-1cr",
+                "-1ag", "-187"}}},
+    {INT16_MIN, {{"skip0", "skip1", "-1000000000000000", "-1122221122", "-20000000", "-2022033", "-411412", "-164351",
+                    "-100000", "-48848", "-32768", "-2268a", "-16b68", "-11bb8", "-bd28", "-9a98", "-8000", "-6b69",
+                    "-5b28", "-4eec", "-41i8", "-3b68", "-31fa", "-2flg", "-28l8", "-22ai", "-1mc8", "-1hph", "-1dm8",
+                    "-19rr", "-16c8", "-1331", "-1000", "-u2w", "-sbq", "-qq8", "-pa8"}}},
+    {-66748412,
+        {{"skip0", "skip1", "-11111110100111111111111100", "-11122121011121102", "-3332213333330", "-114041422122",
+            "-10342352232", "-1440231533", "-376477774", "-148534542", "-66748412", "-34750085", "-1a42b678",
+            "-10aa0803", "-8c1731a", "-5cd7492", "-3fa7ffc", "-2d03163", "-1h5f3b2", "-17i39c6", "-10h3b0c", "-g749jh",
+            "-ckkdkg", "-a8c0ak", "-894afk", "-6klmbc", "-5g1i6g", "-4hg4gb", "-3ogi7o", "-37anqb", "-2mc4r2",
+            "-2a8h7i", "-1vkvvs", "-1n9ca5", "-1fw8sk", "-19gshh", "-13qnek"}}},
+    {INT32_MIN, {{"skip0", "skip1", "-10000000000000000000000000000000", "-12112122212110202102", "-2000000000000000",
+                    "-13344223434043", "-553032005532", "-104134211162", "-20000000000", "-5478773672", "-2147483648",
+                    "-a02220282", "-4bb2308a8", "-282ba4aab", "-1652ca932", "-c87e66b8", "-80000000", "-53g7f549",
+                    "-3928g3h2", "-27c57h33", "-1db1f928", "-140h2d92", "-ikf5bf2", "-ebelf96", "-b5gge58", "-8jmdnkn",
+                    "-6oj8ioo", "-5ehnckb", "-4clm98g", "-3hk7988", "-2sb6cs8", "-2d09uc2", "-2000000", "-1lsqtl2",
+                    "-1d8xqrq", "-15v22un", "-zik0zk"}}},
+    {-297139747082649553LL,
+        {{"skip0", "skip1", "-10000011111101001110000011010010001100000101011111111010001",
+            "-1222110012002112101210012211022102101", "-100133221300122101200223333101", "-4443033200104011124241203",
+            "-21313431255203203120401", "-350320603201030412545", "-20375160322140537721", "-1873162471705738371",
+            "-297139747082649553", "-65150976074a24025", "-173522497b5373101", "-5a60a99bc3b71654", "-1ca51a06cc38ba25",
+            "-a2a25babe62241d", "-41fa7069182bfd1", "-1d00134fba1769g", "-e4f799fc5f7e81", "-714ebbh8388188",
+            "-3cahb17836b3hd", "-1j8659jf5hbg3j", "-112bbb2jege5c5", "-dcjfmk2kjb4cc", "-836bm4klbgl61",
+            "-4ofia1416ee73", "-32ommgjef1l2h", "-1qc52eal5m8ba", "-17n53r05a4r15", "-oa88m2qiqjik", "-gn67qoat5r8d",
+            "-blgd6n5s90al", "-87t70q8o5fuh", "-5t09hwaqu9qg", "-47vssihaoa4x", "-32p24fbjye7x", "-299r8zck3841"}}},
+    {stress_chunks_negative,
+        {{"skip0", "skip1", "-111110011101001100010010000100010000111010101111001010000110001",
+            "-2012222010200021010000112111002001111200", "-13303221202100202013111321100301",
+            "-1101001100304341000003214241", "-1522150121302454031001413", "-22054250360123016161454",
+            "-763514220420725712061", "-65863607100474061450", "-9000876000000054321", "-1689813530958833498",
+            "-408258185a67069269", "-106b01597a47ba2948", "-41c02922bc776d49b", "-1584cd10979dc84b6",
+            "-7ce9890887579431", "-327cf6cbc67023c3", "-1604b5f6a0de8129", "-b50d3ef02f124a4", "-59h9bfif0006fg1",
+            "-2g5d8ekh05d2dfi", "-19i418c38g1chfj", "-hjgf7d0k0gla9a", "-a6b21ncehfa3f9", "-61060fnl003bml",
+            "-3g88bakondgf8l", "-25q3i730ed21di", "-1al84glo518iip", "-pcli8ig7pjhbo", "-gs31q8id2jnkl",
+            "-bd7kaglgdrbgk", "-7pqc9123lf51h", "-5d2sd1r5ms7su", "-3q833s8kdrun3", "-2n7vmqigfueqb",
+            "-1wdu892toj0a9"}}},
+    {INT64_MIN, {{"skip0", "skip1", "-1000000000000000000000000000000000000000000000000000000000000000",
+                    "-2021110011022210012102010021220101220222", "-20000000000000000000000000000000",
+                    "-1104332401304422434310311213", "-1540241003031030222122212", "-22341010611245052052301",
+                    "-1000000000000000000000", "-67404283172107811828", "-9223372036854775808", "-1728002635214590698",
+                    "-41a792678515120368", "-10b269549075433c38", "-4340724c6c71dc7a8", "-160e2ad3246366808",
+                    "-8000000000000000", "-33d3d8307b214009", "-16agh595df825fa8", "-ba643dci0ffeehi",
+                    "-5cbfjia3fh26ja8", "-2heiciiie82dh98", "-1adaibb21dckfa8", "-i6k448cf4192c3", "-acd772jnc9l0l8",
+                    "-64ie1focnn5g78", "-3igoecjbmca688", "-27c48l5b37oaoq", "-1bk39f3ah3dmq8", "-q1se8f0m04isc",
+                    "-hajppbc1fc208", "-bm03i95hia438", "-8000000000000", "-5hg4ck9jd4u38", "-3tdtk1v8j6tpq",
+                    "-2pijmikexrxp8", "-1y2p0ij32e8e8"}}},
+};
+
+template <typename T>
+void test_integer_to_chars() {
+    for (int base = 2; base <= 36; ++base) {
+        test_integer_to_chars(static_cast<T>(0), base, "0");
+        test_integer_to_chars(static_cast<T>(1), base, "1");
+
+        // tests [3, 71]
+        test_integer_to_chars(static_cast<T>(base * 2 - 1), base, output_max_digit[base]);
+
+        for (const auto& p : output_positive) {
+            if (p.first <= static_cast<uint64_t>(numeric_limits<T>::max())) {
+                test_integer_to_chars(static_cast<T>(p.first), base, p.second[static_cast<size_t>(base)]);
+            }
+        }
+
+        if constexpr (is_signed_v<T>) {
+            test_integer_to_chars(static_cast<T>(-1), base, "-1");
+
+            for (const auto& p : output_negative) {
+                if (p.first >= static_cast<int64_t>(numeric_limits<T>::min())) {
+                    test_integer_to_chars(static_cast<T>(p.first), base, p.second[static_cast<size_t>(base)]);
+                }
+            }
+        }
+    }
+
+    test_integer_to_chars(static_cast<T>(42), nullopt, "42");
+}
+
+enum class TestFromCharsMode { Normal, SignalingNaN };
+
+template <typename T, typename BaseOrFmt>
+void test_from_chars(const string_view input, const BaseOrFmt base_or_fmt, const size_t correct_idx,
+    const errc correct_ec, const optional<T> opt_correct = nullopt,
+    const TestFromCharsMode mode = TestFromCharsMode::Normal) {
+
+    if constexpr (is_integral_v<T>) {
+        assert(mode == TestFromCharsMode::Normal);
+    }
+
+    constexpr T unmodified = 111;
+
+    T dest = unmodified;
+
+    const from_chars_result result = from_chars(input.data(), input.data() + input.size(), dest, base_or_fmt);
+
+    assert(result.ptr == input.data() + correct_idx);
+    assert(result.ec == correct_ec);
+
+    if (correct_ec == errc{} || (is_floating_point_v<T> && correct_ec == errc::result_out_of_range)) {
+        if constexpr (is_floating_point_v<T>) {
+            if (mode == TestFromCharsMode::Normal) {
+                using Uint = conditional_t<is_same_v<T, float>, uint32_t, uint64_t>;
+                assert(opt_correct.has_value());
+                assert(_Bit_cast<Uint>(dest) == _Bit_cast<Uint>(opt_correct.value()));
+            } else {
+                assert(mode == TestFromCharsMode::SignalingNaN);
+                assert(!opt_correct.has_value());
+                assert(isnan(dest));
+            }
+        } else {
+            assert(opt_correct.has_value());
+            assert(dest == opt_correct.value());
+        }
+    } else {
+        assert(!opt_correct.has_value());
+        assert(dest == unmodified);
+    }
+}
+
+constexpr errc inv_arg = errc::invalid_argument;
+constexpr errc out_ran = errc::result_out_of_range;
+
+template <typename T>
+void test_integer_from_chars() {
+    for (int base = 2; base <= 36; ++base) {
+        test_from_chars<T>("", base, 0, inv_arg); // no characters
+        test_from_chars<T>("@1", base, 0, inv_arg); // '@' is bogus
+        test_from_chars<T>(".1", base, 0, inv_arg); // '.' is bogus, for integers
+        test_from_chars<T>("+1", base, 0, inv_arg); // '+' is bogus, N4713 23.20.3 [charconv.from.chars]/3
+                                                    // "a minus sign is the only sign that may appear"
+        test_from_chars<T>(" 1", base, 0, inv_arg); // ' ' is bogus, no whitespace in subject sequence
+
+        if constexpr (is_unsigned_v<T>) { // N4713 23.20.3 [charconv.from.chars]/3
+            test_from_chars<T>("-1", base, 0, inv_arg); // "and only if value has a signed type"
+        }
+
+        // N4713 23.20.3 [charconv.from.chars]/1 "[ Note: If the pattern allows for an optional sign,
+        // but the string has no digit characters following the sign, no characters match the pattern. -end note ]"
+        test_from_chars<T>("-", base, 0, inv_arg); // '-' followed by no characters
+        test_from_chars<T>("-@1", base, 0, inv_arg); // '-' followed by bogus '@'
+        test_from_chars<T>("-.1", base, 0, inv_arg); // '-' followed by bogus '.'
+        test_from_chars<T>("-+1", base, 0, inv_arg); // '-' followed by bogus '+'
+        test_from_chars<T>("- 1", base, 0, inv_arg); // '-' followed by bogus ' '
+        test_from_chars<T>("--1", base, 0, inv_arg); // '-' can't be repeated
+
+        vector<char> bogus_digits;
+
+        if (base < 10) {
+            bogus_digits = {static_cast<char>('0' + base), 'A', 'a'};
+        } else {
+            // '[' and '{' are bogus for base 36
+            bogus_digits = {static_cast<char>('A' + (base - 10)), static_cast<char>('a' + (base - 10))};
+        }
+
+        for (const auto& bogus : bogus_digits) {
+            test_from_chars<T>(bogus + "1"s, base, 0, inv_arg); // bogus digit (for this base)
+            test_from_chars<T>("-"s + bogus + "1"s, base, 0, inv_arg); // '-' followed by bogus digit
+        }
+
+        // Test leading zeroes.
+        test_from_chars<T>(string(100, '0'), base, 100, errc{}, static_cast<T>(0));
+        test_from_chars<T>(string(100, '0') + "11"s, base, 102, errc{}, static_cast<T>(base + 1));
+
+        // Test negative zero and negative leading zeroes.
+        if constexpr (is_signed_v<T>) {
+            test_from_chars<T>("-0", base, 2, errc{}, static_cast<T>(0));
+            test_from_chars<T>("-"s + string(100, '0'), base, 101, errc{}, static_cast<T>(0));
+            test_from_chars<T>("-"s + string(100, '0') + "11"s, base, 103, errc{}, static_cast<T>(-base - 1));
+        }
+
+        // N4713 23.20.3 [charconv.from.chars]/1 "The member ptr of the return value points to the
+        // first character not matching the pattern, or has the value last if all characters match."
+        test_from_chars<T>("11", base, 2, errc{}, static_cast<T>(base + 1));
+        test_from_chars<T>("11@@@", base, 2, errc{}, static_cast<T>(base + 1));
+
+        // When overflowing, we need to keep consuming valid digits, in order to return ptr correctly.
+        test_from_chars<T>(string(100, '1'), base, 100, out_ran);
+        test_from_chars<T>(string(100, '1') + "@@@"s, base, 100, out_ran);
+
+        if constexpr (is_signed_v<T>) {
+            test_from_chars<T>("-"s + string(100, '1'), base, 101, out_ran);
+            test_from_chars<T>("-"s + string(100, '1') + "@@@"s, base, 101, out_ran);
+        }
+    }
+
+    // N4713 23.20.3 [charconv.from.chars]/3 "The pattern is the expected form of the subject sequence
+    // in the "C" locale for the given nonzero base, as described for strtol"
+    // C11 7.22.1.4/3 "The letters from a (or A) through z (or Z) are ascribed the values 10 through 35"
+    for (int i = 0; i < 26; ++i) {
+        test_from_chars<T>(string(1, static_cast<char>('A' + i)), 36, 1, errc{}, static_cast<T>(10 + i));
+        test_from_chars<T>(string(1, static_cast<char>('a' + i)), 36, 1, errc{}, static_cast<T>(10 + i));
+    }
+
+    // N4713 23.20.3 [charconv.from.chars]/3 "no "0x" or "0X" prefix shall appear if the value of base is 16"
+    test_from_chars<T>("0x1729", 16, 1, errc{}, static_cast<T>(0)); // reads '0', stops at 'x'
+    test_from_chars<T>("0X1729", 16, 1, errc{}, static_cast<T>(0)); // reads '0', stops at 'X'
+
+    if constexpr (is_signed_v<T>) {
+        test_from_chars<T>("-0x1729", 16, 2, errc{}, static_cast<T>(0)); // reads "-0", stops at 'x'
+        test_from_chars<T>("-0X1729", 16, 2, errc{}, static_cast<T>(0)); // reads "-0", stops at 'X'
+    }
+}
+
+template <typename T>
+void test_integer() {
+    test_integer_to_chars<T>();
+    test_integer_from_chars<T>();
+}
+
+void all_integer_tests() {
+    test_integer<char>();
+    test_integer<signed char>();
+    test_integer<unsigned char>();
+    test_integer<short>();
+    test_integer<unsigned short>();
+    test_integer<int>();
+    test_integer<unsigned int>();
+    test_integer<long>();
+    test_integer<unsigned long>();
+    test_integer<long long>();
+    test_integer<unsigned long long>();
+
+    // Test overflow scenarios.
+    test_from_chars<unsigned int>("4294967289", 10, 10, errc{}, 4294967289U); // not risky
+    test_from_chars<unsigned int>("4294967294", 10, 10, errc{}, 4294967294U); // risky with good digit
+    test_from_chars<unsigned int>("4294967295", 10, 10, errc{}, 4294967295U); // risky with max digit
+    test_from_chars<unsigned int>("4294967296", 10, 10, out_ran); // risky with bad digit
+    test_from_chars<unsigned int>("4294967300", 10, 10, out_ran); // beyond risky
+
+    test_from_chars<int>("2147483639", 10, 10, errc{}, 2147483639); // not risky
+    test_from_chars<int>("2147483646", 10, 10, errc{}, 2147483646); // risky with good digit
+    test_from_chars<int>("2147483647", 10, 10, errc{}, 2147483647); // risky with max digit
+    test_from_chars<int>("2147483648", 10, 10, out_ran); // risky with bad digit
+    test_from_chars<int>("2147483650", 10, 10, out_ran); // beyond risky
+
+    test_from_chars<int>("-2147483639", 10, 11, errc{}, -2147483639); // not risky
+    test_from_chars<int>("-2147483647", 10, 11, errc{}, -2147483647); // risky with good digit
+    test_from_chars<int>("-2147483648", 10, 11, errc{}, -2147483647 - 1); // risky with max digit
+    test_from_chars<int>("-2147483649", 10, 11, out_ran); // risky with bad digit
+    test_from_chars<int>("-2147483650", 10, 11, out_ran); // beyond risky
+}
+
+void assert_message_bits(const bool b, const char* const msg, const uint32_t bits) {
+    if (!b) {
+        fprintf(stderr, "%s failed for 0x%08X\n", msg, bits);
+        fprintf(stderr, "This is a randomized test.\n");
+        fprintf(stderr, "DO NOT IGNORE/RERUN THIS FAILURE.\n");
+        fprintf(stderr, "You must report it to the STL maintainers.\n");
+        abort();
+    }
+}
+
+void assert_message_bits(const bool b, const char* const msg, const uint64_t bits) {
+    if (!b) {
+        // libc++ uses long for 64-bit values.
+        fprintf(stderr, "%s failed for 0x%016llX\n", msg, static_cast<unsigned long long>(bits));
+        fprintf(stderr, "This is a randomized test.\n");
+        fprintf(stderr, "DO NOT IGNORE/RERUN THIS FAILURE.\n");
+        fprintf(stderr, "You must report it to the STL maintainers.\n");
+        abort();
+    }
+}
+
+constexpr uint32_t FractionBits = 10; // Tunable for test coverage vs. performance.
+static_assert(FractionBits >= 1, "Must test at least 1 fraction bit.");
+static_assert(FractionBits <= 23, "There are only 23 fraction bits in a float.");
+
+constexpr uint32_t Fractions = 1U << FractionBits;
+constexpr uint32_t Mask32    = ~((1U << FractionBits) - 1U);
+constexpr uint64_t Mask64    = ~((1ULL << FractionBits) - 1ULL);
+
+constexpr uint32_t PrefixesToTest = 100; // Tunable for test coverage vs. performance.
+static_assert(PrefixesToTest >= 1, "Must test at least 1 prefix.");
+
+constexpr uint32_t PrefixLimit = 2 // sign bit
+                               * 255 // non-INF/NAN exponents for float
+                               * (1U << (23 - FractionBits)); // fraction bits in prefix
+static_assert(PrefixesToTest <= PrefixLimit, "Too many prefixes.");
+
+template <bool IsDouble>
+void test_floating_prefix(const conditional_t<IsDouble, uint64_t, uint32_t> prefix) {
+
+    using UIntType     = conditional_t<IsDouble, uint64_t, uint32_t>;
+    using FloatingType = conditional_t<IsDouble, double, float>;
+
+    // "-1.2345678901234567e-100" or "-1.23456789e-10"
+    constexpr size_t buffer_size = IsDouble ? 24 : 15;
+    char buffer[buffer_size];
+// TODO Enable once std::from_chars has floating point support.
+#if 0
+    FloatingType val;
+#endif
+
+    // Exact sizes are difficult to prove for fixed notation.
+    // This must be at least (IsDouble ? 327 : 48), and I suspect that that's exact.
+    // Here's a loose upper bound:
+    // 1 character for a negative sign
+    // + 325 (for double; 46 for float) characters in the "0.000~~~000" prefix of the min subnormal
+    // + 17 (for double; 9 for float) characters for round-trip digits
+    constexpr size_t fixed_buffer_size = IsDouble ? 1 + 325 + 17 : 1 + 46 + 9;
+    char fixed_buffer[fixed_buffer_size];
+
+    // worst case: negative sign + max normal + null terminator
+    constexpr size_t stdio_buffer_size = 1 + (IsDouble ? 309 : 39) + 1;
+    char stdio_buffer[stdio_buffer_size];
+
+    for (uint32_t frac = 0; frac < Fractions; ++frac) {
+        const UIntType bits      = prefix + frac;
+        const FloatingType input = _Bit_cast<FloatingType>(bits);
+
+        {
+            const auto to_result = to_chars(buffer, end(buffer), input, chars_format::scientific);
+            assert_message_bits(to_result.ec == errc{}, "to_result.ec", bits);
+// TODO Enable once std::from_chars has floating point support.
+#if 0
+            const char* const last = to_result.ptr;
+
+            const auto from_result = from_chars(buffer, last, val);
+
+            assert_message_bits(from_result.ptr == last, "from_result.ptr", bits);
+            assert_message_bits(from_result.ec == errc{}, "from_result.ec", bits);
+            assert_message_bits(_Bit_cast<UIntType>(val) == bits, "round-trip", bits);
+#endif
+        }
+
+        {
+            // Also verify that to_chars() and sprintf_s() emit the same output for integers in fixed notation.
+            const auto fixed_result = to_chars(fixed_buffer, end(fixed_buffer), input, chars_format::fixed);
+            assert_message_bits(fixed_result.ec == errc{}, "fixed_result.ec", bits);
+            const string_view fixed_sv(fixed_buffer, static_cast<size_t>(fixed_result.ptr - fixed_buffer));
+
+            if (find(fixed_sv.begin(), fixed_sv.end(), '.') == fixed_sv.end()) {
+                const int stdio_ret = sprintf_s(stdio_buffer, size(stdio_buffer), "%.0f", input);
+                assert_message_bits(stdio_ret != -1, "stdio_ret", bits);
+                const string_view stdio_sv(stdio_buffer);
+                assert_message_bits(fixed_sv == stdio_sv, "fixed_sv", bits);
+            }
+        }
+    }
+}
+
+template <bool IsDouble>
+void test_floating_hex_prefix(const conditional_t<IsDouble, uint64_t, uint32_t> prefix) {
+
+    using UIntType     = conditional_t<IsDouble, uint64_t, uint32_t>;
+    using FloatingType = conditional_t<IsDouble, double, float>;
+
+    // The precision is the number of hexits after the decimal point.
+    // These hexits correspond to the explicitly stored fraction bits.
+    // double explicitly stores 52 fraction bits. 52 / 4 == 13, so we need 13 hexits.
+    // float explicitly stores 23 fraction bits. 23 / 4 == 5.75, so we need 6 hexits.
+
+    // "-1.fffffffffffffp+1023" or "-1.fffffep+127"
+    constexpr size_t buffer_size = IsDouble ? 22 : 14;
+    char buffer[buffer_size];
+// TODO Enable once std::from_chars has floating point support.
+#if 0
+    FloatingType val;
+#endif
+
+    for (uint32_t frac = 0; frac < Fractions; ++frac) {
+        const UIntType bits      = prefix + frac;
+        const FloatingType input = _Bit_cast<FloatingType>(bits);
+
+        const auto to_result = to_chars(buffer, end(buffer), input, chars_format::hex);
+        assert_message_bits(to_result.ec == errc{}, "(hex) to_result.ec", bits);
+// TODO Enable once std::from_chars has floating point support.
+#if 0
+        const char* const last = to_result.ptr;
+
+        const auto from_result = from_chars(buffer, last, val, chars_format::hex);
+
+        assert_message_bits(from_result.ptr == last, "(hex) from_result.ptr", bits);
+        assert_message_bits(from_result.ec == errc{}, "(hex) from_result.ec", bits);
+        assert_message_bits(_Bit_cast<UIntType>(val) == bits, "(hex) round-trip", bits);
+#endif
+    }
+}
+
+template <bool IsDouble>
+void test_floating_precision_prefix(const conditional_t<IsDouble, uint64_t, uint32_t> prefix) {
+
+    using UIntType     = conditional_t<IsDouble, uint64_t, uint32_t>;
+    using FloatingType = conditional_t<IsDouble, double, float>;
+
+    // Precision for min subnormal in fixed notation. (More than enough for scientific notation.)
+    constexpr int precision = IsDouble ? 1074 : 149;
+
+    // Number of digits for max normal in fixed notation.
+    constexpr int max_integer_length = IsDouble ? 309 : 39;
+
+    // Size for fixed notation. (More than enough for scientific notation.)
+    constexpr size_t charconv_buffer_size = 1 // negative sign
+                                          + max_integer_length // integer digits
+                                          + 1 // decimal point
+                                          + precision; // fractional digits
+    char charconv_buffer[charconv_buffer_size];
+
+    constexpr size_t stdio_buffer_size = charconv_buffer_size + 1; // null terminator
+    char stdio_buffer[stdio_buffer_size];
+
+    // 1 character for a negative sign
+    // + worst cases: 0x1.fffffffffffffp-1022 and 0x1.fffffep-126f
+    constexpr size_t general_buffer_size = 1 + (IsDouble ? 773 : 117);
+    char general_buffer[general_buffer_size];
+    char general_stdio_buffer[general_buffer_size + 1]; // + null terminator
+
+    for (uint32_t frac = 0; frac < Fractions; ++frac) {
+        const UIntType bits      = prefix + frac;
+        const FloatingType input = _Bit_cast<FloatingType>(bits);
+
+        auto result = to_chars(charconv_buffer, end(charconv_buffer), input, chars_format::fixed, precision);
+        assert_message_bits(result.ec == errc{}, "to_chars fixed precision", bits);
+        string_view charconv_sv(charconv_buffer, static_cast<size_t>(result.ptr - charconv_buffer));
+
+        int stdio_ret = sprintf_s(stdio_buffer, size(stdio_buffer), "%.*f", precision, input);
+        assert_message_bits(stdio_ret != -1, "sprintf_s fixed precision", bits);
+        string_view stdio_sv(stdio_buffer);
+
+        assert_message_bits(charconv_sv == stdio_sv, "fixed precision output", bits);
+
+
+        result = to_chars(charconv_buffer, end(charconv_buffer), input, chars_format::scientific, precision);
+        assert_message_bits(result.ec == errc{}, "to_chars scientific precision", bits);
+        charconv_sv = string_view(charconv_buffer, static_cast<size_t>(result.ptr - charconv_buffer));
+
+        stdio_ret = sprintf_s(stdio_buffer, size(stdio_buffer), "%.*e", precision, input);
+        assert_message_bits(stdio_ret != -1, "sprintf_s scientific precision", bits);
+        stdio_sv = stdio_buffer;
+
+        assert_message_bits(charconv_sv == stdio_sv, "scientific precision output", bits);
+
+
+        result = to_chars(general_buffer, end(general_buffer), input, chars_format::general, 5000);
+        assert_message_bits(result.ec == errc{}, "to_chars general precision", bits);
+        charconv_sv = string_view(general_buffer, static_cast<size_t>(result.ptr - general_buffer));
+
+        stdio_ret = sprintf_s(general_stdio_buffer, size(general_stdio_buffer), "%.5000g", input);
+        assert_message_bits(stdio_ret != -1, "sprintf_s general precision", bits);
+        stdio_sv = general_stdio_buffer;
+
+        assert_message_bits(charconv_sv == stdio_sv, "general precision output", bits);
+    }
+}
+
+void test_floating_prefixes(mt19937_64& mt64) {
+    {
+        set<uint64_t> prefixes64;
+
+        while (prefixes64.size() < PrefixesToTest) {
+            const uint64_t val = mt64();
+
+            if ((val & 0x7FF0000000000000ULL) != 0x7FF0000000000000ULL) { // skip INF/NAN
+                prefixes64.insert(val & Mask64);
+            }
+        }
+
+        for (const auto& prefix : prefixes64) {
+            test_floating_prefix<true>(prefix);
+            test_floating_precision_prefix<true>(prefix);
+        }
+
+        test_floating_hex_prefix<true>(*prefixes64.begin()); // save time by testing fewer hexfloats
+    }
+
+    {
+        set<uint32_t> prefixes32;
+
+        while (prefixes32.size() < PrefixesToTest) {
+            const uint32_t val = static_cast<uint32_t>(mt64());
+
+            if ((val & 0x7F800000U) != 0x7F800000U) { // skip INF/NAN
+                prefixes32.insert(val & Mask32);
+            }
+        }
+
+        for (const auto& prefix : prefixes32) {
+            test_floating_prefix<false>(prefix);
+            test_floating_precision_prefix<false>(prefix);
+        }
+
+        test_floating_hex_prefix<false>(*prefixes32.begin()); // save time by testing fewer hexfloats
+    }
+}
+
+// TODO Enable once std::from_chars has floating point support.
+#if 0
+template <typename T>
+void test_floating_from_chars(const chars_format fmt) {
+    test_from_chars<T>("", fmt, 0, inv_arg); // no characters
+    test_from_chars<T>("@1", fmt, 0, inv_arg); // '@' is bogus
+    test_from_chars<T>("z1", fmt, 0, inv_arg); // 'z' is bogus
+    test_from_chars<T>(".", fmt, 0, inv_arg); // '.' without digits is bogus
+    test_from_chars<T>("+1", fmt, 0, inv_arg); // '+' is bogus
+    test_from_chars<T>(" 1", fmt, 0, inv_arg); // ' ' is bogus
+    test_from_chars<T>("p5", fmt, 0, inv_arg); // binary-exponent-part without digits is bogus
+    test_from_chars<T>("in", fmt, 0, inv_arg); // incomplete inf is bogus
+    test_from_chars<T>("na", fmt, 0, inv_arg); // incomplete nan is bogus
+
+    test_from_chars<T>("-", fmt, 0, inv_arg); // '-' followed by no characters
+    test_from_chars<T>("-@1", fmt, 0, inv_arg); // '-' followed by bogus '@'
+    test_from_chars<T>("-z1", fmt, 0, inv_arg); // '-' followed by bogus 'z'
+    test_from_chars<T>("-.", fmt, 0, inv_arg); // '-' followed by bogus '.'
+    test_from_chars<T>("-+1", fmt, 0, inv_arg); // '-' followed by bogus '+'
+    test_from_chars<T>("- 1", fmt, 0, inv_arg); // '-' followed by bogus ' '
+    test_from_chars<T>("-p5", fmt, 0, inv_arg); // '-' followed by bogus binary-exponent-part
+    test_from_chars<T>("-in", fmt, 0, inv_arg); // '-' followed by bogus incomplete inf
+    test_from_chars<T>("-na", fmt, 0, inv_arg); // '-' followed by bogus incomplete nan
+    test_from_chars<T>("--1", fmt, 0, inv_arg); // '-' can't be repeated
+
+    if (fmt != chars_format::hex) { // "e5" are valid hexits
+        test_from_chars<T>("e5", fmt, 0, inv_arg); // exponent-part without digits is bogus
+        test_from_chars<T>("-e5", fmt, 0, inv_arg); // '-' followed by bogus exponent-part
+    }
+
+    constexpr T inf  = numeric_limits<T>::infinity();
+    constexpr T qnan = numeric_limits<T>::quiet_NaN();
+
+    test_from_chars<T>("InF", fmt, 3, errc{}, inf);
+    test_from_chars<T>("infinite", fmt, 3, errc{}, inf);
+    test_from_chars<T>("iNfInItY", fmt, 8, errc{}, inf);
+    test_from_chars<T>("InfinityMeow", fmt, 8, errc{}, inf);
+
+    test_from_chars<T>("-InF", fmt, 4, errc{}, -inf);
+    test_from_chars<T>("-infinite", fmt, 4, errc{}, -inf);
+    test_from_chars<T>("-iNfInItY", fmt, 9, errc{}, -inf);
+    test_from_chars<T>("-InfinityMeow", fmt, 9, errc{}, -inf);
+
+    test_from_chars<T>("NaN", fmt, 3, errc{}, qnan);
+    test_from_chars<T>("nanotech", fmt, 3, errc{}, qnan);
+    test_from_chars<T>("nan(", fmt, 3, errc{}, qnan);
+    test_from_chars<T>("nan(@)", fmt, 3, errc{}, qnan);
+    test_from_chars<T>("nan(()", fmt, 3, errc{}, qnan);
+    test_from_chars<T>("nan(abc", fmt, 3, errc{}, qnan);
+    test_from_chars<T>("nan()", fmt, 5, errc{}, qnan);
+    test_from_chars<T>("nan(abc)def", fmt, 8, errc{}, qnan);
+    test_from_chars<T>("nan(_09AZaz)", fmt, 12, errc{}, qnan);
+    test_from_chars<T>("nan(int)", fmt, 8, errc{}, qnan);
+    test_from_chars<T>("nan(snap)", fmt, 9, errc{}, qnan);
+
+    test_from_chars<T>("-NaN", fmt, 4, errc{}, -qnan);
+    test_from_chars<T>("-nanotech", fmt, 4, errc{}, -qnan);
+    test_from_chars<T>("-nan(", fmt, 4, errc{}, -qnan);
+    test_from_chars<T>("-nan(@)", fmt, 4, errc{}, -qnan);
+    test_from_chars<T>("-nan(()", fmt, 4, errc{}, -qnan);
+    test_from_chars<T>("-nan(abc", fmt, 4, errc{}, -qnan);
+    test_from_chars<T>("-nan()", fmt, 6, errc{}, -qnan);
+    test_from_chars<T>("-nan(abc)def", fmt, 9, errc{}, -qnan);
+    test_from_chars<T>("-nan(_09AZaz)", fmt, 13, errc{}, -qnan);
+    test_from_chars<T>("-nan(int)", fmt, 9, errc{}, -qnan);
+    test_from_chars<T>("-nan(snap)", fmt, 10, errc{}, -qnan);
+
+    // The UCRT considers indeterminate NaN to be negative quiet NaN with no payload bits set.
+    // It parses "nan(ind)" and "-nan(ind)" identically.
+    test_from_chars<T>("nan(InD)", fmt, 8, errc{}, -qnan);
+    test_from_chars<T>("-nan(InD)", fmt, 9, errc{}, -qnan);
+
+    test_from_chars<T>("nan(SnAn)", fmt, 9, errc{}, nullopt, TestFromCharsMode::SignalingNaN);
+    test_from_chars<T>("-nan(SnAn)", fmt, 10, errc{}, nullopt, TestFromCharsMode::SignalingNaN);
+
+    switch (fmt) {
+    case chars_format::general:
+        test_from_chars<T>("1729", fmt, 4, errc{}, T{1729});
+        test_from_chars<T>("1729e3", fmt, 6, errc{}, T{1729000});
+        test_from_chars<T>("10", fmt, 2, errc{}, T{10});
+        test_from_chars<T>("11.", fmt, 3, errc{}, T{11});
+        test_from_chars<T>("12.13", fmt, 5, errc{}, static_cast<T>(12.13)); // avoid truncation warning
+        test_from_chars<T>(".14", fmt, 3, errc{}, static_cast<T>(.14)); // avoid truncation warning
+        test_from_chars<T>("20e5", fmt, 4, errc{}, T{2000000});
+        test_from_chars<T>("21.e5", fmt, 5, errc{}, T{2100000});
+        test_from_chars<T>("22.23e5", fmt, 7, errc{}, T{2223000});
+        test_from_chars<T>(".24e5", fmt, 5, errc{}, T{24000});
+        test_from_chars<T>("33e+5", fmt, 5, errc{}, T{3300000});
+        test_from_chars<T>("33e-5", fmt, 5, errc{}, static_cast<T>(.00033)); // avoid truncation warning
+        test_from_chars<T>("4E7", fmt, 3, errc{}, T{40000000});
+        test_from_chars<T>("-00123abc", fmt, 6, errc{}, T{-123});
+        test_from_chars<T>(".0045000", fmt, 8, errc{}, static_cast<T>(.0045)); // avoid truncation warning
+        test_from_chars<T>("000", fmt, 3, errc{}, T{0});
+        test_from_chars<T>("0e9999", fmt, 6, errc{}, T{0});
+        test_from_chars<T>("0e-9999", fmt, 7, errc{}, T{0});
+        test_from_chars<T>("-000", fmt, 4, errc{}, T{-0.0});
+        test_from_chars<T>("-0e9999", fmt, 7, errc{}, T{-0.0});
+        test_from_chars<T>("-0e-9999", fmt, 8, errc{}, T{-0.0});
+        test_from_chars<T>("1e9999", fmt, 6, errc::result_out_of_range, inf);
+        test_from_chars<T>("-1e9999", fmt, 7, errc::result_out_of_range, -inf);
+        test_from_chars<T>("1e-9999", fmt, 7, errc::result_out_of_range, T{0});
+        test_from_chars<T>("-1e-9999", fmt, 8, errc::result_out_of_range, T{-0.0});
+        test_from_chars<T>("1" + string(6000, '0'), fmt, 6001, errc::result_out_of_range, inf);
+        test_from_chars<T>("-1" + string(6000, '0'), fmt, 6002, errc::result_out_of_range, -inf);
+        test_from_chars<T>("." + string(6000, '0') + "1", fmt, 6002, errc::result_out_of_range, T{0});
+        test_from_chars<T>("-." + string(6000, '0') + "1", fmt, 6003, errc::result_out_of_range, T{-0.0});
+        test_from_chars<T>("1" + string(500, '0'), fmt, 501, errc::result_out_of_range, inf);
+        test_from_chars<T>("-1" + string(500, '0'), fmt, 502, errc::result_out_of_range, -inf);
+        test_from_chars<T>("." + string(500, '0') + "1", fmt, 502, errc::result_out_of_range, T{0});
+        test_from_chars<T>("-." + string(500, '0') + "1", fmt, 503, errc::result_out_of_range, T{-0.0});
+        break;
+    case chars_format::scientific:
+        test_from_chars<T>("1729", fmt, 0, inv_arg);
+        test_from_chars<T>("1729e3", fmt, 6, errc{}, T{1729000});
+        break;
+    case chars_format::fixed:
+        test_from_chars<T>("1729", fmt, 4, errc{}, T{1729});
+        test_from_chars<T>("1729e3", fmt, 4, errc{}, T{1729});
+        break;
+    case chars_format::hex:
+        test_from_chars<T>("0x123", fmt, 1, errc{}, T{0});
+        test_from_chars<T>("a0", fmt, 2, errc{}, T{160});
+        test_from_chars<T>("a1.", fmt, 3, errc{}, T{161});
+        test_from_chars<T>("a2.a3", fmt, 5, errc{}, T{162.63671875});
+        test_from_chars<T>(".a4", fmt, 3, errc{}, T{0.640625});
+        test_from_chars<T>("a0p5", fmt, 4, errc{}, T{5120});
+        test_from_chars<T>("a1.p5", fmt, 5, errc{}, T{5152});
+        test_from_chars<T>("a2.a3p5", fmt, 7, errc{}, T{5204.375});
+        test_from_chars<T>(".a4p5", fmt, 5, errc{}, T{20.5});
+        test_from_chars<T>("a0p+5", fmt, 5, errc{}, T{5120});
+        test_from_chars<T>("a0p-5", fmt, 5, errc{}, T{5});
+        test_from_chars<T>("ABCDEFP3", fmt, 8, errc{}, T{90075000});
+        test_from_chars<T>("-00cdrom", fmt, 5, errc{}, T{-205});
+        test_from_chars<T>(".00ef000", fmt, 8, errc{}, T{0.0036468505859375});
+        test_from_chars<T>("000", fmt, 3, errc{}, T{0});
+        test_from_chars<T>("0p9999", fmt, 6, errc{}, T{0});
+        test_from_chars<T>("0p-9999", fmt, 7, errc{}, T{0});
+        test_from_chars<T>("-000", fmt, 4, errc{}, T{-0.0});
+        test_from_chars<T>("-0p9999", fmt, 7, errc{}, T{-0.0});
+        test_from_chars<T>("-0p-9999", fmt, 8, errc{}, T{-0.0});
+        test_from_chars<T>("1p9999", fmt, 6, errc::result_out_of_range, inf);
+        test_from_chars<T>("-1p9999", fmt, 7, errc::result_out_of_range, -inf);
+        test_from_chars<T>("1p-9999", fmt, 7, errc::result_out_of_range, T{0});
+        test_from_chars<T>("-1p-9999", fmt, 8, errc::result_out_of_range, T{-0.0});
+        test_from_chars<T>("1" + string(2000, '0'), fmt, 2001, errc::result_out_of_range, inf);
+        test_from_chars<T>("-1" + string(2000, '0'), fmt, 2002, errc::result_out_of_range, -inf);
+        test_from_chars<T>("." + string(2000, '0') + "1", fmt, 2002, errc::result_out_of_range, T{0});
+        test_from_chars<T>("-." + string(2000, '0') + "1", fmt, 2003, errc::result_out_of_range, T{-0.0});
+        test_from_chars<T>("1" + string(300, '0'), fmt, 301, errc::result_out_of_range, inf);
+        test_from_chars<T>("-1" + string(300, '0'), fmt, 302, errc::result_out_of_range, -inf);
+        test_from_chars<T>("." + string(300, '0') + "1", fmt, 302, errc::result_out_of_range, T{0});
+        test_from_chars<T>("-." + string(300, '0') + "1", fmt, 303, errc::result_out_of_range, T{-0.0});
+        break;
+    }
+}
+#endif
+
+template <typename T>
+void test_floating_to_chars(
+    const T value, const optional<chars_format> opt_fmt, const optional<int> opt_precision, const string_view correct) {
+
+    test_common_to_chars(value, opt_fmt, opt_precision, correct);
+}
+
+void all_floating_tests(mt19937_64& mt64) {
+    test_floating_prefixes(mt64);
+
+// TODO Enable once std::from_chars has floating point support.
+#if 0
+    for (const auto& fmt : {chars_format::general, chars_format::scientific, chars_format::fixed, chars_format::hex}) {
+        test_floating_from_chars<float>(fmt);
+        test_floating_from_chars<double>(fmt);
+    }
+
+    // Test rounding.
+
+    // See float_from_chars_test_cases.hpp in this directory.
+    for (const auto& t : float_from_chars_test_cases) {
+        test_from_chars<float>(t.input, t.fmt, t.correct_idx, t.correct_ec, t.correct_value);
+    }
+
+    // See double_from_chars_test_cases.hpp in this directory.
+    for (const auto& t : double_from_chars_test_cases) {
+        test_from_chars<double>(t.input, t.fmt, t.correct_idx, t.correct_ec, t.correct_value);
+    }
+
+    {
+        // See LWG-2403. This number (exactly 0x1.fffffd00000004 in infinite precision) behaves differently
+        // when parsed as double and converted to float, versus being parsed as float directly.
+        const char* const lwg_2403          = "1.999999821186065729339276231257827021181583404541015625";
+        constexpr float correct_float       = 0x1.fffffep0f;
+        constexpr double correct_double     = 0x1.fffffdp0;
+        constexpr float twice_rounded_float = 0x1.fffffcp0f;
+
+        test_from_chars<float>(lwg_2403, chars_format::general, 56, errc{}, correct_float);
+        test_from_chars<double>(lwg_2403, chars_format::general, 56, errc{}, correct_double);
+        static_assert(static_cast<float>(correct_double) == twice_rounded_float);
+    }
+
+    // See floating_point_test_cases.hpp.
+    for (const auto& p : floating_point_test_cases_float) {
+        test_from_chars<float>(p.first, chars_format::general, strlen(p.first), errc{}, _Bit_cast<float>(p.second));
+    }
+
+    for (const auto& p : floating_point_test_cases_double) {
+        test_from_chars<double>(p.first, chars_format::general, strlen(p.first), errc{}, _Bit_cast<double>(p.second));
+    }
+#endif
+    // See float_to_chars_test_cases.hpp in this directory.
+    for (const auto& t : float_to_chars_test_cases) {
+        if (t.fmt == chars_format{}) {
+            test_floating_to_chars(t.value, nullopt, nullopt, t.correct);
+        } else {
+            test_floating_to_chars(t.value, t.fmt, nullopt, t.correct);
+        }
+    }
+
+    // See double_to_chars_test_cases.hpp in this directory.
+    for (const auto& t : double_to_chars_test_cases) {
+        if (t.fmt == chars_format{}) {
+            test_floating_to_chars(t.value, nullopt, nullopt, t.correct);
+        } else {
+            test_floating_to_chars(t.value, t.fmt, nullopt, t.correct);
+        }
+    }
+
+    // See corresponding headers in this directory.
+    for (const auto& t : float_hex_precision_to_chars_test_cases) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : float_fixed_precision_to_chars_test_cases) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : float_scientific_precision_to_chars_test_cases) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : float_general_precision_to_chars_test_cases) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_hex_precision_to_chars_test_cases) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_fixed_precision_to_chars_test_cases_1) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_fixed_precision_to_chars_test_cases_2) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_fixed_precision_to_chars_test_cases_3) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_fixed_precision_to_chars_test_cases_4) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_scientific_precision_to_chars_test_cases_1) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_scientific_precision_to_chars_test_cases_2) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_scientific_precision_to_chars_test_cases_3) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_scientific_precision_to_chars_test_cases_4) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+    for (const auto& t : double_general_precision_to_chars_test_cases) {
+        test_floating_to_chars(t.value, t.fmt, t.precision, t.correct);
+    }
+}
+
+int main(int argc, char** argv) {
+    const auto start = chrono::steady_clock::now();
+
+    mt19937_64 mt64;
+
+    initialize_randomness(mt64, argc, argv);
+
+    all_integer_tests();
+
+    all_floating_tests(mt64);
+
+    const auto finish  = chrono::steady_clock::now();
+    const long long ms = chrono::duration_cast<chrono::milliseconds>(finish - start).count();
+
+    puts("PASS");
+    printf("Randomized test cases: %u\n", PrefixesToTest * Fractions);
+    printf("Total time: %lld ms\n", ms);
+
+    if (ms < 3'000) {
+        puts("That was fast. Consider tuning PrefixesToTest and FractionBits to test more cases.");
+    } else if (ms > 30'000) {
+        puts("That was slow. Consider tuning PrefixesToTest and FractionBits to test fewer cases.");
+    }
+}

libcxx/test/std/utilities/charconv/charconv.msvc/test.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++03, c++11, c++14
+
+// to_chars requires functions in the dylib that were introduced in Mac OS 10.15.
+//
+// XFAIL: use_system_cxx_lib && target={{.+}}-apple-macosx10.{{.+}}
+
+// steady_clock requires threads.
+// UNSUPPORTED: libcpp-has-no-threads
+// UNSUPPORTED: libcpp-has-no-random-device
+// UNSUPPORTED: libcpp-has-no-localization
+
+// TODO(ldionne): This test fails on Ubuntu Focal on our CI nodes (and only there), in 32 bit mode.
+// UNSUPPORTED: linux && 32bits-on-64bits
+
+// XFAIL: LIBCXX-AIX-FIXME
+
+// <charconv>
+
+#include <type_traits>
+
+// Work-around for sprintf_s's usage in the Microsoft tests.
+#ifndef _WIN32
+#  define sprintf_s snprintf
+#endif
+
+// FUNCTION TEMPLATE _Bit_cast
+template <class _To, class _From,
+          std::enable_if_t<sizeof(_To) == sizeof(_From) && std::is_trivially_copyable_v<_To> &&
+                               std::is_trivially_copyable_v<_From>,
+                           int> = 0>
+[[nodiscard]] constexpr _To _Bit_cast(const _From& _From_obj) noexcept {
+  return __builtin_bit_cast(_To, _From_obj);
+}
+
+// Includes Microsoft's test that tests the entire header.
+
+#include "test.cpp"