Address more review comments: fix some assertions when extents are 0

I believe this 3-level thing is in general a good idea, and in principle the words "hardened < safe < debug" fell ok-ish to me in terms of expectations how much gets checked.
However, in light of a 3-level mode I may want to rethink for example the asserts in mdspan, and tailor better what is enabled in hardened, vs safe mode. I think the current choices were good in a binary world, in this more nuanced approach I am not sure.

Simply disable deduction guide warnings, adding them explicitly ended up either with unused template warning in files where they are not needed, or with a warning from GCC if one adds [[maybe_unused]], will try separately to make this warning go away.

Add missing test on const mapping for required_span_size

Fix more warning stuff

Fix a formatting thing in tests.

Address review feedback, and implement missing ctors from layout_stride in layout_left/right

This passed testing except the expected AIX failure since the runners are down.

Fix older clang missing a typename in a test

To answer my own question: I was able to reproduce the bug when compiling for NVIDIA GPUs, I was not able to reproduce it for AMD GPUs yet, and I didn't try for Intel GPUs.

Question: does this bug potentially affect code generation for AMD/NVIDIA/Intel GPUs?

Update mdspan std::module file

Fixup module map

More fixes for things not triggered in my various MacOS builds.

Fix ADL use warning.

More formatting fixes in the tests.

Fix up comments for some formatting check.

The mdspan thing that breaks clang-tidy is now fixed,

This landed in https://github.com/llvm/llvm-project/commit/488c3db245ce0fe3b70357d6798ee91c5baa82a2, but was missing in D in the revision URL.

Will ignore the CI failure of the "Module build with local submodule visibility": known common issue with the module cache producing over 1000 errors in the mold of:

bk;t=1690294997920/home/libcxx-builder/.buildkite-agent/builds/google-libcxx-builder-49573bbe06a2-1/llvm-project/libcxx-ci/build/generic-modules-lsv/include/c++/v1/__concepts/regular.h:13:2: fatal error: module file '/home/libcxx-builder/.cache/clang/ModuleCache/1BZ5PZK31RHUI/std_private_concepts_semiregular-1920JD1R2UQK3.pcm' is out of date and needs to be rebuilt

Uploaded the wrong patch file last time around, where I guarded the wrong two tests on MinGW :-(

Apply review comments: specifically don't check index bounds in layout_left/right since it's double checking when used in mdspan.

Sounds good!

Filed issue here: https://github.com/llvm/llvm-project/issues/64077

Work around MinGW issue by disabling test, not removing no-unique-address.

I investigated the failure on MinGW and tracked it down to a reproducer on godbolt, which indicates this is a bug in the compiler when using --target=x86_64-w64-windows-gnu
https://godbolt.org/z/Y6Mb7sMMc

Attempt to fix mingw failure.

Address last comments: make all assertions UNCATEGORIZED

Trigger all mdspan assertions in hardened mode: all of them are related in one form or another to bounds checking. Either directly, or in order to not screw up the bounds during construction/assignment/conversion etc. which would violate the invariants of mdspan, and thus could lead to bounds checks not triggering when they should.

Fix 32bit builds and fix size assertion.

Fix apple clang build ... TEST_CLANG_VER is not defined on apple clang ...

Fix warning on GCC

Fix formatting, add more triviality testing

Added release notes, rebased. Addressed Louis comments.

Another CI fix and add missing static assert verification.

Fix another warning from GCC

Fix CI

This addresses Louis review comments. Most notably fixing a lot of constraints regarding const& vs non-const arguments and adding testing for that.

Addressed all the comments, uploading patch now.

Split too long static_assert test, added some more non-constructibility checks

Fir formating.

Add a few more tests checking for explicitness of constructors, and size of mdspan.

Rebase on main, and adding swap test.

Address last of Louis' comments and rebase.

Add assertion tests

Fix module file and GCC build.

LGTM, but I haven't been here long enough to feel like I can accept this on behalf of libc++ team :-)

Address some review comments, add conversion test.

Fix module map issue which crept in during rebase

This implements about 80% of the necessary tests, but its already a lot of code so we can collect review feedback while we do the rest.

Rebase on top of main

Rebase on top of main.

Apply post-review changes from layout_right to layout_left

Address review comments

Remove unused include in test

Missing include for modules build in test.

Fix another missing include

Fix module include complaint

Fix more formatting stuff.

Fix whitespace in comment in test

Fix include order.

Fix missing include for module build

Fix some copy paste name issues in required_span_size test
Fix whitespace in comments in tests

Fix wrong comment and test name for required_span_size

Fix test which exceeds default consteval step limit, and fix formatting of fwd file.

With assertion enabled one of the tests we expanded in the last commit hit the default maximum step limit in consteval. I split the test now and run the large iteration case only in runtime mode, not in consteval.

Address review comments.

Rebased on top of layout_right revision

Address last comments