lgtm

Confirmed today it solves the problem.

Thank you! It will surely make building easier.

Rebuilt Rust with this patch applied to host LLVM and it still works after stripping binaries and libraries.

LGTM

Looking at Rust's fix over https://github.com/rust-lang/rust/commit/4f0ad1c92ca08da6e8dc17838070975762f59714 seems like there is API added in Windows 10 to solve it (I don't know how effective though).
I'm not going to work on this myself but leaving the link in case somebody else wants to give it a try.

In D68480#3218341, @mstorsjo wrote:

In D68480#3218277, @ldionne wrote:

I will argue that breaking this ABI on Windows is not a big deal since nobody's vending libc++ on Windows. Or at least if they do, they are completely invisible to us ("us" being the people who develop libc++).

Would you be willing to open a patch showing what changes are necessary for each of those? I think we can totally break the ABI on Windows since nobody's shipping it.

I would like to add some nuance to these statements here.

I do ship shared linked libc++ on Windows (as part of the llvm-mingw toolchain distribution), but without any strong ABI guarantees. Ideally ABI wouldn't break between releases, but if it does (especially in a fringe area) it's probably tolerable.

MSYS2 also ships an environment where libc++ is the standard system C++ library, linked shared. That environment is considered somewhat experimental afaik (CC @mati865), so if it breaks some package (which can be fixed by rebuilding), I think they'd consider it tolerable. If none of their packages actually have ended up using and depending on the aspects that may change (I haven't followed closely exactly how widespread it is), the ABI break should be totally transparent though.

There was similar differential recently: https://reviews.llvm.org/D112093

I never had to dig into subsystem versions and what do the mean but looking at subsystem docs 4.0 stands for kernel mode drivers which looks wrong to me. They also specify 5.01 as 32-bit, 5.02 as 64-bit and 6.0 as being either 32-bit or 64-bit.

Agree, we should promote using working and tested configuration.
Even if pthread build works it's probably affected by threading issues when built with GCC.

LGTM

LGTM

LGTM

From a quick look at the options listing, I presume most other cases of S<> and J<…=> should be changed into Eq<> too.

Building only X86 target did the trick and it looks good:

$ ls bin/ | rg libLLVM.*dll
libLLVM-13git.dll

I had no internet during the weekend (massive storms over here) but so I returned to it yesterday.
I'm unable to build clean main branch at the moment:

`
[2972/3064] Linking CXX shared library bin\libLLVM.dll
FAILED: bin/libLLVM.dll lib/libLLVM.dll.a
cmd.exe /C "cd . && D:\msys64\clang64\bin\c++.exe -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wdelete-non-virtual-dtor -Wsuggest-override -Wstring-conversion -Wmisleading-indentation -ffunction-sections -fdata-sections -O3 -DNDEBUG  -Wl,--gc-sections -shared -o bin\libLLVM.dll -Wl,--out-implib,lib\libLLVM.dll.a -Wl,--major-image-version,0,--minor-image-version,0 @CMakeFiles\LLVM.rsp  && cd ."
lld-link: error: too many exported symbols (max 65535)
`

It's simple change though, should I update diff without testing?

LGTM sorry for the delay.

In D89009#2882846, @mstorsjo wrote:

In D89009#2857310, @mati865 wrote:

In D89009#2857228, @mstorsjo wrote:

Yep. I guess the question mainly is if we'd want to make this an upstream thing, adding an if(UNIX) around the symlinks on lines 608-613 here, if windows packaging cases would want to omit them anyway?

I have no idea about guidelines for Windows but it'd make sense for me.

@mati865 - Do you want to update the patch with an if(UNIX) around the symlink lines? I think we've got agreement that we can move forward with this, and it'd be nice to have it in before the 13.x branch in a couple weeks.

In D89009#2857228, @mstorsjo wrote:

Yep. I guess the question mainly is if we'd want to make this an upstream thing, adding an if(UNIX) around the symlinks on lines 608-613 here, if windows packaging cases would want to omit them anyway?

In D89009#2857190, @mstorsjo wrote:

The import libraries do seem to use the right name as far as I can see, but there's another aspect I remembered now: This does create unversioned symlinks too (not while building but once you do ninja install). This probably is neat to have, but for cases when things are packaged up in e.g. zip files or something else that doesn't handle symlinks, one might want not to have them. Within llvm-mingw I guess I can have them stripped out before packaging though.

Thank you for returning to this.
I'd love to get confirmation from @hans who suggested it in https://reviews.llvm.org/D87521 that this still seems like the best approach.

LGTM once D104530 is merged.

LGTM

LGTM

LGTM

Feels a bit like approving myself (which is only partially true) but I don't see any issues with the patch itself.

Ah, so that explains why everyone sends LGTM text.
I'll try to remember it next time.

Wow, I haven't expected that.

Feels like a heavy hammer to me but guess there is no better option.

FWIW at MSYS2 we build LLVM with both GNU and LLVM toolchains for different "subsystems".
GNU's LLD was deadlocking a lot so we have patched it to use TerminateProcess and it worked around all deadlocks except when running tests (the patch probably needs more work on it), we don't apply it for LLVM's LLD because I thought it's a bit overkill.

Funny but I've hit this deadlock (LLVM_LINK_LLVM_DYLIB, LLD_DEFAULT_LD_LLD_IS_MINGW and shared libc++) last week in single LLD unit test. It never reproduced despite dozen of LLD testsuite runs.

When building with ninja, the output is buffered so the warnings appear directly after the specific build target that cause them.

But I don't know if ld.bfd actually implements the -z options for PE targets?

Fix typo and the test

I don't know when they exactly appear but look at my building log: https://reviews.llvm.org/P8263
The build was done with 16 threads so it's hard to tell which objects made it appear.

Sorry I thought it's simple enough on it's own.

The change itself looks correct but cannot speak for the test.

If compiling with GCC or linking with ld.bfd, these options have little

effect

I saw https://github.com/msys2/msys2-runtime/issues/36 but I have never worked with MSYS2 runtime internals so you probably know more than I do at this point.
https://github.com/dscho who maintains Git for Windows might have some insights.

It's clear overlook from D79995, that part is perfectly reasonable to me.

Sorry for the delay.
LGTM from MinGW point of view.

Opened https://reviews.llvm.org/D89225

Or maybe even make it into a cmake option?

Older versions of lld didn't error out if exceeding the limit, this is fixed in D86701, unfortunately after the 11 branch.

With -DLLVM_ENABLE_ASSERTIONS=ON -DCMAKE_C_COMPILER=clang -DCMAKE_CXX_COMPILER=clang++ -DCMAKE_RANLIB_COMPILER=llvm-ranlib -DCMAKE_AR_COMPILER=llvm-ar -DCMAKE_LINKER=ld.lld -DLLVM_ENABLE_LLD=ON libclang-cpp.dll has 65535 exports, seems it got truncated?

Reproduced by adding -DLLVM_ENABLE_ASSERTIONS=ON.

How many exports does your DLL end up with - is it close to the 64k limit, or far from it? Is there maybe some other library that is linked in, that increases the number of exported symbols (=all), or does this DLL only export explicitly intended symbols with dllexport?

@ASDenysPetrov what CMake options do you use?
I'm unable to reproduce this error with Clang+LLD and GCC+Binutils from MSYS2.

I wonder if it'd be possible to add some custom substitution in the lit config, to have it replace ld.lld with ld.lld -m <some-elf> in this case...

With BFD (tested version 2.35) the latter specified option takes precedence:

Nit: according to https://docs.microsoft.com/en-us/cpp/build/reference/subsystem-specify-subsystem?view=vs-2019 the minimal and the default subsystem for ARM should be 6.02.

@hans sorry for not spotting it earlier but is it possible to still backport it to LLVM 11?
It's totally OK if it's too late. I can easily keep it as a patch in MSYS2 repository.

LGTM
Confirmed that GCC 9 still adds .exe.

Sounds great, could you commit it? I don't have the permission.

Cygwin seems to be the only Windows target that adds version to the library names.

Thanks.

Sorry, pasted wrong command. I was curious if import library has it (since static one did not) but in the end neither import nor static library shows any export.

what code appends a version number in dynamic libs when built for other platforms, but decides not to, when targeting windows in general, or mingw specifically?

bin/llvm-readobj --coff-directives lib/liblibclang.dll.a | grep -i export shows nothing.

Could you fix the title+description?

We had this patch at MSYS2 for years and I'm not aware of any issues with the static library.
I think the library looks fine:

$ nm lib/liblibclang.a | grep __imp_
                 U __imp___acrt_iob_func
                 U __imp___acrt_iob_func
                 U __imp_GetModuleFileNameA
                 U __imp_VirtualQuery
                 U __imp___acrt_iob_func
                 U __imp___acrt_iob_func
                 U __imp___acrt_iob_func

I don't use MSVC but apparently there is no libLLVM there: https://github.com/llvm/llvm-project/blob/9c651c231f3144f53e13cd0a1747589e1b2edccd/llvm/tools/llvm-shlib/CMakeLists.txt#L15

-DLLVM_ENABLE_PROJECTS="clang;lldb" -DLLVM_BUILD_LLVM_DYLIB=1 with only this patch applied (< is before, > is after):

$ diff <(cd ../build && find ./ | sort) <(cd ../build2/ && find ./ | sort)
38a39,41
> ./bin/libLLVM.dll
> ./bin/libLTO.dll
> ./bin/libRemarks.dll
51d53
< ./bin/LLVM.dll
119d120
< ./bin/LTO.dll
123d123
< ./bin/Remarks.dll
1460a1461
> ./lib/libclang.dll.a
1500,1501c1501
< ./lib/liblibclang.dll.a
< ./lib/libliblldb.dll.a
---
> ./lib/liblldb.dll.a

I haven't tried BUILD_SHARED_LIBS=TRUE TBH.

Also adjusted llvm-config.

Updated the diff.

How widespread are these build systems that parse help output? (Given that it took until now to discover them, I'd venture "not very".)