[libcxx-commits] [PATCH] D112112: [libunwind] Link with -unwindlib=none

[Harald van Dijk via Phabricator via libcxx-commits]

hvdijk added a comment.

In D112112#3076215 <https://reviews.llvm.org/D112112#3076215>, @mstorsjo wrote:

> Ah, I see. Can you try by adding `-DCMAKE_C_COMPILER_WORKS=TRUE -DCMAKE_CXX_COMPILER_WORKS=TRUE`? That waives this particular failure.

I tried that at first (for both compiler-rt and libunwind -- I don't think we should be using different workarounds for the two), that breaks in a different way:

  CMake Error at cmake/config-ix.cmake:197 (message):
    Please use architecture with 4 or 8 byte pointers.
  Call Stack (most recent call first):
    CMakeLists.txt:251 (include)

This happens because simply telling CMake that linking  works will make CMake assume that linking works. It then uses linking in all of its detection steps, so all of its detection steps fail.

> `-DCMAKE_TRY_COMPILE_TARGET_TYPE=STATIC_LIBRARY` is too blunt an instrument for this, for my configurations (targeting mingw). If I build libunwind with that set, linking the shared libunwind fails with these errors:
>
>   lld: error: unable to find library -lc
>   lld: error: unable to find library -ldl
>   lld: error: unable to find library -ldl
>
> Because libunwind does have checks for whether e.g. `-lc` and `-ldl` work, and these give false positives with that setting.

Thanks for the explanation, will have a think about how we can have things work for both of us.


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https://reviews.llvm.org/D112112