[cfe-dev] Libcxx cmake warning "Host compiler must support std::atomic!"

[Brian M. Rzycki via cfe-dev]

Hello Krzysztof,

I've seen these errors in our nightly builds as well and noticed them when
tracking down a different set of build breaks last month. I don't honestly
know if they can be safely ignored. Our nightly compilers work for our
testing even with the errors. I would be interested in knowing what this
means and if it impacts us though.

I did a little digging and found when we started seeing the messages. These
SHAs are from the LLVM monorepo (https://github.com/llvm/llvm-project.git).
We started seeing them in our builds 2019-March-05. I don't have the exact
commit but may have time tomorrow to dig in a bit more.

b306ef12f04635-master (llvm-svn: 355299) # clean
81dbc02671b223-master (llvm-svn: 355375) # emits "Host compiler must
support std::atomic!"


On Wed, Mar 27, 2019 at 1:20 PM Krzysztof Parzyszek via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> I'm seeing the following warning during cmake. I'm not sure when it
> started. Is this a known issue? Can it be safely ignored?
>
> CMake Warning at projects/libcxx/cmake/Modules/CheckLibcxxAtomic.cmake:49
> (message):
>   Host compiler must support std::atomic!
> Call Stack (most recent call first):
>   projects/libcxx/cmake/config-ix.cmake:63 (include)
>   projects/libcxx/CMakeLists.txt:476 (include)
>
> It's also showing up in the upstream bots:
>
> http://lab.llvm.org:8011/builders/libcxx-libcxxabi-x86_64-linux-debian/builds/1189/steps/cmake/logs/stdio
>
> The linker errors (in my cmake) are actually:
> CMakeFiles/cmTC_354e0.dir/src.cxx.o: In function `__clang_call_terminate':
> src.cxx:(.text.__clang_call_terminate[__clang_call_terminate]+0x2):
> undefined reference to `__cxa_begin_catch'
> src.cxx:(.text.__clang_call_terminate[__clang_call_terminate]+0xb):
> undefined reference to `std::terminate()'
> CMakeFiles/cmTC_354e0.dir/src.cxx.o:(.data.DW.ref.__gxx_personality_v0[DW.ref.__gxx_personality_v0]+0x0):
> undefined reference to `__gxx_personality_v0'
> clang-8: error: linker command failed with exit code 1 (use -v to see
> invocation)
> CMakeFiles/cmTC_354e0.dir/build.make:97: recipe for target 'cmTC_354e0'
> failed
>
> --
> Krzysztof Parzyszek  kparzysz at quicinc.com   LLVM compiler development
>
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> cfe-dev at lists.llvm.org
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