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

[JF Bastien via cfe-dev]

> On Mar 27, 2019, at 12:59 PM, Brian M. Rzycki via cfe-dev <cfe-dev at lists.llvm.org> wrote:
> 
> 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 <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!”

This change?
https://github.com/llvm/llvm-project/commit/81dbc02671b223 <https://github.com/llvm/llvm-project/commit/81dbc02671b223>
It’s an LLDB commit, doesn’t seem related. Maybe an adjacent change was the root cause?


> On Wed, Mar 27, 2019 at 1:20 PM Krzysztof Parzyszek via cfe-dev <cfe-dev at lists.llvm.org <mailto: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 <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 <mailto:kparzysz at quicinc.com>   LLVM compiler development
> 
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