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

Wed Mar 27 14:53:14 PDT 2019

I've bisected down the previously mentioned commit deltas to the following
commit. This is the first instance of the warning message.

https://github.com/llvm/llvm-project/commit/21450545d14

[libc++] decoupling Freestanding atomic<T> from libatomic.a

This patch introduces non-lockfree atomics that do not require using
an external libatomic. This work is done with the long-term goal of
allowing the use of <atomic> in freestanding environments.

Thanks to Olivier Giroux for the patch.
Differential Revision: https://reviews.llvm.org/D56913

llvm-svn: 355318

On Wed, Mar 27, 2019 at 3:43 PM Brian M. Rzycki <brzycki at gmail.com> wrote:

> Sorry, I wasn't clear. I meant the change is somewhere between those two
> commits: those are two nightly builds 24 hours apart.
>
> On Wed, Mar 27, 2019 at 3:08 PM JF Bastien <jfbastien at apple.com> wrote:
>
>>
>>
>> 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). 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
>>
>> 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> 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
>>>
>>> _______________________________________________
>>> cfe-dev mailing list
>>> cfe-dev at lists.llvm.org
>>> https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
>>>
>> _______________________________________________
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>>
>>
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