Re: clang 13 and __STDC_NO_ATOMICS__

On Nov 2, 2021, at 4:01 PM, Brad Smith <brad@comstyle.com> wrote:
>
> On 11/2/2021 2:41 PM, Kurt Miller wrote:
>
>> On Nov 1, 2021, at 10:20 PM, Brad Smith <brad@comstyle.com> wrote:
>>>
>>> On 10/28/2021 8:42 AM, Jeremie Courreges-Anglas wrote:
>>>> On Thu, Oct 28 2021, Jeremie Courreges-Anglas <jca@wxcvbn.org> wrote:
>>>>> On Thu, Oct 28 2021, Christian Weisgerber <naddy@mips.inka.de> wrote:
>>>>>> I ran an amd64 bulk build with base clang updated to LLVM 13.
>>>>>>
>>>>>> There is substantial fallout. Java appears to be broken and there
>>>>>> are numerous failures caused by clang 13 issuing new warnings and
>>>>>> ports using -Werror.
>>>>>>
>>>>>> Failure logs:
>>>>>> http://build-failures.rhaalovely.net/amd64-clang/2021-10-27/
>>>>>>
>>>>>> The final error may be misleading. For instance, devel/libdsm fails
>>>>>> with a linker error "undefined reference to pthread_create", but
>>>>>> the root cause is -Werror breaking a configure check.
>>>>>>
>>>>>> Below there's a list of affected ports. Several hundred more weren't
>>>>>> built because they depend on something that failed.
>>>>>>
>>>>>> audio/cmus
>>>>> jsg@ pointed out that this new clang defines __STDC_NO_ATOMICS__
>>>>> which is most likely wrong. This breaks at least cmus:
>>>>>
>>>>> http://build-failures.rhaalovely.net/amd64-clang/2021-10-27/audio/cmus.log
>>>> Brad, are you sure that this change is 100% correct?
>>>> https://github.com/llvm/llvm-project/commit/d8cd7806310c51af912a647a6ca46de62ff13214
>>>>
>>>> Should we drop the __STDC_NO_ATOMICS__ define?
>>> The atomics part was my misunderstanding and is wrong. I have reverted it upstream and will
>>> have it merged into 13.
>> Thanks for fixing that. Can you explain why __STDC_NO_THREADS__ was retained? I'm
>> assuming that's disabling std::thread and related thread support which also seems wrong.
>
> This is for C11 not C++11.
>
> "If the macro constant __STDC_NO_THREADS__(C11) is defined by the compiler, the
> header <threads.h> and all of the names listed here are not provided."
>
> https://en.cppreference.com/w/c/thread
>
> OpenBSD currently does not implement C11 threads, unlike relatively new FreeBSD,
> NetBSD, Solaris, AIX, glibc, musl.
>
> https://svnweb.freebsd.org/base/head/lib/libstdthreads/threads.h
> https://cvsweb.netbsd.org/bsdweb.cgi/src/lib/libpthread/threads.h

Thank you for the clarification. I see now I was confusing c++11 and c11.

-Kurt