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Re: [PATCH] misc/tst-clone3: Fix waiting for exited thread.

On 11/02/2019 08:59, Florian Weimer wrote:
> * Stefan Liebler:
>> I've first tried to include atomic.h, but it failed building on
>> x86_64. Thus I'm using the c11 atomic load in the updated patch.
>> Okay to commit?
>> As information, I've observed those gcc errors on x86_64:
>> In file included from ../sysdeps/unix/sysv/linux/x86_64/sysdep.h:30,
>>                  from ../sysdeps/x86_64/nptl/tls.h:28,
>>                  from ../sysdeps/x86/atomic-machine.h:23,
>>                  from ../include/atomic.h:50,
>>                  from ../sysdeps/unix/sysv/linux/tst-clone3.c:29:
>> ../sysdeps/unix/sysv/linux/dl-sysdep.h: In function
>> ‘_dl_discover_osversion’:
>> ../sysdeps/unix/sysv/linux/dl-sysdep.h:31:42: error: expected
>> declaration specifiers before ‘attribute_hidden’
>>  extern int _dl_discover_osversion (void) attribute_hidden;
>>                                           ^~~~~~~~~~~~~~~~
> That's because the test isn't in tests-internal.
>> +    while ((__tid = __atomic_load_n (ctid_ptr, __ATOMIC_ACQUIRE)) != 0)	\
> Actually, that's not a C11 atomic construct, but I think it's okay to
> use that here.  (The C11 stuff lives in <stdatomic.h> and should be
> functionally equivalent.)
> Sorry, this is a pet peeve of mine.  We have three different atomic
> access facilities that people refer to as C11 atomics: Our own
> <atomic.h>, the GCC __atomic builtins, and <stdatomic.h>.
> I still think this contributes to cognitive load, and we should
> eliminate all but one (leaving us with new-style atomics and the old
> macros in <atomic.h>).  The GCC __atomic builtins have the best freely
> available documentation, so they are a natural candidate IMHO.

It really annoying that C11 standard is not freely available from ISO,
although the working draft is still open [1]. I don't have a strong
opinion, but since there is support in the language itself and they
are fully supported by the compiler I also don't see why not prefer it.


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