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From: Jens Gustedt <jens.gustedt@loria.fr>
Newsgroups: comp.lang.c,comp.programming.threads
Subject: Re: Trivial C11 threads.h wrapper (public domain)
Date: Mon, 01 Oct 2012 08:26:30 +0200
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Am 01.10.2012 01:48, schrieb Eric Sosman:
> On 9/30/2012 6:44 PM, Jens Gustedt wrote:
>> [...]
>> Ah, thinking of it a bit more, it is actually not "(void)" which is
>> problematic but the fact that the function may result in errno being
>> set to a non-zero value. I'll replace by something like
>>
>> if (pthread_mutex_destroy(&P99_ENCP(p00_mtx))) errno = 0;
> 
>     This would be a very bad thing to do in an implementation
> that is supposed to imitate a Standard C library function.
> 
>     7.5p3: "The value of errno in the initial thread is zero
>     at program startup [...] but is never set to zero by any
>     library function. [...]"
> 

Right. The reason is that I thought that pthread_mutex_destroy could
set errno to some error value. But re-reading the manual page of that
I see that the error code is in the function return. So there is no
need to do that at all.

(Otherwise I would have had to capture errno before the call and to
restore it if the call to pthread_mutex_destroy failed. Expensive.)

Thanks

Jens