Re: [PATCH] nptl: Avoid using PTHREAD_MUTEX_DEFAULT in macro definition [BZ #25271]

[Adhemerval Zanella <adhemerval dot zanella at linaro dot org>]

On 27/01/2020 10:53, Florian Weimer wrote:
> Commit 1c3f9acf1f1f75faa7a28bf39af64afd ("nptl: Add struct_mutex.h")
> replaced a zero constant with the identifier PTHREAD_MUTEX_DEFAULT
> in the macro PTHREAD_MUTEX_INITIALIZER.  However, that constant
> is not available in ISO C11 mode:
> 
> In file included from /usr/include/bits/thread-shared-types.h:74,
>                  from /usr/include/bits/pthreadtypes.h:23,
>                  from /usr/include/pthread.h:26,
>                  from bug25271.c:1:
> bug25271.c:3:21: error: ‘PTHREAD_MUTEX_DEFAULT’ undeclared here (not in a function)
>     3 | pthread_mutex_t m = PTHREAD_MUTEX_INITIALIZER;
>       |                     ^~~~~~~~~~~~~~~~~~~~~~~~~
> 
> This commit change the constant to the equivalent
> PTHREAD_MUTEX_TIMED_NP, which is in the POSIX extension namespace
> and thus always available.
> 
> Tested on x86_64-linux-gnu and i686-linux-gnu.  Verified that a
> minimal example now builds in -std=c11 mode.

LGTM, although I think we should add some more extensive tests when
2.32 opens.

> 
> -----
>  sysdeps/nptl/pthread.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sysdeps/nptl/pthread.h b/sysdeps/nptl/pthread.h
> index 7825737840..44dd707896 100644
> --- a/sysdeps/nptl/pthread.h
> +++ b/sysdeps/nptl/pthread.h
> @@ -84,7 +84,7 @@ enum
>  
>  
>  #define PTHREAD_MUTEX_INITIALIZER \
> - { {  __PTHREAD_MUTEX_INITIALIZER (PTHREAD_MUTEX_DEFAULT) } }
> + { {  __PTHREAD_MUTEX_INITIALIZER (PTHREAD_MUTEX_TIMED_NP) } }

Maybe add a comment stating why PTHREAD_MUTEX_TIMED_NP is the correct
initializer here?

>  #ifdef __USE_GNU
>  # define PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP \
>   { {  __PTHREAD_MUTEX_INITIALIZER (PTHREAD_MUTEX_RECURSIVE_NP) } }
>