[Buildroot] [PATCH] gamin: improve PTHREAD_MUTEX_RECURSIVE_NP patch to fix build issue

[Thomas Petazzoni <thomas.petazzoni@free-electrons.com>]

Hello,

On Wed, 20 Jul 2016 21:47:11 +0200, Thomas Petazzoni wrote:
> In the gamin package, patch
> 0003-fix-missing-PTHREAD_MUTEX_RECURSIVE_NP.patch was introduced to fix
> the build with musl. Indeed, while musl defines "linux", it does not
> define PTHREAD_MUTEX_RECURSIVE_NP, but only PTHREAD_MUTEX_RECURSIVE. So
> the check was simplified to only verify if PTHREAD_MUTEX_RECURSIVE_NP is
> defined.
> 
> However, this doesn't work well with uClibc linuxthreads. In uClibc,
> PTHREAD_MUTEX_RECURSIVE_NP and PTHREAD_MUTEX_RECURSIVE are not
> pre-processor defines, but enum values. For this reason, even if
> PTHREAD_MUTEX_RECURSIVE_NP actually exists, #if
> defined(PTHREAD_MUTEX_RECURSIVE_NP) is false. So, the gamin code falls
> back to using PTHREAD_MUTEX_RECURSIVE.
> 
> Except that for uClibc linuxthreads, PTHREAD_MUTEX_RECURSIVE is defined
> only if __USE_UNIX98 is defined. For the NPTL implementation,
> PTHREAD_MUTEX_RECURSIVE is defined either if __USE_UNIX98 or
> __USE_XOPEN2K8 are defined. This strange difference has been reported to
> uClibc-ng upstream [1].
> 
> However, regardless of this uClibc behavior, using #if defined to check
> for the availability of PTHREAD_MUTEX_RECURSIVE_NP is not good. This
> commit therefore switches to using a proper AC_CHECK_DECL() autoconf
> test, which works regardless of whether the value is #define'd or
> defined as an enum value.
> 
> This fixes the build of gamin on linuxthreads platforms, such as
> Microblaze or m68k.
> 
> Fixes:
> 
>   http://autobuild.buildroot.net/results/887df97196d7777efbf18a7bee91aa45c1a98700/ (Microblaze)
>   http://autobuild.buildroot.net/results/eb4389474e1b30b5c395a07a857da13a66763bdb/ (m68k)
> 
> [1] http://mailman.uclibc-ng.org/pipermail/devel/2016-July/001087.html
> 
> Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
> ---
>  ...03-fix-missing-PTHREAD_MUTEX_RECURSIVE_NP.patch | 31 +++++++++++++++++-----
>  1 file changed, 25 insertions(+), 6 deletions(-)

Applied to master.

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com