Re: Gthreads patch to disable static initializer macros

[Jack Howarth <howarth at bromo dot med dot uc dot edu>]

On Sun, Feb 05, 2012 at 08:26:22PM +0000, Jonathan Wakely wrote:
> PRs libstdc++/51296 and libstdc++/51906 are both caused by problems
> with the Pthreads static initializer macros such as
> PTHREAD_MUTEX_INITIALIZER.
> 
> On Tru64 PTHREAD_MUTEX_INITIALIZER and PTHREAD_COND_INITIALIZER can
> only be used for statically-initialized variables, as allowed by POSIX
> currently, but http://austingroupbugs.net/view.php?id=70#c127 removes
> that limitation for the next POSIX standard. C++11 needs to use those
> macros for variables with automatic and dynamic scope, because the
> init functions can't be used in constexpr constructors.
> 
> On Mac OS X 10.7 the PTHREAD_RECURSIVE_MUTEX_INITIALIZER is buggy.
> This has shown up now because C++11 threads weren't enabled on darwin
> before 4.7
> 
> My suggestion is to modify gthr-posix.h with the attached patch, so
> that target maintainers can define e.g.
> _GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC to force use of the init
> function instead of the __GTHREAD_RECURSIVE_MUTEX_INIT initializer.
> The patch includes a change to do that for darwin.
> 
> This has been testing on darwin, if Rainer tests it successfully on
> Tru64 will the gthr-posix.h change be acceptable?

There are no unexpected libstdc++ testsuite regressions on x86_64-apple-darwin11 with this
patch applied to current gcc trunk.


> diff --git a/libgcc/gthr-posix.h b/libgcc/gthr-posix.h
> index 46054f6..45b15a8 100644
> --- a/libgcc/gthr-posix.h
> +++ b/libgcc/gthr-posix.h
> @@ -74,6 +74,20 @@ typedef struct timespec __gthread_time_t;
>  #define __GTHREAD_COND_INIT PTHREAD_COND_INITIALIZER
>  #define __GTHREAD_TIME_INIT {0,0}
>  
> +#ifdef _GTHREAD_USE_MUTEX_INIT_FUNC
> +# undef __GTHREAD_MUTEX_INIT
> +# define __GTHREAD_MUTEX_INIT_FUNCTION __gthread_mutex_init_function
> +#endif
> +#ifdef _GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC
> +# undef __GTHREAD_RECURSIVE_MUTEX_INIT
> +# undef __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION
> +# define __GTHREAD_RECURSIVE_MUTEX_INIT_FUNCTION __gthread_recursive_mutex_init_function
> +#endif
> +#ifdef _GTHREAD_USE_COND_INIT_FUNC
> +# undef __GTHREAD_COND_INIT
> +# define __GTHREAD_COND_INIT_FUNCTION __gthread_cond_init_function
> +#endif
> +
>  #if SUPPORTS_WEAK && GTHREAD_USE_WEAK
>  # ifndef __gthrw_pragma
>  #  define __gthrw_pragma(pragma)
> @@ -730,6 +744,15 @@ __gthread_setspecific (__gthread_key_t __key, const void *__ptr)
>    return __gthrw_(pthread_setspecific) (__key, __ptr);
>  }
>  
> +#ifdef _GTHREAD_USE_MUTEX_INIT_FUNC
> +static inline void
> +__gthread_mutex_init_function (__gthread_mutex_t *__mutex)
> +{
> +  if (__gthread_active_p ())
> +    __gthrw_(pthread_mutex_init) (__mutex, NULL);
> +}
> +#endif
> +
>  static inline int
>  __gthread_mutex_destroy (__gthread_mutex_t *__mutex)
>  {
> @@ -778,7 +801,8 @@ __gthread_mutex_unlock (__gthread_mutex_t *__mutex)
>      return 0;
>  }
>  
> -#ifndef PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP
> +#if !defined( PTHREAD_RECURSIVE_MUTEX_INITIALIZER_NP) \
> +  || defined(_GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC)
>  static inline int
>  __gthread_recursive_mutex_init_function (__gthread_recursive_mutex_t *__mutex)
>  {
> @@ -828,6 +852,15 @@ __gthread_recursive_mutex_unlock (__gthread_recursive_mutex_t *__mutex)
>    return __gthread_mutex_unlock (__mutex);
>  }
>  
> +#ifdef _GTHREAD_USE_COND_INIT_FUNC
> +static inline void
> +__gthread_cond_init_function (__gthread_cond_t *__cond)
> +{
> +  if (__gthread_active_p ())
> +    __gthrw_(pthread_cond_init) (__cond, NULL);
> +}
> +#endif
> +
>  static inline int
>  __gthread_cond_broadcast (__gthread_cond_t *__cond)
>  {
> diff --git a/libstdc++-v3/config/os/bsd/darwin/os_defines.h b/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> index ccefeaf..421478d 100644
> --- a/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> +++ b/libstdc++-v3/config/os/bsd/darwin/os_defines.h
> @@ -39,4 +39,7 @@
>  // -flat_namespace to work around the way that it doesn't.
>  #define _GLIBCXX_WEAK_DEFINITION __attribute__ ((weak))
>  
> +// Static initializer macro is buggy in darwin, see libstdc++/51906
> +#define _GTHREAD_USE_RECURSIVE_MUTEX_INIT_FUNC
> +
>  #endif