Subject: Re: no pthread_spinlock_t on Mac OS 10.6.4

From: "Gary V. Vaughan" <[email-masked]>
Date: Mon, 20 Sep 2010 14:14:46 +0700

Hi Paul,

Thanks for looking at this.

On 20 Sep 2010, at 13:21, Paul Eggert wrote:
> On 09/19/2010 07:43 PM, Gary V. Vaughan wrote:
>> my system headers have no pthread_spinlock_t definition, but
>> gnulib sees /usr/include/pthread.h and uses that instead of generating it's own,
>> ...
>> I don't know enough about pthreads to tell whether gnulib should paper over
>> the lack of spinlocks on Mac OS, or whether coreutils should be more careful
>> about using spinlocks without having tested for them first...
> 
> If MacOS doesn't have spinlocks, then from coreutils' point of view MacOS
> doesn't have proper thread support.  The simplest fix is for coreutils
> to use the substitute pthread.h on MacOS.  Does the following patch
> work for you?

It fixes the original spinlocks error I reported, but then the build falls over on lib/glthread/lock.c:

In file included from ../../lib/glthread/lock.h:93,
                 from ../../lib/glthread/lock.c:26:
./pthread.h:184: error: expected ')' before '*' token
./pthread.h:191: error: expected ')' before '*' token
./pthread.h:198: error: expected ')' before '*' token
./pthread.h:206: error: expected ')' before '*' token
../../lib/glthread/lock.c: In function 'glthread_recursive_lock_init_multithreaded':
../../lib/glthread/lock.c:321: warning: implicit declaration of function 'pthread_mutexattr_init'
../../lib/glthread/lock.c:324: warning: implicit declaration of function 'pthread_mutexattr_settype'
../../lib/glthread/lock.c:327: warning: implicit declaration of function 'pthread_mutexattr_destroy'

where lines 184, 191, 198 and 206 of lib/pthread.h each contain a use of pthread_spinlock_t.

lib/pthread.h does have a typedef for pthread_spinlock_t, but it is predicated on not having HAVE_PTHREAD_T defined (which I do):

  ; sed -n /HAVE_PTHREAD_T/,/endif/p lib/pthread.h 
  #ifndef HAVE_PTHREAD_T
   typedef int pthread_t;
   typedef int pthread_attr_t;
   typedef int pthread_barrier_t;
   typedef int pthread_barrierattr_t;
   typedef int pthread_cond_t;
   typedef int pthread_condattr_t;
   typedef int pthread_key_t;
   typedef int pthread_mutex_t;
   typedef int pthread_mutexattr_t;
   typedef int pthread_once_t;
   typedef int pthread_rwlock_t;
   typedef int pthread_rwlockattr_t;
   typedef int pthread_spinlock_t;
  #endif
  ; grep HAVE_PTHREAD_T lib/config.h
  #define HAVE_PTHREAD_T 1

> diff --git a/m4/pthread.m4 b/m4/pthread.m4
> index 69866cb..121d84d 100644
> --- a/m4/pthread.m4
> +++ b/m4/pthread.m4
> @@ -6,19 +6,22 @@ dnl with or without modifications, as long as this notice is preserved.
> 
> AC_DEFUN([gl_PTHREAD_CHECK],
>   [AC_CHECK_HEADERS_ONCE([pthread.h])
> +   AC_CHECK_TYPES([pthread_t])
> 
>    LIB_PTHREAD=
> -   PTHREAD_H=
> -   if test "$ac_cv_header_pthread_h" = yes; then
> -     gl_saved_libs=$LIBS
> -     AC_SEARCH_LIBS([pthread_create], [pthread],
> -       [if test "$ac_cv_search_pthread_create" != "none required"; then
> -          LIB_PTHREAD="$ac_cv_search_pthread_create"
> -        fi])
> -     LIBS="$gl_saved_libs"
> -   else
> -     AC_CHECK_TYPES([pthread_t])
> -     PTHREAD_H='pthread.h'
> +   PTHREAD_H='pthread.h'
> +   if test "$ac_cv_header_pthread_h" = yes &&
> +      test "$ac_cv_type_pthread_t" = yes; then
> +     AC_CHECK_TYPE([pthread_spinlock_t])
> +     if test "$ac_cv_type_pthread_spinlock_t" = yes; then
> +       PTHREAD_H=
> +       gl_saved_libs=$LIBS
> +       AC_SEARCH_LIBS([pthread_create], [pthread],
> +         [if test "$ac_cv_search_pthread_create" != "none required"; then
> +            LIB_PTHREAD="$ac_cv_search_pthread_create"
> +          fi])
> +       LIBS="$gl_saved_libs"
> +     fi
>    fi
> 
>    AC_SUBST([LIB_PTHREAD])

Cheers,
-- 
Gary V. Vaughan ([email-masked])