diff options
Diffstat (limited to 'config/tls.m4')
| -rw-r--r-- | config/tls.m4 | 11 |
1 files changed, 8 insertions, 3 deletions
diff --git a/config/tls.m4 b/config/tls.m4 index ef7e6d0b55..4e170c8d6a 100644 --- a/config/tls.m4 +++ b/config/tls.m4 @@ -38,11 +38,16 @@ AC_DEFUN([GCC_CHECK_TLS], [ CFLAGS="$chktls_save_CFLAGS" if test "X$thread_CFLAGS" != Xfailed; then CFLAGS="$thread_CFLAGS $chktls_save_CFLAGS" + dnl Test for an old glibc bug that violated the __thread property. + dnl Use volatile to ensure the compiler won't optimize away pointer + dnl accesses it might otherwise assume to be redundant, or reorder + dnl them and reuse storage, which might lead to them pointing to + dnl the same location. AC_RUN_IFELSE( [AC_LANG_PROGRAM( [#include <pthread.h> __thread int a; - static int *a_in_other_thread; + static int *volatile a_in_other_thread; static void * thread_func (void *arg) { @@ -51,11 +56,11 @@ AC_DEFUN([GCC_CHECK_TLS], [ }], [pthread_t thread; void *thread_retval; - int *a_in_main_thread; + int *volatile a_in_main_thread; + a_in_main_thread = &a; if (pthread_create (&thread, (pthread_attr_t *)0, thread_func, (void *)0)) return 0; - a_in_main_thread = &a; if (pthread_join (thread, &thread_retval)) return 0; return (a_in_other_thread == a_in_main_thread);])], |