pthread: define thread-safe macros on some platforms

* m4/pthread.m4 (gl_PTHREAD_CHECK): Define macros needed
for thread-safe operation on some platforms.

1 files changed, 14 insertions, 0 deletions

diff --git a/m4/pthread.m4 b/m4/pthread.m4
index 1ed0dd335e..44538bd941 100644
--- a/m4/pthread.m4
+++ b/m4/pthread.m4
@@ -88,6 +88,20 @@ AC_DEFUN([gl_PTHREAD_CHECK],
    fi
    AC_SUBST([LIB_PTHREAD])
 
+   dnl Some systems optimize for single-threaded programs by default, and
+   dnl need special flags to disable these optimizations. For example, the
+   dnl definition of 'errno' in <errno.h>.
+   case "$host_os" in
+     aix* | freebsd*)
+       AC_DEFINE([_THREAD_SAFE], 1,
+         [Define on some systems, to enable only thread-safe operations.])
+     ;;
+     osf* | solaris*)
+       AC_DEFINE([_REENTRANT], 1,
+         [Define on some systems, to enable only thread-safe operations.])
+     ;;
+   esac
+
    AC_REQUIRE([AC_C_RESTRICT])
 ])