Tweak comment.

[gnulib.git] / m4 / extensions.m4

diff --git a/m4/extensions.m4 b/m4/extensions.m4
index e9b6b54..4976079 100644 (file)
--- a/m4/extensions.m4
+++ b/m4/extensions.m4
@@ -1,10 +1,13 @@
 # Enable extensions on systems that normally disable them.
 
-# Copyright (C) 2003, 2005 Free Software Foundation, Inc.
+# Copyright (C) 2003, 2006 Free Software Foundation, Inc.
 # This file is free software; the Free Software Foundation
 # gives unlimited permission to copy and/or distribute it,
 # with or without modifications, as long as this notice is preserved.
 
+# This file is only needed in autoconf <= 2.59.  Newer versions of autoconf
+# have a macro AC_USE_SYSTEM_EXTENSIONS with identical semantics.
+
 # gl_USE_SYSTEM_EXTENSIONS
 # ------------------------
 # Enable extensions on systems that normally disable them,
@@ -19,8 +22,21 @@ AC_DEFUN([gl_USE_SYSTEM_EXTENSIONS], [
 
   AH_VERBATIM([__EXTENSIONS__],
 [/* Enable extensions on Solaris.  */
-#ifdef __EXTENSIONS__
+#ifndef __EXTENSIONS__
 # undef __EXTENSIONS__
+#endif
+#ifndef _POSIX_PTHREAD_SEMANTICS
+# undef _POSIX_PTHREAD_SEMANTICS
 #endif])
-  AC_DEFINE([__EXTENSIONS__])
+  AC_CACHE_CHECK([whether it is safe to define __EXTENSIONS__],
+    [ac_cv_safe_to_define___extensions__],
+    [AC_COMPILE_IFELSE(
+       [AC_LANG_PROGRAM([
+         #define __EXTENSIONS__ 1
+         AC_INCLUDES_DEFAULT])],
+       [ac_cv_safe_to_define___extensions__=yes],
+       [ac_cv_safe_to_define___extensions__=no])])
+  test $ac_cv_safe_to_define___extensions__ = yes &&
+    AC_DEFINE([__EXTENSIONS__])
+  AC_DEFINE([_POSIX_PTHREAD_SEMANTICS])
 ])