update NEWS.stable

[gnulib.git] / m4 / extensions.m4

diff --git a/m4/extensions.m4 b/m4/extensions.m4
index 611fcfd..22156e0 100644 (file)
--- a/m4/extensions.m4
+++ b/m4/extensions.m4
@@ -1,7 +1,7 @@
-# serial 6  -*- Autoconf -*-
+# serial 10  -*- Autoconf -*-
 # Enable extensions on systems that normally disable them.
 
-# Copyright (C) 2003, 2006-2008 Free Software Foundation, Inc.
+# Copyright (C) 2003, 2006-2011 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.
@@ -12,6 +12,20 @@
 # enough in this area it's likely we'll need to redefine
 # AC_USE_SYSTEM_EXTENSIONS for quite some time.
 
+# If autoconf reports a warning
+#     warning: AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
+# or  warning: AC_RUN_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS
+# the fix is
+#   1) to ensure that AC_USE_SYSTEM_EXTENSIONS is never directly invoked
+#      but always AC_REQUIREd,
+#   2) to ensure that for each occurrence of
+#        AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+#      or
+#        AC_REQUIRE([gl_USE_SYSTEM_EXTENSIONS])
+#      the corresponding gnulib module description has 'extensions' among
+#      its dependencies. This will ensure that the gl_USE_SYSTEM_EXTENSIONS
+#      invocation occurs in gl_EARLY, not in gl_INIT.
+
 # AC_USE_SYSTEM_EXTENSIONS
 # ------------------------
 # Enable extensions on systems that normally disable them,
@@ -20,7 +34,7 @@
 # AC_DEFINE.  The goal here is to define all known feature-enabling
 # macros, then, if reports of conflicts are made, disable macros that
 # cause problems on some platforms (such as __EXTENSIONS__).
-AC_DEFUN([AC_USE_SYSTEM_EXTENSIONS],
+AC_DEFUN_ONCE([AC_USE_SYSTEM_EXTENSIONS],
 [AC_BEFORE([$0], [AC_COMPILE_IFELSE])dnl
 AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
 
@@ -53,6 +67,10 @@ AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
 #ifndef _ALL_SOURCE
 # undef _ALL_SOURCE
 #endif
+/* Enable general extensions on MacOS X.  */
+#ifndef _DARWIN_C_SOURCE
+# undef _DARWIN_C_SOURCE
+#endif
 /* Enable GNU extensions on systems that have them.  */
 #ifndef _GNU_SOURCE
 # undef _GNU_SOURCE
@@ -74,13 +92,14 @@ AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
     [ac_cv_safe_to_define___extensions__],
     [AC_COMPILE_IFELSE(
        [AC_LANG_PROGRAM([[
-#        define __EXTENSIONS__ 1
-         ]AC_INCLUDES_DEFAULT])],
+#         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([_ALL_SOURCE])
+  AC_DEFINE([_DARWIN_C_SOURCE])
   AC_DEFINE([_GNU_SOURCE])
   AC_DEFINE([_POSIX_PTHREAD_SEMANTICS])
   AC_DEFINE([_TANDEM_SOURCE])
@@ -90,5 +109,15 @@ AC_BEFORE([$0], [AC_RUN_IFELSE])dnl
 # ------------------------
 # Enable extensions on systems that normally disable them,
 # typically due to standards-conformance issues.
-AC_DEFUN([gl_USE_SYSTEM_EXTENSIONS],
-  [AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])])
+AC_DEFUN_ONCE([gl_USE_SYSTEM_EXTENSIONS],
+[
+  dnl Require this macro before AC_USE_SYSTEM_EXTENSIONS.
+  dnl gnulib does not need it. But if it gets required by third-party macros
+  dnl after AC_USE_SYSTEM_EXTENSIONS is required, autoconf 2.62..2.63 emit a
+  dnl warning: "AC_COMPILE_IFELSE was called before AC_USE_SYSTEM_EXTENSIONS".
+  dnl Note: We can do this only for one of the macros AC_AIX, AC_GNU_SOURCE,
+  dnl AC_MINIX. If people still use AC_AIX or AC_MINIX, they are out of luck.
+  AC_REQUIRE([AC_GNU_SOURCE])
+
+  AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS])
+])