X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Fextensions.m4;h=1330503f0d77cf417f4e1e54062f258246401afb;hb=50933cccef270ca1f2d948700913830dba0b9a06;hp=99fba9f63bc63c1a2747964fcc4fa51649edf6c2;hpb=441aa3044f43e5572f58c354f01e6bc070acd5c7;p=gnulib.git

diff --git a/m4/extensions.m4 b/m4/extensions.m4
index 99fba9f63..1330503f0 100644
--- a/m4/extensions.m4
+++ b/m4/extensions.m4
@@ -1,7 +1,7 @@
-# serial 8  -*- Autoconf -*-
+# serial 9  -*- Autoconf -*-
 # Enable extensions on systems that normally disable them.
 
-# Copyright (C) 2003, 2006-2009 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,