-# 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.
# 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,