-*- Autoconf -*-
# C M4 Macros for Bison.
-# Copyright (C) 2002, 2004-2010 Free Software Foundation, Inc.
+
+# Copyright (C) 2002, 2004-2012 Free Software Foundation, Inc.
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
[[YYID (0)]],
[[((]$2[) == (]$3[))]])])
+
## ---------##
## Values. ##
## ---------##
-# b4_null
----------
-# Return a null pointer constant. NULL infringes on the user name
-# space in C, so use 0 rather than NULL.
-m4_define([b4_null], [0])
+# b4_null_define
+# --------------
+# Portability issues: define a YY_NULL appropriate for the current
+# language (C, C++98, or C++11).
+m4_define([b4_null_define],
+[# ifndef YY_NULL
+# if defined __cplusplus && 201103L <= __cplusplus
+# define YY_NULL nullptr
+# else
+# define YY_NULL 0
+# endif
+# endif[]dnl
+])
+
+
+# b4_null
+# -------
+# Return a null pointer constant.
+m4_define([b4_null], [YY_NULL])