X-Git-Url: https://git.saurik.com/bison.git/blobdiff_plain/77373efad24be4ed77391c9e8ab2f85285810311..ef51bfa744db744dc4b2eff1ba9d6334c807f8e6:/data/c.m4

diff --git a/data/c.m4 b/data/c.m4
index 33b1d4b0..195c441d 100644
--- a/data/c.m4
+++ b/data/c.m4
@@ -1,8 +1,8 @@
                                                             -*- Autoconf -*-
 
 # C M4 Macros for Bison.
-# Copyright (C) 2002, 2004, 2005, 2006, 2007, 2008, 2009 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
@@ -138,23 +138,39 @@ m4_define([b4_int_type_for],
 # --------------------------------------------
 # Without inducing a comparison warning from the compiler, check if the
 # literal value LITERAL equals VALUE from table TABLE, which must have
-# TABLE_min and TABLE_max defined.
+# TABLE_min and TABLE_max defined.  YYID must be defined as an identity
+# function that suppresses warnings about constant conditions.
 m4_define([b4_table_value_equals],
 [m4_if(m4_eval($3 < m4_indir([b4_]$1[_min])
                || m4_indir([b4_]$1[_max]) < $3), [1],
        [[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])