From 69375a37dead5fb85418ed6f652902a3d310bf2f Mon Sep 17 00:00:00 2001
From: Richard Kenner <kenner@gcc.gnu.org>
Date: Sun, 13 Apr 1997 12:49:45 -0400
Subject: [PATCH] cexp.y (warn_undef): New variable.

(exp): Optionally warn about undefined identifiers that evaluate to 0.

From-SVN: r13877
---
 gcc/cexp.y | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/gcc/cexp.y b/gcc/cexp.y
index 2d2d34f8b28..133539f6c5d 100644
--- a/gcc/cexp.y
+++ b/gcc/cexp.y
@@ -164,6 +164,9 @@ extern int traditional;
 /* Flag for -lang-c89.  */
 extern int c89;
 
+/* Flag for -Wundef.  */
+extern int warn_undef;
+
 #ifndef CHAR_TYPE_SIZE
 #define CHAR_TYPE_SIZE BITS_PER_UNIT
 #endif
@@ -445,7 +448,10 @@ exp	:	exp '*' exp
 	|	CHAR
 			{ $$ = yylval.integer; }
 	|	NAME
-			{ $$.value = 0;
+			{ if (warn_undef && !skip_evaluation)
+			    warning ("`%.*s' is not defined",
+				     $1.length, $1.address);
+			  $$.value = 0;
 			  $$.signedp = SIGNED; }
 	;
 
-- 
2.30.2