re PR c++/64629 (-Wformat-security warns with const char *const vars)

	PR c++/64629
	* c-format.c (check_format_arg): Call decl_constant_value.

From-SVN: r219964

gcc/c-family/ChangeLog

+2015-01-21  Jason Merrill  <jason@redhat.com>
+
+	PR c++/64629
+	* c-format.c (check_format_arg): Call decl_constant_value.
+
 2015-01-19  Martin Liska  <mliska@suse.cz>
 
 	* c-common.c (handle_noicf_attribute): New function.

gcc/c-family/c-format.c

@@ -1443,6 +1443,13 @@ check_format_arg (void *ctx, tree format_tree,
   tree array_init;
   alloc_pool fwt_pool;
 
+  if (TREE_CODE (format_tree) == VAR_DECL)
+    {
+      /* Pull out a constant value if the front end didn't.  */
+      format_tree = decl_constant_value (format_tree);
+      STRIP_NOPS (format_tree);
+    }
+
   if (integer_zerop (format_tree))
     {
       /* Skip to first argument to check, so we can see if this format

gcc/testsuite/g++.dg/warn/Wformat-1.C

+// PR c++/64629
+// { dg-options "-Wformat -Wformat-security" }
+
+extern void bar (int, const char *, ...) __attribute__((format (printf, 2, 3)));
+void
+foo (void)
+{
+  const char *const msg = "abc";
+  bar (1, msg);
+}