Patch for c/1017 (-Wmissing-format-attribute)

[Joseph S. Myers]

This patch addresses c/1017 by making -Wmissing-format-attribute only
suggest adding a format attribute if there's a parameter to which to
add such an attribute.

Bootstrapped with no regressions on i686-pc-linux-gnu.  OK to commit?

gcc/ChangeLog:
2000-12-09  Joseph S. Myers  <jsm28@cam.ac.uk>

	* c-common.c (check_function_format): Don't suggest adding format
	attributes to functions with no parameter to which to add them.

gcc/testsuite/ChangeLog:
2000-12-09  Joseph S. Myers  <jsm28@cam.ac.uk>

	* gcc.dg/format-miss-2.c: New test.

--- c-common.c.orig	Thu Dec  7 13:04:29 2000
+++ c-common.c	Sat Dec  9 11:51:19 2000
@@ -2047,8 +2047,25 @@ check_function_format (status, name, ass
 		    && info2->format_type == info->format_type)
 		  break;
 	      if (info2 == NULL)
-		warning ("function might be possible candidate for `%s' format attribute",
-			 format_types[info->format_type].name);
+		{
+		  /* Check if the current function has a parameter to which
+		     the format attribute could be attached; if not, it
+		     can't be a candidate for a format attribute, despite
+		     the vprintf-like or vscanf-like call.  */
+		  tree args;
+		  for (args = DECL_ARGUMENTS (current_function_decl);
+		       args != 0;
+		       args = TREE_CHAIN (args))
+		    {
+		      if (TREE_CODE (TREE_TYPE (args)) == POINTER_TYPE
+			  && (TYPE_MAIN_VARIANT (TREE_TYPE (TREE_TYPE (args)))
+			      == char_type_node))
+			break;
+		    }
+		  if (args != 0)
+		    warning ("function might be possible candidate for `%s' format attribute",
+			     format_types[info->format_type].name);
+		}
 	    }
 	  break;
 	}
--- testsuite/gcc.dg/format-miss-2.c.orig	Fri Sep 11 11:31:59 1998
+++ testsuite/gcc.dg/format-miss-2.c	Sat Dec  9 11:56:12 2000
@@ -0,0 +1,18 @@
+/* Test for warnings for missing format attributes.  Don't warn if no
+   relevant parameters for a format attribute; see c/1017.  */
+/* Origin: Joseph Myers <jsm28@cam.ac.uk> */
+/* { dg-do compile } */
+/* { dg-options "-std=gnu99 -Wformat -Wmissing-format-attribute" } */
+
+#include <stdarg.h>
+
+extern int vprintf (const char *restrict, va_list);
+
+void
+foo (int i, ...)
+{
+  va_list ap;
+  va_start (ap, i);
+  vprintf ("Foo %s bar %s", ap); /* { dg-bogus "candidate" "bogus printf attribute warning" } */
+  va_end (ap);
+}

-- 
Joseph S. Myers
jsm28@cam.ac.uk