c-common.c (check_format_info): Warn for non-constant format strings with…

c-common.c (check_format_info): Warn for non-constant format strings with strftime formats if -Wformat-nonliteral.

	* c-common.c (check_format_info): Warn for non-constant format
	strings with strftime formats if -Wformat-nonliteral.  Where the
	format can convert arguments, if the format is not a string
	literal and there are no arguments to the format, give a different
	warning message from the general non-string-literal case.

testsuite:
	* gcc.dg/format-nonlit-3.c: New test.

From-SVN: r38105

gcc/ChangeLog

 2000-12-07  Joseph S. Myers  <jsm28@cam.ac.uk>
 
+	* c-common.c (check_format_info): Warn for non-constant format
+	strings with strftime formats if -Wformat-nonliteral.  Where the
+	format can convert arguments, if the format is not a string
+	literal and there are no arguments to the format, give a different
+	warning message from the general non-string-literal case.
+
+2000-12-07  Joseph S. Myers  <jsm28@cam.ac.uk>
+
 	* c-common.c (format_wanted_type): Add reading_from_flag.
 	(print_char_table): Mark %s and %S formats with flag "R".
 	(check_format_info_main): Set up reading_from_flag appropriately.

gcc/c-common.c

@@ -2345,9 +2345,30 @@ check_format_info (status, info, params)
       /* Functions taking a va_list normally pass a non-literal format
 	 string.  These functions typically are declared with
 	 first_arg_num == 0, so avoid warning in those cases.  */
-      if (info->first_arg_num != 0 && warn_format_nonliteral)
+      if (!(format_types[info->format_type].flags & FMT_FLAG_ARG_CONVERT))
+	{
+	  /* For strftime-like formats, warn for not checking the format
+	     string; but there are no arguments to check.  */
+	  if (warn_format_nonliteral)
+	    status_warning (status, "format not a string literal, format string not checked");
+	}
+      else if (info->first_arg_num != 0)
+	{
+	  /* If there are no arguments for the format at all, we may have
+	     printf (foo) which is likely to be a security hole.  */
+	  while (arg_num + 1 < info->first_arg_num)
+	    {
+	      if (params == 0)
+		break;
+	      params = TREE_CHAIN (params);
+	      ++arg_num;
+	    }
+	  if (params == 0 && warn_format_nonliteral)
+	    status_warning (status, "format not a string literal and no format arguments");
+	  else if (warn_format_nonliteral)
 	    status_warning (status, "format not a string literal, argument types not checked");
 	}
+    }
 
   /* If there were extra arguments to the format, normally warn.  However,
      the standard does say extra arguments are ignored, so in the specific

gcc/testsuite/ChangeLog

 2000-12-07  Joseph S. Myers  <jsm28@cam.ac.uk>
 
+	* gcc.dg/format-nonlit-3.c: New test.
+
+2000-12-07  Joseph S. Myers  <jsm28@cam.ac.uk>
+
 	* gcc.dg/c90-printf-1.c: Add test for printf formats reading
 	through a null pointer.
 

gcc/testsuite/gcc.dg/format-nonlit-3.c

+/* Test for warnings for non-string-literal formats.  Test for strftime formats.  */
+/* Origin: Joseph Myers <jsm28@cam.ac.uk> */
+/* { dg-do compile } */
+/* { dg-options "-std=gnu99 -Wformat -Wformat-nonliteral" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+struct tm;
+
+extern size_t strftime (char *, size_t, const char *, const struct tm *);
+
+void
+foo (char *s, size_t m, const struct tm *tp, char *fmt)
+{
+  strftime (s, m, fmt, tp); /* { dg-warning "format string" "non-literal" } */
+}