Add support for a new archetype "printf0" for the "format" function

attribute.  It is like the existing "printf" archetype, except that
it doesn't complain if the format string is a null pointer.  See
the node "Function Attributes" in the GCC info pages if you don't
know what this is all about.

This change will allow us to add format string checking for the
err(3) family of functions.

1 files changed, 36 insertions, 15 deletions

diff --git a/contrib/gcc/c-common.c b/contrib/gcc/c-common.c
index 78b4d85..eace598 100644
--- a/contrib/gcc/c-common.c
+++ b/contrib/gcc/c-common.c
@@ -536,6 +536,7 @@ decl_attributes (node, attributes, prefix_attributes)
 	    int format_num;
 	    int first_arg_num;
 	    int is_scan;
+	    int null_format_ok;
 	    tree argument;
 	    int arg_num;
 	
@@ -550,15 +551,30 @@ decl_attributes (node, attributes, prefix_attributes)
 		&& (!strcmp (IDENTIFIER_POINTER (format_type), "printf")
 		    || !strcmp (IDENTIFIER_POINTER (format_type),
 				"__printf__")))
-	      is_scan = 0;
+	      {
+		is_scan = 0;
+		null_format_ok = 0;
+	      }
+	    else if (TREE_CODE (format_type) == IDENTIFIER_NODE
+		     && (!strcmp (IDENTIFIER_POINTER (format_type), "printf0")
+			 || !strcmp (IDENTIFIER_POINTER (format_type),
+				     "__printf0__")))
+	      {
+		is_scan = 0;
+		null_format_ok = 1;
+	      }
 	    else if (TREE_CODE (format_type) == IDENTIFIER_NODE
 		     && (!strcmp (IDENTIFIER_POINTER (format_type), "scanf")
 			 || !strcmp (IDENTIFIER_POINTER (format_type),
 				     "__scanf__")))
-	      is_scan = 1;
+	      {
+		is_scan = 1;
+		null_format_ok = 0;
+	      }
 	    else
 	      {
-		error ("unrecognized format specifier for `%s'");
+		error_with_decl (decl,
+		         "unrecognized format specifier for `%s'");
 		continue;
 	      }
 
@@ -625,7 +641,8 @@ decl_attributes (node, attributes, prefix_attributes)
 
 	    record_function_format (DECL_NAME (decl),
 				    DECL_ASSEMBLER_NAME (decl),
-				    is_scan, format_num, first_arg_num);
+				    is_scan, null_format_ok, format_num,
+				    first_arg_num);
 	    break;
 	  }
 
@@ -730,6 +747,7 @@ typedef struct function_format_info {
   tree name;			/* identifier such as "printf" */
   tree assembler_name;		/* optional mangled identifier (for C++) */
   int is_scan;			/* TRUE if *scanf */
+  int null_format_ok;		/* TRUE if the format string may be NULL */
   int format_num;		/* number of format argument */
   int first_arg_num;		/* number of first arg (zero for varargs) */
 } function_format_info;
@@ -748,15 +766,15 @@ static void check_format_info PROTO((function_format_info *, tree));
 void
 init_function_format_info ()
 {
-  record_function_format (get_identifier ("printf"), NULL_TREE, 0, 1, 2);
-  record_function_format (get_identifier ("fprintf"), NULL_TREE, 0, 2, 3);
-  record_function_format (get_identifier ("sprintf"), NULL_TREE, 0, 2, 3);
-  record_function_format (get_identifier ("scanf"), NULL_TREE, 1, 1, 2);
-  record_function_format (get_identifier ("fscanf"), NULL_TREE, 1, 2, 3);
-  record_function_format (get_identifier ("sscanf"), NULL_TREE, 1, 2, 3);
-  record_function_format (get_identifier ("vprintf"), NULL_TREE, 0, 1, 0);
-  record_function_format (get_identifier ("vfprintf"), NULL_TREE, 0, 2, 0);
-  record_function_format (get_identifier ("vsprintf"), NULL_TREE, 0, 2, 0);
+  record_function_format (get_identifier ("printf"), NULL_TREE, 0, 0, 1, 2);
+  record_function_format (get_identifier ("fprintf"), NULL_TREE, 0, 0, 2, 3);
+  record_function_format (get_identifier ("sprintf"), NULL_TREE, 0, 0, 2, 3);
+  record_function_format (get_identifier ("scanf"), NULL_TREE, 1, 0, 1, 2);
+  record_function_format (get_identifier ("fscanf"), NULL_TREE, 1, 0, 2, 3);
+  record_function_format (get_identifier ("sscanf"), NULL_TREE, 1, 0, 2, 3);
+  record_function_format (get_identifier ("vprintf"), NULL_TREE, 0, 0, 1, 0);
+  record_function_format (get_identifier ("vfprintf"), NULL_TREE, 0, 0, 2, 0);
+  record_function_format (get_identifier ("vsprintf"), NULL_TREE, 0, 0, 2, 0);
 }
 
 /* Record information for argument format checking.  FUNCTION_IDENT is
@@ -769,11 +787,12 @@ init_function_format_info ()
    (e.g. for varargs such as vfprintf).  */
 
 void
-record_function_format (name, assembler_name, is_scan,
+record_function_format (name, assembler_name, is_scan, null_format_ok,
 			format_num, first_arg_num)
       tree name;
       tree assembler_name;
       int is_scan;
+      int null_format_ok;
       int format_num;
       int first_arg_num;
 {
@@ -797,6 +816,7 @@ record_function_format (name, assembler_name, is_scan,
     }
 
   info->is_scan = is_scan;
+  info->null_format_ok = null_format_ok;
   info->format_num = format_num;
   info->first_arg_num = first_arg_num;
 }
@@ -876,7 +896,8 @@ check_format_info (info, params)
     format_tree = TREE_OPERAND (format_tree, 0); /* strip coercion */
   if (integer_zerop (format_tree))
     {
-      warning ("null format string");
+      if (!info->null_format_ok)
+	warning ("null format string");
       return;
     }
   if (TREE_CODE (format_tree) != ADDR_EXPR)