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.

3 files changed, 46 insertions, 23 deletions

diff --git a/contrib/gcc/c-common.c b/contrib/gcc/c-common.c
index 78b4d858acbf..eace598e1ae0 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)
diff --git a/contrib/gcc/c-tree.h b/contrib/gcc/c-tree.h
index 02f57c3b9dca..5d132d0a0d2f 100644
--- a/contrib/gcc/c-tree.h
+++ b/contrib/gcc/c-tree.h
@@ -159,7 +159,7 @@ extern void gen_aux_info_record                 PROTO((tree, int, int, int));
 extern void declare_function_name               PROTO((void));
 extern void decl_attributes                     PROTO((tree, tree, tree));
 extern void init_function_format_info		PROTO((void));
-extern void record_function_format		PROTO((tree, tree, int, int, int));
+extern void record_function_format		PROTO((tree, tree, int, int, int, int));
 extern void check_function_format		PROTO((tree, tree, tree));
 /* Print an error message for invalid operands to arith operation CODE.
    NOP_EXPR is used as a special case (see truthvalue_conversion).  */
diff --git a/contrib/gcc/extend.texi b/contrib/gcc/extend.texi
index e85799c610d5..8eee0305664b 100644
--- a/contrib/gcc/extend.texi
+++ b/contrib/gcc/extend.texi
@@ -1394,13 +1394,15 @@ for consistency with the @code{printf} style format string argument
 @code{my_format}.
 
 The parameter @var{archetype} determines how the format string is
-interpreted, and should be either @code{printf} or @code{scanf}.  The
-parameter @var{string-index} specifies which argument is the format
-string argument (starting from 1), while @var{first-to-check} is the
-number of the first argument to check against the format string.  For
-functions where the arguments are not available to be checked (such as
-@code{vprintf}), specify the third parameter as zero.  In this case the
-compiler only checks the format string for consistency.
+interpreted, and should be @code{printf}, @code{printf0}, or
+@code{scanf}.  @code{printf0} allows the format string to be a null
+pointer, while @code{printf} does not.  The parameter @var{string-index}
+specifies which argument is the format string argument (starting
+from 1), while @var{first-to-check} is the number of the first
+argument to check against the format string.  For functions where
+the arguments are not available to be checked (such as @code{vprintf}),
+specify the third parameter as zero.  In this case the compiler
+only checks the format string for consistency.
 
 In the example above, the format string (@code{my_format}) is the second
 argument of the function @code{my_print}, and the arguments to check