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Date: Sun, 26 Nov 2000 22:20:48 -0800
From: Kris Kennaway <kris@FreeBSD.org>
To: audit@FreeBSD.org
Subject: gcc __attributes for format strings
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Okay, looks like we can play with some gcc attributes to flag things
as format strings. For example:

Index: create_chunk.c
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=
=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D
RCS file: /mnt/ncvs/src/lib/libdisk/create_chunk.c,v
retrieving revision 1.54
diff -u -r1.54 create_chunk.c
--- create_chunk.c	2000/11/06 23:15:01	1.54
+++ create_chunk.c	2000/11/27 06:14:00
@@ -28,6 +28,8 @@
 #include <pwd.h>
 #include "libdisk.h"
=20
+static void msgDebug(char *, ...) __printf0like(1,0);
+
 /* Clone these two from sysinstall because we need our own copies
  * due to link order problems with `crunch'.  Feh!
  */

__printf0like(a,b) says "treat argument 'a' as a printf format string
which may be null, and arguments starting with 'b' are the arguments
to the format string". b=3D0 is for the case of a varargs function like
above.

__printflike(a,b) is the same thing except it doesn't allow a NULL
format string.

We need to go through and prototype functions appropriately (in
headers, or internally) - I think it's possible to fix all of the
-Wnon-const-format warnings this way.

The docs in contrib/gcc/extend.texi explain this better - can someone
check that I'm doing the right thing?

Kris

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