Module Name: src
Committed By: christos
Date: Thu Sep 1 09:33:02 UTC 2011
Modified Files:
src/share/misc: style
Log Message:
explain NULL casts
To generate a diff of this commit:
cvs rdiff -u -r1.48 -r1.49 src/share/misc/style
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/share/misc/style
diff -u src/share/misc/style:1.48 src/share/misc/style:1.49
--- src/share/misc/style:1.48 Sat Aug 27 13:48:11 2011
+++ src/share/misc/style Thu Sep 1 05:33:01 2011
@@ -1,4 +1,4 @@
-/* $NetBSD: style,v 1.48 2011/08/27 17:48:11 joerg Exp $ */
+/* $NetBSD: style,v 1.49 2011/09/01 09:33:01 christos Exp $ */
/*
* The revision control tag appears first, with a blank line after it.
@@ -30,7 +30,7 @@
#include <sys/cdefs.h>
__COPYRIGHT("@(#) Copyright (c) 2008\
The NetBSD Foundation, inc. All rights reserved.");
-__RCSID("$NetBSD: style,v 1.48 2011/08/27 17:48:11 joerg Exp $");
+__RCSID("$NetBSD: style,v 1.49 2011/09/01 09:33:01 christos Exp $");
/*
* VERY important single-line comments look like this.
@@ -354,6 +354,16 @@
* not:
* !(p = f())
*
+ * The notable exception here is varyadic functions. Since our
+ * code is designed to compile and work on different environments
+ * where we don't have control over the NULL definition (on NetBSD
+ * it is defined as ((void *)0), but on other systems it can be
+ * defined as (0) and both definitions are valid under ANSI C), it
+ * it advised to cast NULL to a pointer on varyadic functions,
+ * because on machines where sizeof(pointer) != sizeof(int) and in
+ * the absence of a prototype in scope, passing an un-casted NULL,
+ * will result in passing an int on the stack instead of a pointer.
+ *
* Don't use `!' for tests unless it's a boolean.
* E.g. use "if (*p == '\0')", not "if (!*p)".
*
