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explain NULL casts

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This commit is contained in:
christos 2011-09-01 09:33:01 +00:00
parent c20851872a
commit d98d733735
1 changed files with 12 additions and 2 deletions
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14
share/misc/style
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@ -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 @@ function(int a1, int a2, float fl, int a4)
* 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)".
*