From: Al Viro <viro@ftp.linux.org.uk>
To: Bodo Eggert <7eggert@gmx.de>
Cc: Jan Engelhardt <jengelh@linux01.gwdg.de>,
David Miller <davem@davemloft.net>,
satyam.sharma@gmail.com, linux-kernel@vger.kernel.org
Subject: Re: double exclamation (!!) suckage in the kernel
Date: Sat, 26 May 2007 17:50:09 +0100 [thread overview]
Message-ID: <20070526165009.GT4095@ftp.linux.org.uk> (raw)
In-Reply-To: <E1HrzHL-0000s2-Pv@be1.lrz>
On Sat, May 26, 2007 at 06:38:07PM +0200, Bodo Eggert wrote:
> Not exactly, if(foo) is the same as if( (int) foo), which is not
> guaranteed to result in non-null values for non-null pointers.
RTFStandard.
> ISO 9899/1999 says: "Any pointer may be converted to an integer type. [...]
> The result need not be in the range of values of any integer type."
... and it sure as hell does *NOT* say that controlling expression of
if statement is converted to an integer type. For pointers of for anything
else. if (v) is the same as if (v != 0) [6.8.4.1p2], and if v is a pointer,
0 in that comparison becomes a null pointer constant [6.5.9p5].
next prev parent reply other threads:[~2007-05-26 16:50 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <8oOAk-4mP-3@gated-at.bofh.it>
[not found] ` <8oPmF-5Fb-21@gated-at.bofh.it>
[not found] ` <8p4OH-3N0-15@gated-at.bofh.it>
2007-05-26 16:38 ` double exclamation (!!) suckage in the kernel Bodo Eggert
2007-05-26 16:50 ` Al Viro [this message]
2007-05-29 8:26 ` Bodo Eggert
2007-05-25 20:23 Satyam Sharma
2007-05-25 20:28 ` Russell King
2007-05-25 20:32 ` Satyam Sharma
2007-05-25 20:37 ` Björn Steinbrink
2007-05-25 20:41 ` Al Viro
2007-05-25 20:56 ` Satyam Sharma
2007-05-25 21:03 ` Satyam Sharma
2007-05-25 21:32 ` Al Viro
2007-05-25 21:36 ` Al Viro
2007-05-25 21:37 ` Satyam Sharma
2007-05-25 21:14 ` David Miller
2007-05-26 13:41 ` Jan Engelhardt
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