linux-kernel - Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR

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Message-ID: <4F270794.8030202@zytor.com>
Date:	Mon, 30 Jan 2012 13:11:48 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jonathan Corbet <corbet@....net>
CC:	Cyrill Gorcunov <gorcunov@...nvz.org>,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Emelyanov <xemul@...allels.com>,
	Serge Hallyn <serge.hallyn@...onical.com>,
	KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>,
	Kees Cook <keescook@...omium.org>, Tejun Heo <tj@...nel.org>,
	Andrew Vagin <avagin@...nvz.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Andi Kleen <andi@...stfloor.org>,
	KOSAKI Motohiro <kosaki.motohiro@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Glauber Costa <glommer@...allels.com>,
	Matt Helsley <matthltc@...ibm.com>,
	Pekka Enberg <penberg@...nel.org>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Vasiliy Kulikov <segoon@...nwall.com>, Valdis.Kletnieks@...edu
Subject: Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7

On 01/30/2012 11:58 AM, Jonathan Corbet wrote:
> 
> That's a cute trick, but do we know that every compiler that will ever see
> this code will use 1 for a true integer comparison?  Simply spelling it
> out with an if statement might be more robust, just as efficient, and, at
> the same time, easier for others to understand.
> 

This has been the case in C from the very beginning and is guaranteed by
the C standard.  The number of places which will break if this isn't
true is enormous.

	-hpa

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