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Date: Mon, 30 Jan 2012 13:11:48 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Jonathan Corbet <corbet@lwn.net>
CC: Cyrill Gorcunov <gorcunov@openvz.org>, linux-kernel@vger.kernel.org,
        Andrew Morton <akpm@linux-foundation.org>,
        Pavel Emelyanov <xemul@parallels.com>,
        Serge Hallyn <serge.hallyn@canonical.com>,
        KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
        Kees Cook <keescook@chromium.org>, Tejun Heo <tj@kernel.org>,
        Andrew Vagin <avagin@openvz.org>,
        "Eric W. Biederman" <ebiederm@xmission.com>,
        Alexey Dobriyan <adobriyan@gmail.com>,
        Andi Kleen <andi@firstfloor.org>,
        KOSAKI Motohiro <kosaki.motohiro@gmail.com>,
        Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
        Glauber Costa <glommer@parallels.com>,
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        Eric Dumazet <eric.dumazet@gmail.com>,
        Vasiliy Kulikov <segoon@openwall.com>, Valdis.Kletnieks@vt.edu
Subject: Re: [patch cr 2/4] [RFC] syscalls, x86: Add __NR_kcmp syscall v7
References: <20120130140905.441199885@openvz.org> <20120130141852.309402052@openvz.org> <20120130125812.0075dd04@dt>
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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