linux-kernel - Re: Conversion to generic boolean

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Message-ID: <20060829114143.GB4076@infradead.org>
Date:	Tue, 29 Aug 2006 12:41:43 +0100
From:	Christoph Hellwig <hch@...radead.org>
To:	Nicholas Miell <nmiell@...cast.net>
Cc:	Richard Knutsson <ricknu-0@...dent.ltu.se>,
	Jan Engelhardt <jengelh@...ux01.gwdg.de>,
	Christoph Hellwig <hch@...radead.org>,
	James.Bottomley@...elEye.com, linux-scsi@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Conversion to generic boolean

On Mon, Aug 28, 2006 at 12:15:40PM -0700, Nicholas Miell wrote:
> > That is error-prone. Not "==FALSE" but what happens if x is (for some 
> > reason) not 1 and then "if (x==TRUE)".
> 
> If you're using _Bool, that isn't possible. (Except at the boundaries
> where you have to validate untrusted data -- and the compiler makes that
> more difficult, because it "knows" that a _Bool can only be 0 or 1 and
> therefore your check to see if it's not 0 or 1 can "safely" be
> eliminated.)

gcc lets you happily assign any integer value to bool/_Bool, so unless
you write sparse support for actually checking things there's not the
slightest advantage in value range checking.
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