linux-kernel - Re: [PATCH] strcmp: fix overflow error

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Message-ID: <m3lji5xdcm.fsf@hase.home>
Date:	Tue, 17 Nov 2009 18:36:41 +0100
From:	Andreas Schwab <schwab@...hat.com>
To:	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:	linux-kernel@...r.kernel.org, Michael Buesch <mb@...sch.de>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH] strcmp: fix overflow error

Uwe Kleine-König <u.kleine-koenig@...gutronix.de> writes:

> strcmp("\x01", "\xef") returns 18 but it should return something < 0.
> The reason is that the variable holding the result of the subtraction is
> too small and overflows.

When char is signed strcmp("\xef", "\x01") still returns something < 0.
You need to cast to unsigned char first.

Andreas.

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Andreas Schwab, schwab@...hat.com
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