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From: Andreas Schwab <schwab@suse.de>
To: "Dave Korn" <dave.korn@artimi.com>
Cc: "'Daniel Berlin'" <dberlin@dberlin.org>, <mrc.lrn@inwind.it>,
	<gcc@gcc.gnu.org>
Subject: Re: Pointers in comparison expressions
References: <SERRANOIXMP9oxHETEW000004de@SERRANO.CAM.ARTIMI.COM>
X-Yow: ..  he dominates the DECADENT SUBWAY SCENE.
Date: Tue, 12 Jul 2005 21:00:00 -0000
In-Reply-To: <SERRANOIXMP9oxHETEW000004de@SERRANO.CAM.ARTIMI.COM> (Dave Korn's
	message of "Tue, 12 Jul 2005 17:54:00 +0100")
Message-ID: <jeu0izrb99.fsf@sykes.suse.de>
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"Dave Korn" <dave.korn@artimi.com> writes:

>   Since pointer subtraction is well defined, and it returns an int, then ...
>
> int *a, *b;
>
>   if (a < b)
>     dosomething ();
>
> ... is just the same as ...
>
> int *a, *b;
>
>   if ((b - a) >= 0)
>     dosomething ();

This may not work correctly if ((char*) b - (char*) a) % sizeof int != 0
(which can happen if __alignof__ int < sizeof int).

Andreas.

-- 
Andreas Schwab, SuSE Labs, schwab@suse.de
SuSE Linux Products GmbH, Maxfeldstraße 5, 90409 Nürnberg, Germany
Key fingerprint = 58CA 54C7 6D53 942B 1756  01D3 44D5 214B 8276 4ED5
"And now for something completely different."