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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
Date: Tue, 12 Jul 2005 21:00:00 -0000	[thread overview]
Message-ID: <jeu0izrb99.fsf@sykes.suse.de> (raw)
In-Reply-To: <SERRANOIXMP9oxHETEW000004de@SERRANO.CAM.ARTIMI.COM> (Dave Korn's message of "Tue, 12 Jul 2005 17:54:00 +0100")

"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."

  reply	other threads:[~2005-07-12 21:00 UTC|newest]

Thread overview: 26+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2005-07-12 16:24 Mirco Lorenzoni
2005-07-12 16:32 ` Daniel Berlin
2005-07-12 16:53   ` Dave Korn
2005-07-12 21:00     ` Andreas Schwab [this message]
2005-07-12 21:42     ` Erik Trulsson
2005-07-12 22:09       ` Joe Buck
2005-07-12 22:28         ` Erik Trulsson
2005-07-12 22:38           ` Falk Hueffner
2005-07-12 23:17             ` Joe Buck
2005-07-12 23:28               ` Falk Hueffner
2005-07-13  2:02                 ` Joe Buck
2005-07-13 21:42                 ` Olivier Galibert
2005-07-12 23:27             ` Michael Meissner
2005-07-12 22:46           ` Joe Buck
2005-07-16 11:49       ` Vincent Lefevre
2005-07-17 16:55         ` Paul Koning
2005-07-18  1:49           ` Vincent Lefevre
2005-07-18  3:13             ` D. Hugh Redelmeier
2005-07-18 13:13               ` Paul Koning
2005-07-18 13:09             ` Paul Koning
2005-07-12 17:03 ` chris jefferson
2005-07-12 23:18 ` Michael Meissner
2005-07-22 23:20 ` Geoffrey Keating
2005-07-13 13:53 Morten Welinder
2005-07-24  1:13 Paul Schlie
2005-07-26  4:43 ` Geoff Keating

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