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To: Vincent Sweeney <v.sweeney@dexterus.com>
Cc: vda <vda@port.imtp.ilyichevsk.odessa.ua>, linux-kernel@vger.kernel.org
Subject: Re: [BUG] Bad #define, nonportable C, missing {}
In-Reply-To: <01112112401703.01961@nemo> <3BFB9FAE.DB9B6003@dexterus.com>
X-Yow: You mean you don't want to watch WRESTLING from ATLANTA?
From: Andreas Schwab <schwab@suse.de>
Date: 21 Nov 2001 15:25:02 +0100
In-Reply-To: <3BFB9FAE.DB9B6003@dexterus.com> (Vincent Sweeney's message of "Wed, 21 Nov 2001 12:35:58 +0000")
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Vincent Sweeney <v.sweeney@dexterus.com> writes:

|> vda wrote:
|> > ------------------------------------------------------------------
|> > Undefined behavior by C std: inc/dec may happen before dereference.
|> > Probably GCC is doing inc after right side eval, but standards say nothing
|> > about it AFAIK. Move ++ out of the statement to be safe:
|> >     *a++ = byte_rev[*a]; => *a = byte_rev[*a]; a++;
|> 
|> C std says *always* evaluate from right to left for = operators, so this
|> will always make perfect sense.

No.  It is undefined which of the operator's arguments is evaluated first,
unless it is defined otherwise (only for ||, && and comma).

Andreas.

-- 
Andreas Schwab                                  "And now for something
Andreas.Schwab@suse.de				completely different."
SuSE Labs, SuSE GmbH, Schanz?ckerstr. 10, D-90443 N?rnberg
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