Re: [BUG] Bad #define, nonportable C, missing {}

From: Andreas Schwab (schwab@suse.de)
Date: Wed Nov 21 2001 - 09:25:02 EST

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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, Schanzäckerstr. 10, D-90443 Nürnberg
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