Newsgroups: comp.lang.c
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From: scs@adam.mit.edu (Steve Summit)
Subject: Re: Evaluation of if's
Message-ID: <1991Jun4.233928.5185@athena.mit.edu>
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Reply-To: scs@adam.mit.edu
Organization: Thermal Technologies, Cambridge, MA
References: <FPB.91Jun4174400@ittc.ittc.wec.com>
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Date: Tue, 4 Jun 91 23:39:28 GMT
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In article <FPB.91Jun4174400@ittc.ittc.wec.com> fpb@ittc.wec.com (Frank P. Bresz) writes:
>	if ( (i=1) == (i=2) )
>
>Is somebody wrong or is the behavior undefined?
>Personal opinion: I think the behaviour is undefined by K&R anyway I can't
>say for ANSI.

Of course it's undefined.  (It contains two side effects not
separated by a sequence point.)  Given that the behavior is
undefined, I'd say it's fairly pointless to catalog the behavior
of available compilers.  As Kernighan and Ritchie point out, and
I am fond of quoting, "if you don't know how they are done on
various machines, that innocence may help to protect you."

The comp.lang.c frequently-asked questions list has a bit to say
about undefined order of evaluation.  Did you check it first?

                                            Steve Summit
                                            scs@adam.mit.edu