Re: gcc -O2 bug

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#3664

From: Orc
Date: Thu, 08 Aug 1996 00:00

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In article <4ubnat$75u@freeside.fc.net>,
Mike Big <mrbig@freeside.fc.net> wrote:
>/* 
>I'v found what I think might be a bug in gcc's optimization.

Not a bug; a feature.

Your code is being optimised away; gcc thinks that 'while(flag)'
is always true when you optimize with -O2.

If you convert your flag declaration to 'volatile int flag;' it will
subvert the optimisations.  (Check the ANSI standard; the code you've
got is almost the textbook example of why 'volatile' was created.)

                 ____
   david parsons \bi/ followups set to the proper place.
                  \/

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From: orc@pell.chi.il.us (Orc)
Subject: Re: gcc -O2 bug
Date: 1996/08/08
Message-ID: <4udnqu$vv6@pell.pell.chi.il.us>
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references: <4ubnat$75u@freeside.fc.net>
followup-to: comp.std.c
organization: I *plonk* LA
keywords: gcc bug O2
newsgroups: comp.unix.programmer,gnu.gcc.help,comp.os.linux.development.apps,comp.lang.c

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