Article View: comp.std.c
Article #615Re: volatile required?
From: Barry Margolin
Date: Thu, 28 Sep 1989 16:33
Date: Thu, 28 Sep 1989 16:33
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952 bytes
In article <712@Aragorn.dde.dk> ct@dde.dk (Claus Tondering) writes:
> int p=3, *q=&p;
> *q=4;
> printf("%d\n",p);
>Is it acceptable that this program prints 3 instead of 4? The variable
>p is not declared volatile, and therefore the fact that *q=4 assigns
>4 to p may be considered a side effect.
No, the program must print 4. Since p's address is taken, the
optimizer should know that it isn't safe to assume that only
assignments to p will modify its value.
Barry Margolin, Thinking Machines Corp.
barmar@think.com
{uunet,harvard}!think!barmar
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Path: arc1-ca.pugleaf.net!utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!nrl-cmf!think!kulla!barmar From: barmar@kulla (Barry Margolin) Newsgroups: comp.std.c Subject: Re: volatile required? Message-ID: <30292@news.Think.COM> Date: 28 Sep 89 16:33:46 GMT References: <712@Aragorn.dde.dk> Sender: news@Think.COM Organization: Thinking Machines Corporation, Cambridge MA, USA Lines: 16