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Posting-Version: version B 2.10.1 6/24/83; site hcrvx1.UUCP
Path: utzoo!hcradm!hcrvx1!hugh
From: hugh@hcrvx1.UUCP (Hugh Redelmeier)
Newsgroups: net.lang.c
Subject: Re: C Compiler bug (a mutant strain)
Message-ID: <1380@hcrvx1.UUCP>
Date: Thu, 24-Jul-86 11:34:25 EDT
Article-I.D.: hcrvx1.1380
Posted: Thu Jul 24 11:34:25 1986
Date-Received: Fri, 25-Jul-86 05:23:59 EDT
References: <501@bunny.UUCP> <6224@allegra.UUCP>
Reply-To: hugh@hcrvx1.UUCP (Hugh Redelmeier)
Organization: Human Computing Resources, Toronto
Lines: 14

In article <6224@allegra.UUCP> mp@allegra.UUCP (Mark Plotnick) writes:
>The i /= f and i *= f bugs occur in the 4.3bsd-beta and 4.2bsd
>compilers...  The 4.3bsd and System V VAX compilers do the right thing.

Well, not so fast.  Many System V compilers (I don't know about
4.3BSD -- we haven't gotten it yet!) have a bug in the fix to this
bug!  Try "*p++ /= f;" where p is "int *": the ++ gets done twice.
In fact, any side-effect on the left-hand-side would be done twice.
Allen McIntosh of HCR has fixed this (with some effort) as part of our
optimizer project (we produce a portable optimizer that fits into PCC
and f77).

Hugh Redelmeier (416) 922-1937
{utzoo, ihnp4, decvax}!hcr!hugh