Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!wuarchive!zaphod.mps.ohio-state.edu!rpi!crdgw1!underdog!volpe
From: volpe@underdog.crd.ge.com (Christopher R Volpe)
Newsgroups: comp.std.c
Subject: Re: static int x[2], *p = x+(x-x);  ?
Message-ID: <11907@crdgw1.crd.ge.com>
Date: 14 Sep 90 20:05:56 GMT
References: <1990Sep14.015241.2152@twinsun.com> <2699@rossignol.Princeton.EDU>
Sender: news@crdgw1.crd.ge.com
Reply-To: volpe@underdog.crd.ge.com (Christopher R Volpe)
Lines: 16

In article <2699@rossignol.Princeton.EDU>, drh@cs.Princeton.EDU (Dave
Hanson) writes:
|>        static int *s = x + (x-x); /* Does this ``evaluate to'' x+0? */
|>
|>even though (x-x) is 0, compilers may not be obliged
|>to recognize it as 0 because x-x doesn't conform to the allowable
|>expressions you listed above.

Yes, they are obliged to recognize it as zero because the two 
operands (which happen to be identical) are both pointers into
the same array. See K&R II A7.7
                                    
==================
Chris Volpe
G.E. Corporate R&D
volpecr@crd.ge.com