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From: drw@cullvax.UUCP (Dale Worley)
Newsgroups: comp.lang.c
Subject: Distinguished pointers (was Re: Weird syscall returns)
Message-ID: <1437@cullvax.UUCP>
Date: Fri, 7-Aug-87 13:25:12 EDT
Article-I.D.: cullvax.1437
Posted: Fri Aug  7 13:25:12 1987
Date-Received: Sun, 9-Aug-87 02:58:31 EDT
Organization: Cullinet Software, Westwood, MA, USA
Lines: 31

guy%gorodish@Sun.COM (Guy Harris) writes:
> [The Draft Standard] says, apropos of equality operators,
> 
> 	If two pointers to objects or functions compare equal, they
> 	point to the same object or function, respectively.
> 
> which pretty clearly indicates that comparison of pointers for
> equality is meant to work regardless of whether the two pointers
> point into the same array or not.

This statement leaves a really nasty ambiguity:  If two pointers
compare *unequal*, then do they *not* point to the same thing?  It
seems possible that an implementation could have multiple
representations of pointers to a particular object, but how are we to
make sure that

	int X[10];
	int *a, *b;
	a = X;
	b = X;
	a++;
	b++;
	a == b

always returns true?

Dale
-- 
Dale Worley	Cullinet Software		ARPA: cullvax!drw@eddie.mit.edu
UUCP: ...!seismo!harvard!mit-eddie!cullvax!drw
OS/2: Yesterday's software tomorrow	    Nuclear war?  There goes my career!