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From: randy@umn-cs.UUCP (Randy Orrison)
Newsgroups: comp.lang.c,comp.unix.wizards
Subject: Re: pointer alignment when int != char *
Message-ID: <2130@umn-cs.UUCP>
Date: Fri, 28-Aug-87 10:02:33 EDT
Article-I.D.: umn-cs.2130
Posted: Fri Aug 28 10:02:33 1987
Date-Received: Sun, 30-Aug-87 05:56:42 EDT
References: <493@its63b.ed.ac.uk> <6061@brl-smoke.ARPA>
Reply-To: randy@umn-cs.UUCP (Randy Orrison)
Organization: UofM Math Department
Lines: 31
Xref: mnetor comp.lang.c:4006 comp.unix.wizards:3954

In article <483@mtxinu.UUCP> ed@mtxinu.UUCP (Ed Gould) writes:
>It's also not legal in the proposed ANSI C standard.  Pointers
>may be subtracted *only* if they point to members of the same
>array of elements.

How is this determined?  example:

int
strlen(s)
char *s;
{
	register char	*c;

	c = s;
	while(c++)
		;
	return (c-s);
}

How does anything know if s & c are pointing to members of the same array?
If s isn't 0 terminated, c could end up anywhere...

(No flames on off-by-one errors, or any design issues.  this is just an
example)

	-randy
-- 
Randy Orrison, University of Minnesota School of Mathematics
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