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From: richard@aiva.ed.ac.uk (Richard Tobin)
Newsgroups: comp.lang.c
Subject: Re: Distinguished pointers (was Re: Weird syscall returns)
Message-ID: <142@aiva.ed.ac.uk>
Date: Sun, 9-Aug-87 14:58:41 EDT
Article-I.D.: aiva.142
Posted: Sun Aug  9 14:58:41 1987
Date-Received: Tue, 11-Aug-87 00:59:30 EDT
References: <1158@copper.TEK.COM> <8317@utzoo.UUCP> <123@aiva.ed.ac.uk> <25045@sun.uucp>
Reply-To: richard@uk.ac.ed.aiva (Richard Tobin)
Distribution: comp
Organization: AI Applications Institute, Edinburgh University
Lines: 33
Summary: Looks like I've got an out-of-date draft

In article <25045@sun.uucp> guy%gorodish@Sun.COM (Guy Harris)
writes (in reply to me):

>> "If the objects pointed to are not members of the same aggregate object, the
>> result is undefined"
>The October 1, 1986 draft says this apropos of relational operators
>on pointers, but !NOT! apropos of equality operators.  Does your
>draft says this even about comparisons for equality?

No, but it doesn't say this either (at least not in the section entitled
"C.3.9 Equality operators"):

>	If two pointers to objects or functions compare equal, they
>	point to the same object or function, respectively.

All it says is:

"The == (equal to) and the != (not equal to) operators are analogous to
the relational operators except for their lower precedence."

So it seems that the standard has been clarified since the version
I have.

>For *equality* operators, it is clear that they want to *forbid*
>segmented architectures from just comparing the segment offset; doing
>the comparison that way would be horribly bogus and stupid.

It certainly would, which is why I wanted to check up on it.  Thanks
for your help.
-- 
Richard Tobin,                           JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,               ARPA:  R.Tobin%uk.ac.ed@cs.ucl.ac.uk
Edinburgh University.                    UUCP:  ...!ukc!ed.ac.uk!R.Tobin