Path: utzoo!mnetor!uunet!seismo!sundc!pitstop!sun!amdcad!ames!pasteur!ucbvax!ulysses!hector!jss
From: jss@hector.UUCP (Jerry Schwarz)
Newsgroups: comp.lang.c
Subject: Re: "Noalias" warning and questions
Message-ID: <10080@ulysses.homer.nj.att.com>
Date: 15 Feb 88 18:47:34 GMT
References: <8012@elsie.UUCP> <7249@brl-smoke.ARPA>
Sender: netnews@ulysses.homer.nj.att.com
Reply-To: jss@hector (Jerry Schwarz)
Organization: AT&T Bell Labs, Murray Hill
Lines: 22

In article <7249@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>In article <8012@elsie.UUCP> ado@elsie.UUCP (Arthur David Olson) writes:
>
>This is not new; in earlier working drafts this injunction was given
>in English near the beginning of Section 4; now it is expressed more
>directly in the function interface definitions, using "noalias".
>The one hold-out is memmove(), which explicitly DOES permit overlap.
>
>If "noalias" should disappear (a distinct possibility!), we would
>have to put back the English injunction against overlapping *arguments.
>

You still need the English words. All "noalias" says is that certain
patterns of referencing using the pointers are undefined, unless you
know what patterns the function will use you don't know what
arguments will result in undefined behavior. In strcpy for example
you still need words to tell you that  there cannot be overlap.

As another recent item pointed out, in strcmp you need something else
(const) to tell you that the "noalias" in the declarations are noise.

Jerry Schwarz