Path: utzoo!mnetor!uunet!husc6!rutgers!iuvax!pur-ee!uiucdcs!uxc.cso.uiuc.edu!uxe.cso.uiuc.edu!mcdonald
From: mcdonald@uxe.cso.uiuc.edu
Newsgroups: comp.lang.c
Subject: Re: `noalias' vs `register'
Message-ID: <47000026@uxe.cso.uiuc.edu>
Date: 17 Dec 87 14:26:00 GMT
References: <9817@mimsy.UUCP>
Lines: 32
Nf-ID: #R:mimsy.UUCP:9817:uxe.cso.uiuc.edu:47000026:000:726
Nf-From: uxe.cso.uiuc.edu!mcdonald    Dec 17 08:26:00 1987


>>	f() {
>>		register int r;
>>		...
>>		r = 1;
>>		g();
>>		if (r == 1) ...
>>Does the `if' succeed?  Yes, because there is no way for g() to
>>alter `r'.

>That is true for any auto; "register" has nothing to do with it!
>If you mean that there is no way to form a pointer to r, that is
>of course correct, but a red herring.


 Really?

      int *xxxx;

       f() {
                int r;
                xxxx = &r;
                 r = 1;
                 g();
                 printf("%d",r); }
        g(){ *xxxx += 5 ;}

What would happen if I had said " noalias int r" ? From what has been said,
I have no earthly idea. ( Is it an error? If the compiler could recognize it
as an error, why have it?)

Doug McDonald