Path: utzoo!attcan!uunet!cs.utexas.edu!wuarchive!texbell!sugar!ficc!peter
From: peter@ficc.uu.net (Peter da Silva)
Newsgroups: comp.lang.c
Subject: Re: effect of free()
Message-ID: <6117@ficc.uu.net>
Date: 10 Sep 89 14:54:46 GMT
References: <319@cubmol.BIO.COLUMBIA.EDU> <3756@buengc.BU.EDU> <2071@munnari.oz.au>
Organization: Xenix Support, FICC
Lines: 34

In article <2071@munnari.oz.au>, ok@cs.mu.oz.au (Richard O'Keefe) writes:
> It's as if
> 	p = 1;
> 	printf("%d\n", p);
> 	if (p == 0)
> were allowed to blow up.

Try this:
	foo = GetPointerToSharedMemory();
	DeleteSharedMemory();
	if(foo==0);

There will always be cases like this. It just so happens that it may be
desirable to make free() one of these cases. So the standard does not preclude
it.

> The problem with address loads trapping is not a hardware problem; it is a
> hardware/OS problem.

Yes.

> I have outlined one approach which requires some OS
> cooperation, but if the standard required the usual invariance property to
> hold, OS vendors just might see an advantage in making C implementation
> straightforward.

The standard deliberately avoids doing this sort of thing. How about the
limitation in significant characters in extyernal symbols? That one's much
more irritating.
-- 
Peter da Silva, *NIX support guy @ Ferranti International Controls Corporation.
Biz: peter@ficc.uu.net, +1 713 274 5180. Fun: peter@sugar.hackercorp.com. `-_-'
"...the TV reporters, who are as intelligent as electric toasters"         'U`
	-- Clayton E. Cramer