Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.csd.uwm.edu!lll-winken!uunet!mcsun!ukc!edcastle!aiai!richard
From: richard@aiai.ed.ac.uk (Richard Tobin)
Newsgroups: comp.lang.c
Subject: Re: Referencing NULL pointers
Message-ID: <823@skye.ed.ac.uk>
Date: 29 Aug 89 16:20:23 GMT
References: <32UP02Eg3d=801@amdahl.uts.amdahl.com> <1382@bruce.OZ> <10830@smoke.BRL.MIL> <9838@xanth.cs.odu.edu>
Reply-To: richard@aiai.UUCP (Richard Tobin)
Organization: AIAI, University of Edinburgh, Scotland
Lines: 20

In article <9838@xanth.cs.odu.edu> kremer@cs.odu.edu (Lloyd Kremer) writes:
>This is true for integral constant 0, but could you not access memory
>location 0 by writing:

>	p = 0;  /* integer variable that happens to be set to zero */
>	data = *(int *)p;  /* no constant expression in this line */

Probably, but there's nothing to stop a cast doing something strange.
This may work better (but of course is still completely unreliable):

   union {int i; int *p} x;

   x.i = 0;
   data = *x.p;

-- Richard
-- 
Richard Tobin,                       JANET: R.Tobin@uk.ac.ed             
AI Applications Institute,           ARPA:  R.Tobin%uk.ac.ed@nsfnet-relay.ac.uk
Edinburgh University.                UUCP:  ...!ukc!ed.ac.uk!R.Tobin