Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!apple!ames!uhccux!munnari.oz.au!bruce!mmcg
From: mmcg@bruce.OZ (Mike  Mc Gaughey)
Newsgroups: comp.unix.wizards
Subject: Re: Referencing NULL pointers
Message-ID: <1382@bruce.OZ>
Date: 16 Jul 89 02:49:53 GMT
References: <32UP02Eg3d=801@amdahl.uts.amdahl.com>
Organization: Monash Uni. Computer Science, Australia
Lines: 21

vohra@uts.amdahl.com (Pavan Vohra) [11 Jul 89 07:35:39 GMT]:
> 
> I would say that the code is valid.
> 
> Try a rewrite: "x= ((struct somestruct *)0)->somefield".

Sure it's valid.  It's just that the pointer value you are using does
not point to any valid object (like a variable, or some heap space, or
writable code) and hence may not point to allocated memory.  Result:
segmentation violation.  If you want to hardwire a particular address,
that's up to you - maybe some useful information is there - but don't
bitch when it doesn't work on someone else's machine.

BTW: There _is_ a way to guarantee that you have a valid pointer -
it's called malloc :-)

--
Mike McGaughey			ACSNET:	mmcg@bruce.cs.monash.oz

"Danger, Will Robinson, cosmic storm approaching!"
	- in bruce's /vmunix.