Path: utzoo!utgpu!water!watmath!clyde!rutgers!mit-eddie!uw-beaver!tektronix!zeus!tekla!dant
From: dant@tekla.TEK.COM (Dan Tilque;1893;92-789;LP=A;60aC)
Newsgroups: comp.lang.c
Subject: Dereferencing zero
Message-ID: <2953@zeus.TEK.COM>
Date: 11 Jan 88 19:38:46 GMT
References: <3306@ihlpf.ATT.COM> <7010@brl-smoke.ARPA> <1561@rtech.UUCP>
Sender: news@zeus.TEK.COM
Reply-To: dant@tekla.UUCP (Dan Tilque)
Organization: Church of Christ, Secular Humanist
Lines: 22

Jim Shankland writes:
>
>	Code that dereferences 0 is buggy.  If I
>write such buggy code, I want to hear about it immediately by getting
>an access violation when I do the dereference.  I DON'T want my application
>to continue running, possibly doing horrible things, because the language
>implementor tried to do me a favor by covering up my bug.

While *0 is bad and should be appropriately flagged, sometimes you need to
reference a structure that begins at location zero.  For example:

	struct system_vectors	*svp;

	svp = 0;
	(svp->whatever_vector)();

Of course, this only works in supervisor mode on most machines, but
sometimes you have to do it.

---
Dan Tilque
dant@tekla.tek.com  or dant@tekla.UUCP