Path: utzoo!mnetor!uunet!lll-winken!lll-tis!ames!ncar!oddjob!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Referencing through a null pointer
Message-ID: <11199@mimsy.UUCP>
Date: 24 Apr 88 11:09:50 GMT
References: <4729@cup.portal.com>
Distribution: na
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 16

In article <4729@cup.portal.com>, Paul_L_Schauble@cup.portal.com writes:
>Could someone please tell me which machine it was that started the
>unfortunate convention that referencing through the null pointer returns a
>zero with no error? I was under the impression it was BSD Unix, but I'm not
>sure.

PDP-11s with split I&D had a shim at data address zero; I believe the
shim was a zero.  (The shim is necessary to keep the first data object
from having an address that compares equal to NULL.)

I imagine that PDP-11s without split I&D had *(char *)0 == 7 or 8, and
*(short *)0 == 0407 or 0408 (OMAGIC and NMAGIC respectively).

32V Unix had *(int *)0==0.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris