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From: caf@omen.UUCP (Chuck Forsberg WA7KGX)
Newsgroups: net.unix-wizards
Subject: Re: Xenix286 Wonders, Bugs, and Patches...
Message-ID: <160@omen.UUCP>
Date: Wed, 15-May-85 14:50:57 EDT
Article-I.D.: omen.160
Posted: Wed May 15 14:50:57 1985
Date-Received: Fri, 17-May-85 00:16:11 EDT
References: <10550@brl-tgr.ARPA>
Organization: Omen Technology, Portland
Lines: 29

>NULL is usually declared in stdio.h as:
>	#define NULL 0
>Kernighan & Ritchie on page 98 state explicitly that, "In general, integers
>cannot meaningfully be assigned to pointers; zero is a special case."  On the
>previous page they state, "C guarantees that no pointer that validly points at
>data will contain zero, ..."
>
>Thus, the code is not buggy in the least; with or without casting.  If code
>such as:
>	struct mumble *p;
>	...
>	p = 0;
>does not assign a 32-bit wide zero on a machine with 16-bit int's and 32-bit
>pointers then you don't have a buggy program.  You have a buggy compiler that
>needs fixing.

The problem is not a buggy compiler (Lord knows there are enough to go
around in PC-AT Xenix) but the difficulty of transforming a sow's ear
(8086 segmmented CPU) into a silk purse (32 bit CPU).

Pushing an int onto the stack pushes 16 bits but a large model program
is expecting to get a 32 bit magic cookie (pointer to char).

Passing zero to a function is not as universal as assigning zero to
something.
-- 
Chuck Forsberg WA7KGX	..!tektronix!reed!omen!caf
Omen Technology Inc 17505-V NW Sauvie IS RD Portland OR 97231
Voice: 503-621-3406	Modem: 503-621-3746 (Hit CR's for speed detect)