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Posting-Version: version B 2.10.2 9/18/84; site dciem.UUCP
Path: utzoo!dciem!msb
From: msb@dciem.UUCP (Mark Brader)
Newsgroups: net.lang.c
Subject: Re: ANSI C
Message-ID: <1917@dciem.UUCP>
Date: Fri, 15-Aug-86 12:34:43 EDT
Article-I.D.: dciem.1917
Posted: Fri Aug 15 12:34:43 1986
Date-Received: Fri, 15-Aug-86 13:24:10 EDT
References: <86900009@haddock> <6143@sun.uucp>
Reply-To: msb@dciem.UUCP (Mark Brader)
Organization: NTT Systems Inc., c/o DCIEM, Toronto
Lines: 18
Summary: 

Somebody writes:

> > In 3.2.2.3, "(void *)0" is called a null pointer constant, though 5.6.3.12
> > says the value of NULL is implementation-defined.  I take this to mean that
> > the internal representation of (void *)0 need not have all bits clear.

Guy Harris (guy@sun.uucp) replies:

> Yes.  I'm certain there are many machines out there that either have C
> implementations or should have them that have a representation for null
> pointers that is not a bucket of zero bits.

This is almost correct.  It IS true that (void *)0 need not have all bits
clear, but this is not what the reference in 5.6.3.12 is saying.  What it is
saying is that your implementation can #define NULL as either 0 or (void *)0.

Mark Brader, dciem!msb
#define	MSB(type)	(~(((unsigned type)-1)>>1))