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From: guy%gorodish@Sun.COM (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: Query: Implementation with non-zero NULL
Message-ID: <20028@sun.uucp>
Date: Fri, 29-May-87 14:01:30 EDT
Article-I.D.: sun.20028
Posted: Fri May 29 14:01:30 1987
Date-Received: Sun, 31-May-87 07:46:39 EDT
References: <158@delftcc.UUCP>
Sender: news@sun.uucp
Lines: 28
Keywords: C, NULL, portability

> I'm writing a book on C portability.  Interested to find actual
> implementation of C where the null pointer is not "all bits zero."

Try looking for a machine with lots of instruction-set features for
type checking *et al*; such a machine might have some special format
for a null pointer.

> (List of questions about the implementation)

One hopes that the implementation will do the "right thing" in all
those cases.  This does not guarantee that there is not an
implementation that does the wrong thing, it just means that if there
is such an implementation, it has bugs in it and should be fixed, and
that the implementer has no leg to stand on if they want to defend
the implementation.  *I* certainly don't intend to alter my code on
the off chance that somebody who didn't understand C did the
implementation; were I to come across such an implementation, I would
inform them that their implementation was broken.

BTW,

	char *p; p = 0;

will also result in assigning a null pointer to "p" on a correct
implementation.
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com