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From: garry@batcomputer.tn.cornell.edu (Garry Wiegand)
Newsgroups: comp.lang.c
Subject: Re: Query: Implementation with non-zero NULL
Message-ID: <1217@batcomputer.tn.cornell.edu>
Date: Sat, 30-May-87 00:01:11 EDT
Article-I.D.: batcompu.1217
Posted: Sat May 30 00:01:11 1987
Date-Received: Sun, 31-May-87 19:38:22 EDT
Reply-To: garry@oak.cadif.cornell.edu
Organization: Cornell Engineering && Flying Moose Graphics
Lines: 30

In a recent article henry@delftcc.UUCP (Henry Rabinowitz) wrote:
>I'm writing a book on C portability.  Interested to find actual
>implementation of C where the null pointer is not "all bits zero."

And I'd be interested in knowing what difference it could ever make
to a portable program:  the only ways I know to look at the bits
is to union the pointer with an integer (and load the pointer &
look at the integer), or to cast the pointer to an integer. Both of which 
would be very forbidden in portable code.

>Are static pointers initialized to all bits zero or to the null value
>(as in ANSI spec)?

You should NEVER assume a not-explicitly-initialized static variable
is given any particular value by anybody.

Note: I have not yet seen a compiler written to the ANSI spec. Talking
about porting between ANSI-spec compilers is not a very interesting 
thing to do, and won't be for a while (five years, maybe?)

>In such an implementation, can you use the conventional abbreviation
>	if (p)
>to mean
>	if (p != NULL)

Um, might I suggest that this book project is not really a good idea for
you? And the world?  (Please see K&R on the meaning of 'if(p)').

garry wiegand   (garry@oak.cadif.cornell.edu - ARPA)
		(garry@crnlthry - BITNET)