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From: guy@sun.uucp (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: NULL function pointers
Message-ID: <27949@sun.uucp>
Date: Mon, 14-Sep-87 17:10:31 EDT
Article-I.D.: sun.27949
Posted: Mon Sep 14 17:10:31 1987
Date-Received: Wed, 16-Sep-87 01:36:07 EDT
References: <9268@brl-adm.ARPA>
Organization: Sun Microsystems, Inc. - Mtn View, CA
Lines: 18

> K&R guarantees pointers to valid data objects are non-NULL.  But what
> about function pointers?  I found no reference to guarantees to non-NULL
> function pointers and a number of compiler system/linkers I've seen have
> no problem inserting C functions at address 0.

The passage in question says "object", not "data object", and only a cad of an
implementor would interpret "object" as meaning "data object" here.  (Of
course, it is quite possible that some C implementors *are* cads; the
existence of systems that do not ensure that no function has an address that
compares equal to a null pointer would suggest that some are....)

The latest ANSI C draft says "object or function" in its discussion of null
pointers, thus restraining the aforementioned implementors and ensuring that C
implementations are sane in this regard.
-- 
	Guy Harris
	{ihnp4, decvax, seismo, decwrl, ...}!sun!guy
	guy@sun.com (or guy@sun.arpa)