Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!uflorida!haven!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: Null revisited (briefly)
Message-ID: <15820@mimsy.UUCP>
Date: 6 Feb 89 04:13:09 GMT
References: <13068@steinmetz.ge.com> <7630@chinet.chi.il.us>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 27

In article <7630@chinet.chi.il.us> les@chinet.chi.il.us
(Leslie Mikesell) writes:
>Does the (IMHO) incorrect cast of NULL to (char *) in some compilers
>stdio.h hurt anything in a correctly written program?

That (not just opinion) incorrect definition of NULL does indeed hurt.
For instance, given the (correct) C code:

	#include <stdio.h>
	int *ip = NULL;

the compiler should at least warn about the improper assignment of
(char *)0 to a variable of type (int *).  A compiler with such a
definition is likely to warn about or refuse to compile a large number
of correct programs.

Once again, the *ONLY* correct definitions of NULL are

	#define NULL 0
	#define NULL 0L
	#define NULL ((void *)0)

and possibly other constant expressions that evaluate to 0, 0L,
or (void *)0 anyway.  (char *)0 is *not* a proper untyped nil pointer.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris