Newsgroups: comp.lang.c
Path: utzoo!henry
From: henry@utzoo.uucp (Henry Spencer)
Subject: Re: calloc (actually NULL =?= 0)
Message-ID: <1989Apr13.172541.2024@utzoo.uucp>
Organization: U of Toronto Zoology
References: <22842@shemp.CS.UCLA.EDU> <1428@auspex.auspex.com> <987@atanasoff.cs.iastate.edu>
Date: Thu, 13 Apr 89 17:25:41 GMT

In article <987@atanasoff.cs.iastate.edu> hascall@atanasoff.cs.iastate.edu (John Hascall) writes:
>>>I always thought a pointer consisting of zero bits is NULL. 
> 
>>Nope.  No such guarantee was ever made by any C language spec.
>
>   What about the following taken from K&R, Appendix A, section 7.14,
>   "Assignment operator":
>
>       However, it is guaranteed that assignment of the
>       constant 0 to a pointer will produce a null pointer...

"Produce" a null pointer.  And note that it says *constant*.  An integer
constant 0 in a pointer context is C's odd way of writing the null pointer
as a constant.  This is purely a *notation*; it does not necessarily have
anything to do with the actual representation.  On seeing this curious
bit of notation, the compiler generates whatever bits are needed.
-- 
Welcome to Mars!  Your         |     Henry Spencer at U of Toronto Zoology
passport and visa, comrade?    | uunet!attcan!utzoo!henry henry@zoo.toronto.edu