Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!usc!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!unmvax!pprg.unm.edu!topgun!mustang!nntp-server.caltech.edu!seismo.gps.caltech.edu!bruce
From: bruce@seismo.gps.caltech.edu (Bruce Worden)
Newsgroups: comp.lang.c
Subject: Re: BSD bzero() & NULL
Message-ID: <1990Nov14.225031.12105@nntp-server.caltech.edu>
Date: 14 Nov 90 22:50:31 GMT
References: <AbEJW8e00VQfE4N0I3@andrew.cmu.edu>
Sender: bruce@seismo.gps.caltech.edu (Bruce Worden)
Organization: California Institute of Technology, CA
Lines: 28
Nntp-Posting-Host: sis.gps.caltech.edu

In article <AbEJW8e00VQfE4N0I3@andrew.cmu.edu> jl57+@andrew.cmu.edu (Jay Laefer) writes:

>char *fred;
>fred = 0;
> [ .... ]
>But, given that bzero() directly fills an area with zeros, can I assume
>that the following is equivalent to the above?

>bzero(fred, sizeof (char *))

>My gut reaction is no because this zeros out a block of memory and I'm
>not guaranteed that the computer's internal representation of NULL is a
>zero bit pattern.

It won't work, but not for the reason you stated.  bzero() will zero out 
sizeof(char *) bytes starting at the address `fred', which has not been 
initialized, so you will simply be zeroing out some memory at a random 
location.  I imagine that you meant to ask whether

	bzero((char *)&fred, sizeof(char *));

will work, in general.  And the answer is no, for the reason you stated.
(There may also be an issue as to whether (char *)&fred is an acceptable
argument to bzero().)  BTW, memset() would probably be better in an ANSI C 
program, since it is defined by the standard, and bzero() is not.
--------------------------------------------------------------------------
C. Bruce Worden                            bruce@seismo.gps.caltech.edu
252-21 Seismological Laboratory, Caltech, Pasadena, CA 91125