Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!virtech!cpcahil
From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.unix.wizards
Subject: Re: What machines core dump on deref of NULL?
Message-ID: <1990Jun29.232656.20695@virtech.uucp>
Date: 29 Jun 90 23:26:56 GMT
References: <444@mtndew.UUCP> <31079@cup.portal.com> <13226@smoke.BRL.MIL> <412@minya.UUCP>
Reply-To: cpcahil@virtech.UUCP (Conor P. Cahill)
Organization: Virtual Technologies Inc., Sterling VA
Lines: 29

In article <412@minya.UUCP> jc@minya.UUCP (John Chambers) writes:
>Hey, wait just a minute here.  I can't let such an erroneous error go
>unchallenged!  Dereferencing a null pointer is quite definitely *not*
>an error, bug, mistake, or any other pejorative, in a great many sorts
>of applications.
>
>The trouble with generalizing to all C code is that C outgrew Unix
>about a decade ago.

HOWEVER, this is not comp.lang.c.  This comp.unix.whatever and in this
context dereferencing a null pointer is, or should be, a no-no.  Any 
unix code that does, has at least 1 serious bug that should be fixed.

I remember one time when I was porting some code to a sun 3 and 
ran across the following line of code:

	if( strcmp(variable,(char*)0) == 0 )

I really wasn't sure what the original programmer was attempting to 
check (since the first byte at 0 was a null byte on the original machine),
so I changed the code to be:

	if( (variable == (char *)0) || (*variable == '\0'))


-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170