Path: utzoo!utgpu!watmath!att!tut.cis.ohio-state.edu!cs.utexas.edu!uunet!virtech!cpcahil
From: cpcahil@virtech.UUCP (Conor P. Cahill)
Newsgroups: comp.lang.c
Subject: Re: "do ... while ((NULL + 1) - 1);" -- valid C?
Message-ID: <961@virtech.UUCP>
Date: 8 Aug 89 01:44:06 GMT
References: <1043@levels.sait.edu.au>
Organization: Virtual Technologies Inc
Lines: 17

In article <1043@levels.sait.edu.au>, ccdn@levels.sait.edu.au (DAVID NEWALL) writes:
> 
> I've been told that this is not valid C because, in the case that there
> are no more fields (commas), strchr() returns NULL; and NULL + 1 is not
> valid.

NULL, in this case, is just a pointer that has the value 0.  NULL + 1 is a valid
operations, however *(NULL+1) is not.

I wouldn't code the loop as you have displayed because one has to
spend time thinking about what the will is  trying to do.  A "better" method
would be something like:

		do 
		   ...;
		   s = strchr(s,','); 
		while ( s++ != NULL );