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From: newman@mit-hector.UUCP (Ron Newman)
Newsgroups: net.lang.c
Subject: if (p), where p is a pointer
Message-ID: <118@mit-hector.UUCP>
Date: Tue, 10-Sep-85 23:31:46 EDT
Article-I.D.: mit-hect.118
Posted: Tue Sep 10 23:31:46 1985
Date-Received: Thu, 12-Sep-85 22:21:44 EDT
Organization: MIT Project Athena
Lines: 22

With all this talk about NULL pointers not necessarily being equal to 0,
I'm no longer sure what is and isn't portable code.  An C idiom I see 
(and write) frequently is

	<some type> *ptr;
	...
	if (ptr)
	   <statement>

Will this work correctly on a machine where NULL is not 0?  Does it really
need to say

	if (ptr != NULL)

??

(Disclaimer:  I've only known C and Unix for nine months, and have used only
Berkeley 4.2 and only on a VAX.   Thus the discussion about NULL and 0
being non-equivalent came as a great shock.)

/Ron Newman, MIT Project Athena