Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!mailrus!csd4.milw.wisc.edu!bionet!ames!haven!adm!smoke!gwyn
From: gwyn@smoke.BRL.MIL (Doug Gwyn)
Newsgroups: comp.lang.c
Subject: Re: use of if (!cptr) and if (cptr), where cptr is a *
Message-ID: <10544@smoke.BRL.MIL>
Date: 17 Jul 89 15:34:44 GMT
References: <10099@mpx2.mpx.com>
Reply-To: gwyn@brl.arpa (Doug Gwyn)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 12

In article <10099@mpx2.mpx.com> erik@mpx2.mpx.com (Erik Murrey) writes:
>Would (!sptr) break anywhere?  Should it be discouraged?

When sptr is a pointer variable, the following are equivalent:
	if(!sptr)
	if(sptr==0)
	if(sptr==NULL)	/* assuming NULL is properly defined */
There is no need to cast the 0 (or NULL) to the type of sptr for this
comparison.

A common idiom is
	if ( (sptr = (type *)malloc( size )) == NULL )