Path: utzoo!attcan!utgpu!jarvis.csri.toronto.edu!rutgers!usc!polyslo!vlsi3b15!mpx1!mpx2!erik
From: erik@mpx2.mpx.com (Erik Murrey)
Newsgroups: comp.lang.c
Subject: use of if (!cptr) and if (cptr), where cptr is a *
Keywords: * != int
Message-ID: <10099@mpx2.mpx.com>
Date: 17 Jul 89 12:29:41 GMT
Reply-To: erik@mpx2.mpx.com (Erik Murrey)
Organization: MPX Data Systems, Inc. ,  Wayne, PA
Lines: 48


I'm curious how the gods feel about testing pointers in the following
way (by example):

char	*cptr, *malloc();	/* ok, so maybe malloc is void * by now... */

x()
{
	cptr= malloc(...);
	if (!cptr)
		fatal("cannot malloc");
	...
}

I know that sizeof(char *) != sizeof(int) on some machines, but the test
of (!cptr) is for zero.  It sure looks a lot better when you are testing
complex pointers:

struct xyzzy	*sptr;
char		*malloc();

x()
{
	sptr= (struct xyzzy *)malloc(...);
	if (sptr == (struct xyzzy *)NULL)	/* (!sptr) would look better */
		fatal("cannot malloc");
}

Would (!sptr) break anywhere?  Should it be discouraged?

In fact, I much prefer (from a C style article posted a few years back):

x()
{
	if (sptr= (struct xyzzy *)malloc(...), !sptr)
		fatal("cannot malloc");
}

Any problems with this?

Thanks for your input.  E-mail if you feel it is appropriate.

... Erik
-- 
Erik Murrey                            /|   //  /~~~~/  |  /
MPX Data Systems, Inc.                / | / /  /____/   |/
erik@mpx.com                         /  /  /  /        /|  Data Systems, Inc. 
{vu-vlsi, bpa, cbmvax}!mpx1!erik    /     /  /       /  |====================