Path: utzoo!attcan!uunet!snorkelwacker!spdcc!ima!haddock!karl
From: karl@haddock.ima.isc.com (Karl Heuer)
Newsgroups: comp.lang.c
Subject: Re: Is "if (!pointer)" as portable as "if (pointer == NULL)" ???
Keywords: portability, pointers, NULL
Message-ID: <16437@haddock.ima.isc.com>
Date: 11 Apr 90 16:40:29 GMT
References: <656@hades.OZ>
Reply-To: karl@haddock.ima.isc.com (Karl Heuer)
Organization: Interactive Systems, Cambridge, MA 02138-5302
Lines: 19

In article <656@hades.OZ> greyham@hades.OZ (Greyham Stoney) writes:
>But can you also just do an aritmetic check on the cast value of the pointer?:

No.

>K&R says that casting anything with a value 0 to a pointer yeilds a NULL
>pointer; so presumably casting a NULL pointer back to value yeilds a zero.

Not necessarily.

>	if (buffer = malloc(50))	/* yes, that SHOULD be =, not == */
>	if (buffer) free(buffer)

But these are acceptable (if you like that style, which I don't).  You seem to
believe that `if (buffer)' means `if ((int)buffer != 0)' (which would not be
a valid test), but in fact it means `if (buffer != (char *)0)' (which is quite
correct).

Karl W. Z. Heuer (karl@ima.ima.isc.com or harvard!ima!karl), The Walking Lint