Path: utzoo!attcan!uunet!auspex!guy
From: guy@auspex.UUCP (Guy Harris)
Newsgroups: comp.lang.c
Subject: Re: pointers, tests, casts
Message-ID: <494@auspex.UUCP>
Date: 23 Nov 88 17:50:42 GMT
References: <11130@dartvax.Dartmouth.EDU>
Reply-To: guy@auspex.UUCP (Guy Harris)
Organization: Auspex Systems, Santa Clara
Lines: 18

>In assignments, a 0 or NULL is cast implicitly to the correct pointer
>type (I think, please correct me if I'm wrong).

This is correct.

>What about the '==' comparison above?  Would "(ptr == 0)" get evaluated
>correctly?

In any valid C implementation, it will be.  The compiler certainly knows
enough to do the implicit conversion, just as it does in the case of an
assignment.

>Or to push it a bit further, what about the VAX-ish standard (like
>*(char *)0 = 0 ;-) "(!ptr)"?  I realize that it is probably better to
>explicitly cast & compare, but it did kind of make sense to say "if
>(!ptr)..."

This will also work in any valid C implementation.