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From: guy@gorodish.UUCP
Newsgroups: comp.lang.c
Subject: Re: To comment 48: Xenix
Message-ID: <17441@sun.uucp>
Date: Mon, 27-Apr-87 14:45:22 EDT
Article-I.D.: sun.17441
Posted: Mon Apr 27 14:45:22 1987
Date-Received: Wed, 29-Apr-87 00:48:13 EDT
References: <77200001@uiucdcsp>
Sender: news@sun.uucp
Reply-To: guy@sun.UUCP (Guy Harris)
Organization: Sun Microsystems, Mountain View
Lines: 52

>But I think that declaring:
>
>#define NULL (char *)0
>
>is expensive but will always do the trick for all models (small,large,huge)

And will also tick "lint" (and PCC, in some cases, I suspect) with
some justification.

>On UNIX System V AT I had done the typical tricks in C of:
>
>   if (!charptr)
>
>   Even though I new it was crypt, but efficient.

If

	if (!charptr)

is any more efficient than

	if (charptr == 0)

you have some justification for flaming the author(s) of your
compiler.  The two constructs are equivalent, and any good compiler
will produce equally efficient code for them.

>   So after alot of frustration I figured out that NULL was defined
>   as 0L. Which makes sense since we need a 32 bit zero value, which
>   is not an integer.

No, it makes no sense whatsoever because:

	1) a 32-bit zero value *is* an integer; it just doesn't
	happen to be an "int";

and

	2) "we" don't need a 32-bit zero value, we need a null
	pointer of the appropriate type, and null pointers are not
	integers.

>   But As for people saying that if (charptr == 0) should work,
>   "for any good C programmer's" I think thats hogwash.

Anyone who knows the C language well enough to make their comments on
this newsgroup worth believing knows that

	if (charptr == 0)

should work.  Anyone who knows the C language well enough that they
should feel competent to implement it knows that it should work.