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From: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer)
Newsgroups: comp.sys.amiga
Subject: Re: Manx C
Message-ID: <4595@jade.BERKELEY.EDU>
Date: Wed, 5-Aug-87 03:26:07 EDT
Article-I.D.: jade.4595
Posted: Wed Aug  5 03:26:07 1987
Date-Received: Fri, 7-Aug-87 06:50:52 EDT
References: <4028@spool.WISC.EDU> <4540@jade.BERKELEY.EDU> <1836@vax135.UUCP>
Sender: usenet@jade.BERKELEY.EDU
Reply-To: mwm@eris.BERKELEY.EDU (Mike (My watch has windows) Meyer)
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In article <1836@vax135.UUCP> cjp@vax135.UUCP (Charles Poirier) writes:
<This has been posted before but it may need to be said again.
<The problem Mike Meyer mentioned, about Manx C claiming illegal
<pointer-to-int comparison in
<
<if (ptr == NULL)
<
<can be fixed by redefining NULL.  As in:
<
<#undef NULL
<#define NULL ((void *) 0L)
<
<The cast of "pointer to void" tells the compiler to "ignore pointer type".
<You might want to go and change the include file which (mis)defined NULL
<in the first place.  I misrecall which file that is, sorry.

Uh, when you start talking about "misdefining NULL", you're walking on
very thin ice. K & R are noticably silent, except to say that
"assigning a constant 0 to a pointer will produce a null pointer
distinguished from a pointer to any object."

dpANS says that NULL must be defined, and must be either "0" or
"((void *) 0))". *Not* "0L". Making it 0L creates a whole different
set of headaches.

So I'd claim that you're misdefining NULL to cover for a bug in the
compiler.

Of course, "if (ptr == 0)" is as valid as "if (ptr == NULL)", and
probably isn't fixed by that change. That the identical "if (!ptr)"
doesn't produce an error message may indicate that "if (ptr == 0)"
won't, either.

	<mike
--
ICUROK2C, ICUROK2.				Mike Meyer
ICUROK2C, ICWR2.				mwm@berkeley.edu
URAQT, I WANT U2.				ucbvax!mwm
OO2EZ, I WANT U2.				mwm@ucbjade.BITNET