Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!mcsun!tuvie!vmars!hp
From: hp@vmars.tuwien.ac.at (Peter Holzer)
Newsgroups: comp.lang.c
Subject: Re: Using Macros
Message-ID: <1752@tuvie>
Date: 9 Aug 90 16:23:55 GMT
References: <362.26be9dcc@astro.pc.ab.com> <21057@grebyn.com> <642@travis.csd.harris.com> <17298@haddock.ima.isc.com> <46860@brunix.UUCP> <10881@crdgw1.crd.ge.com>
Sender: news@tuvie
Lines: 38

volpe@underdog.crd.ge.com (Christopher R Volpe) writes:

>In article <46860@brunix.UUCP>, gvr@cs.brown.edu (George V. Reilly) writes:
>|>Ah, but Karl, you missed the more important bug that Brad should have
>|>used &&, not ||.  In Brad's example, exit() will only be called if
>|>cond == 0, which is exactly the inverse of what is desired.  The same is
>|>true of your second offering.

>What makes you think that is what was desired? I interpret "CHECK(cond)"
>the same way I interpret "ASSERT(cond)", which is "continue iff cond is true".
>I.e., exit when cond is false. Under this interpretation, "||" is correct.

What made ME think that this s what was desired is this line in the original 
posting:
From: brad@SSD.CSD.HARRIS.COM (Brad Appleton)
> 
> 	#define CHECK(cond)  { if (cond)  exit(-1);  }
> 
which is certainly not equivalent to:
> 
> 	#define CHECK(cond)  ((cond) || exit(-1))
> 
but to
#define CHECK(cond)  ((cond) && exit(-1))

Karl obviously interpreted it the same way or he would not have
suggested:

From: karl@haddock.ima.isc.com (Karl Heuer)
>	#define CHECK(cond)  ((cond) ? exit(-1) : (void)0)

It is amazing though, that the Walking Lint missed the ||-&& confusion.
Oh well, the program would miss it too :-)
--
|    _	| Peter J. Holzer			| Think of it	|
| |_|_)	| Technische Universitaet Wien		| as evolution	|
| | |	| hp@vmars.tuwien.ac.at			| in action!	|
| __/  	| ...!uunet!mcsun!tuvie!vmars!hp	|     Tony Rand	|