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From: ech@cbnewsk.att.com (ned.horvath)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Why won't ResError return the right message?
Message-ID: <1991May8.031012.1845@cbnewsk.att.com>
Date: 8 May 91 03:10:12 GMT
References: <12946@pt.cs.cmu.edu>
Organization: AT&T Bell Laboratories
Lines: 27

From article <12946@pt.cs.cmu.edu>, by hairston@henry.ece.cmu.edu (David Hairston):

> there's a no-brainer which has worked its way into my code (C example):

> #define goodHand(x)    ((x) && *(x))
> 
> which gets used for:
> 
> realHandle = GetResource(type, index);
> if (!goodHand(realHandle))
>     ....

Your no-brainer misses two potential problems:

- if I call it with, say, "goodHand (myH++)" (or any other expression
with side-effects) things get ugly (and VERY hard to debug!).

- there is a distinction between handle==NULL and *handle==NULL for
resources: a NULL handle either doesn't exist or hasn't been initialized,
whereas a non-null resource handle which dereferences to a NULL indicates
a purged resource -- call LoadResource to pull the data in.

=Ned Horvath=
-- 

=Ned Horvath=
ehorvath@attmail.com