Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!stanford.edu!neon.Stanford.EDU!kaufman
From: kaufman@neon.Stanford.EDU (Marc T. Kaufman)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Why won't ResError return the right message?
Message-ID: <1991May8.055136.27101@neon.Stanford.EDU>
Date: 8 May 91 05:51:36 GMT
References: <12946@pt.cs.cmu.edu> <1991May8.031012.1845@cbnewsk.att.com>
Organization: Computer Science Department, Stanford University, Ca , USA
Lines: 19

In article <1991May8.031012.1845@cbnewsk.att.com> ech@cbnewsk.att.com (ned.horvath) writes:
>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))
 
>- 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.

And just to make it worse, *handle won't be NULL for a purged resource,
but StripAddress(*handle) will be.  The purge and resource bits are still
on (at least in 24 bit memory models).

Finally: a use for StripAddress.

Marc Kaufman (kaufman@Neon.stanford.edu)