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From: pratt@csn.org (Jonathan Pratt)
Subject: Re: Why won't ResError return the right message?
Message-ID: <1991May9.040511.26710@colorado.edu>
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Organization: University of Colorado Boulder, OCS
References: <12946@pt.cs.cmu.edu> <1991May8.031012.1845@cbnewsk.att.com> <1991May8.055136.27101@neon.Stanford.EDU>
Date: Thu, 9 May 1991 04:05:11 GMT
Lines: 30

In article <1991May8.055136.27101@neon.Stanford.EDU> kaufman@neon.Stanford.EDU (Marc T. Kaufman) writes:
>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))
> 
>
>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).
>
Come on.  Programming the Mac is enough work without this kind of dis-
information.  Next time get a reference.  From Inside Mac:

	Before attempting to access any purgeable block, you must
	check its handle to make sure the block is still allocated.
	If the handle is empty (that is, h^ = NIL, where h is the
	handle), then the block has been purged; ...

Last I heard, NIL still means zero. :-)

Jonathan

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