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From: d88-jwa@byse.nada.kth.se (Jon W{tte)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Why won't ResError return the right message?
Message-ID: <D88-JWA.91May9134756@byse.nada.kth.se>
Date: 9 May 91 11:47:59 GMT
References: <1696@babcock.cerc.wvu.wvnet.edu>
	<1991May6.143630.30448@kuhub.cc.ukans.edu> <13382@goofy.Apple.COM>
	<12946@pt.cs.cmu.edu> <13404@goofy.Apple.COM>
Sender: news@nada.kth.se (Mr News)
Organization: Royal Institute of Technology, Stockholm, Sweden
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In-reply-to: REEKES@applelink.apple.com's message of 8 May 91 17:56:31 GMT

In article <13404@goofy.Apple.COM> REEKES@applelink.apple.com (Jim Reekes) writes:

   > #define goodHand(x)    ((x) && *(x))

   A problem with goodHand above is that if the GetResource fails, then you
   may end up dereferencing a nil address.  It will happen with Pascal's
   AND expression, but not with MPW Pascal's &.  It all depends on the
   language's implementation.  It's safe to just check on the handle

Well, the example was in C, and C structly specifies lazy evaluation
of logical expressions (like &&)

   unless you set ResLoad to false and the resource isn't in memory.  BUT...
   if you set ResLoad to false (which is a valid thing to do) then goodHand
   above will always report an error!

If you call SetResLoad(false) you probably know what you do, it's
not a call to call lightly (and certain portions of the OS & toolbox
will fail with SetResLoad(false))

--
						Jon W{tte
						h+@nada.kth.se
						- Power !