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From: d88-jwa@dront.nada.kth.se (Jon W{tte)
Newsgroups: comp.sys.mac.programmer
Subject: Re: Double dereferenced handles
Message-ID: <1991Feb1.160826.19760@nada.kth.se>
Date: 1 Feb 91 16:08:26 GMT
References: <1991Jan30.215459.7730@umiami.ir.miami.edu>
Organization: Royal Institute of Technology, Stockholm, Sweden
Lines: 44

In article <> gv9b2c9z@umiami.ir.miami.edu (Ordinary Man) writes:

>Is it bad programming practice to double dereference a handle to a record

No, if it's only an assignment, I prefer this way.

>	HLock(Handle(theList));
>	temp:=theList^;
>	temp^.item:=whatever;

>	HLock(Handle(theList));
>	theList^^.item:=whatever;

>Or does it matter?

Not by much. If you don't like temp variables cluttering the
declarations, you know what way to go...
(Oh, and you mught be tempted to use the dereferenced handle
later if it's hanging around in a pointer...)

btw, you don't have to lock the handle if all you do with
it is assignment, AND THE R.H.S. EXPRESSION DOESN'T MOVE
MEMORY. Floating-point moves memory, as does trap calls.
Simple math doesn't move memory.

i.e.

	WindowRecord * * myWHandle = NewHandle ( sizeof ( WindowRecord ) ) ;

/* Error checking &c ... */

	* * myWHandle = * thePort ; /* This is legal without
					locking the handle ! */


>Thanks in advance,

You're welcome,

							h+
::::::::       Jon W{tte, Stockholm, Sweden, h+@nada.kth.se       ::::::::
"The IM-IV file manager chapter documents zillions of calls, all of which
seem to do almost the same thing and none of which seem to do what I want
them to do."  --  Juri Munkki (jmunkki@hut.fi) in comp.sys.mac.programmer