Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!mailrus!cornell!uw-beaver!tektronix!tekcrl!tekgvs!jans
From: jans@tekgvs.GVS.TEK.COM (Jan Steinman)
Newsgroups: comp.lang.smalltalk
Subject: Re: Unwanted Instances
Message-ID: <4157@tekgvs.GVS.TEK.COM>
Date: 27 Oct 88 19:11:47 GMT
Distribution: na
Organization: Tektronix Inc., Beaverton, Or.
Lines: 22

<If anyone has any tried-n-true heuristics for chiseling an obnoxious object 
loose from an image, I'd sure like to hear about it.>

I don't have a quick answer, but there are ways of avoiding generating 
"obnoxious objects" in the first place.  Any object that is potentially 
circular (which includes any object that stores BlockContexts) should implement 
"release", which should always include "super release".  "release" should nil 
the fields that contain BlockContexts or could be circular.  (If you're 
dredging up MethodContexts, your obnoxious object probably references 
BlockContexts.)

The need to store BlockContexts is a real problem, but avoiding direct 
circularities is a bit easier to deal with.  The reasons circular objects are 
created can often be fulfilled by judicious use of "thisContext", which is the 
execution state of a particular method.  (C++er's drool!  You'll never do 
this!)  I've implemented a number of methods for detecting recursion and 
carrying on a dialog with a sender, and I find I can often use these instead of 
creating circular references.

:::::: Software Productivity Technologies -- Experiment Manager Project ::::::
:::::: Jan Steinman N7JDB	Box 500, MS 50-383	(w)503/627-5881 ::::::
:::::: jans@tekcrl.TEK.COM	Beaverton, OR 97077	(h)503/657-7703 ::::::