Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!usc!cs.utexas.edu!uunet!mcvax!kth!draken!tut!tucos!moj
From: moj@cs.utu.fi (Matti Jokinen)
Newsgroups: comp.lang.clu
Subject: Re: Garbage collection and types.
Message-ID: <908@tucos.UUCP>
Date: 20 Jun 89 21:52:25 GMT
References: <788@scaup.cl.cam.ac.uk>
Reply-To: moj@utu.fi (Matti Jokinen)
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Organization: University of Turku, Finland
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Approved: moj@cs.utu.fi
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References to related work:

%A Atkins, Martin C.
%A Nackman, Lee R.
%T The Active Deallocation of Objects in Object-Oriented Systems
%J Software - Practice & Experience
%V 18
%N 11
%P 1073-1089
%D Nov 1988
%X In object-oriented systems, it is often useful for objects to be allowed to
carry out some action before they are deallocated.  This can be done by
defining a destroy method in the object's class, and arranging for the memory
system to send a message invoking this method immediately before deallocating
the object.  This allows resources associated with the object to be returned
to the system, limited cross-language garbage collection, and other, more
complex, behaviour.  During the execution of the destroy method it is possible
for new references to objects to be created.  Care must be taken that the
garbage collector does not erroneously free such objects.  Algorithms are
presented to implement destroy methods in systems using reference counting and
mark-scan garbage collection techniques.  Preperties that are desirable in such
systems are also discussed.

%A Jokinen, Matti O.
%T Customizable Garbage Collectors
%J Information Processing Letters
%V 30
%N 3
%D 13 Feb 1989
%P 115-118
%X Conventional garbage collectors retain components of data structures as long
as the structure itself is accessible.  In some applications, however, the
components of a data structure are useful only if they are referred by
external pointers.  Recognition and deletion of useless components requires
co-operation between the garbage collector and the user program: the analysis
of accessibility is carried out by the garbage collector but user-defined
routines are necessary to remove obsolete components from the structure.  Two
different co-operation mechanisms are discussed; the first can be used with
garbage collectors based on reference counters, the other with mark-and-sweep
collectors.