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From: thomasw@hpcupt1.cup.hp.com (Thomas Wang)
Newsgroups: comp.lang.c++
Subject: Re: garbage collection and member functions
Message-ID: <7050038@hpcupt1.cup.hp.com>
Date: 20 Dec 90 19:07:10 GMT
References: <1990Dec20.045909.7681@rice.edu>
Organization: Hewlett Packard, Cupertino
Lines: 43

/ hpcupt1:comp.lang.c++ / dougm@zamenhof.rice.edu (Doug Moore) /  8:59 pm  Dec 19, 1990 /

>Please give a thought to the following problem if garbage collection
>interests you.  Otherwise, skip it.

> The implementation as it stands allocates new Conses regularly, and
> most of them become garbage; I desire to add a copy-collect garbage
> collector, to better control memory usage.  In order to avoid
> rewriting all my code, I choose to overload operator new for Conses,
> so that it copies and collects when a call for a new Cons cannot be
> immediately satisfied.

> But this blows my member functions all to hell.

This is a known problem with C++.  Copy collector does not work, because
of the passing of 'this' pointer.

Only way for copying collector to work for C++ is to change the compiler.

Precise collector without supporting multiple inheritance can be implemented
without changing the compiler.  I did the implementation as a master thesis,
so this might not be a good class assignment.

Conservative collectors are always available though.  You can get Boehm's
collector via anonymous FTP.

> In case you wondered, this was a school assignment.  I was the
> assigner, not an assignee, and I'm beginning to wonder if it is an
> appropriate assignment in light of the ugliness of any solution I can
> find.

Most straight forward thing I can think of is to use reference counting.
It's only a class assignment, so kludgy solution should be fine.  Or even
don't delete any memory!  As long as the program don't run too long, the
program should run fine.

>Doug Moore


 -Thomas Wang
              (Everything is an object.)
                                                     wang@hpdmsjlm.cup.hp.com
                                                     thomasw@hpcupt1.cup.hp.com