Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!wuarchive!mit-eddie!uw-beaver!ubc-cs!fornax!mcdonald
From: mcdonald@fornax.UUCP (Ken Mcdonald)
Newsgroups: comp.sys.mac.programmer
Subject: How to do garbage collection in C
Message-ID: <153@fornax.UUCP>
Date: 1 Dec 89 19:34:29 GMT
Organization: School of Computing Science, SFU, Burnaby, B.C. Canada
Lines: 24

I'm programming an applica[tion which has need of a built-in garbage
collector.  Specifically, I need a garbage collector that can allocate
arbitrarily-sized blocks, resize blocks, and do automatic reclamation of
unused blocks--I think that mark-scan reclamation is best for my purposed,
although if anyone knows of anything better, I'd appreciate hearing about
it.  (Note that I'm using the term "garbage collector" rather sloppily,
to include the dynamic memory allocator as well.)

Conceptually this is easy, I just use the Mac memory manager to allocate
a large block, and then do all of my own allocation in it.  The problem I'm
facing right now is in trying to program the reclamation algorithm in C--in
order to mark the unused blocks, I need to crawl along the stack, following
out any pointers that happen to have been pushed onto the stack.  This brings
up several problems, namely:  How to explicitly access C's stack; how to
differentiate pointers from other data; how to determine when the end of the
stack has been reached.  I'm a novice C programmer, and would appreciate
tips on these from people more skilled than myself.

On the other hand, if anyone happens to have a garbage collector just
lying around that would do everything I need, I wouldn't mind a copy of
that!
Thanks for all the help, netland . . .
Ken McDonald
{mcdonald@lccr.cs.sfu.ca}