Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!uwm.edu!lll-winken!decwrl!shlump.nac.dec.com!ashok.dec.com!nadkarni
From: nadkarni@ashok.dec.com
Newsgroups: comp.lang.c++
Subject: distinguishing stack/heap, garbage collection
Message-ID: <9084@shlump.nac.dec.com>
Date: 11 Mar 90 19:54:10 GMT
Sender: newsdaemon@shlump.nac.dec.com
Organization: Digital Equipment Corporation
Lines: 24


I'm just learning C++ so maybe I'm missing something obvious. How do you
distinguish between class objects allocated on the stack or static store 
and those allocated on the heap ? I have an application that would benefit 
greatly from garbage collection. Plenty of circular links so reference
count based GC is out. Stop-and-collect is acceptable so I was planning
on a simple mark and sweep scheme. However, I can't figure out a way to locate
the `roots' (stack/static store) and distinguish them from the GC-able
objects. One way might be to overload the new operator for GC classes so
that you keep a list of the addresses of such objects and use this list to
check if a object is in the heap or not (kind of like Boehm's GC, which
I cannot use for some other reasons). But it seems like this check would
be too much overhead even for my (so what if it's slow) application. Unless
there is a way of telling in a constructor whether the object is allocated
on the stack or not and then remembering that info in a tag. Is this possible ?

As a related request, someone mentioned a C++ garbage collector (not Bartlett's
and not Boehm's) a little while ago. I think it was part of some package
(EC++ perhaps?). Since I do not have ftp access, could some kind soul mail
it (just the GC part) to me if it is not too big ? Thanks,

/Ashok Nadkarni
Digital Equipment Corp.
Standard disclaimer applies.