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Re: gc and deallocation

At 10:15 AM 94.01.05 -0500, Thomas A. Russ wrote:
>In article <...> bill@cambridge.apple.com (Bill St. Clair) writes:
> > At 10:40 PM 1/4/94 -0500, Robert Bruce Findler wrote:
> >>What happens to memory that is allocated in a clos object when the
> >>object is gc'ed? Is there a method that should be defined to clean-up
> >>after the object? Some sort of deallocate-instance?
> >
> > When a CLOS object is garbage collected, it's memory is freed for reuse.
> > The memory of the objects in its slots will also be freed if those objects
> > are not referenced by any other live objects. MCL's garbage collector
> > does not support an explicit user-specifiable clean-up procedure.
> > You normally don't need one, though some applications, e.g. persistent
> > object databases, can benefit from such a feature.
> >
>I would imagine that if you have pointers into the Macintosh heap that
>were stored in the CLOS object you would end up with a memory leak if
>you didn't have some disposal routine of your own.  If you do this, then
>you will need to explicitly deallocate the Macintosh heap memory.

In our OODB we have used a MCL feature...

(eval-when (:compile-toplevel :execute)
  (require "LAPMACROS"))

(defun new-gcable-handle (size)
  (let ((h (#_newhandle size)))
    (when (%null-ptr-p h)
      (setq h (#_newhandle size)))
    (if (%null-ptr-p h)
      (%setf-macptr (ccl::make-gcable-macptr ccl::$flags_DisposHandle) h))))

Handles created by new-gcable-handle in the Mac heap are gc'd just like
LISP heap objects.

I assume, since it's undocumented, that Apple does not sanction this for
general use or imply future support [Bill?].