Name: rm29839 Date: 03/17/98

=20
The current specification of when the finalize
methods are run is insufficient for handling
other resources than memory. I belive this is
important and has to be fixed.

The following illustrates how it can be done
independent of the current garbage collection
mechanism and without changing the VM.

The compiler can recognize that a class has a
finalize method. Each reference to such a class
is specially handled. The compiler simply places
code for handling a reference count hidden in
objects of classes that has a finalize method.
Assignment and the reference going out of scope
is handled especially, and the object's finalize
method is run when the reference count becomes
zero.

We may assume that the finalize method is
sparingly used, and the inefficiency of the extra
code for each assignment of these references are
well worth taking.=20

The garbage collecting can be largly left unchanged
and may be implemented with unimpared efficiency.
One change though. we don't want the finalize
methods to be run more than once. The garbage
collection should therefore not run them,
except for when the reference count is different
from zero.

I don't belive this scheme would require any change
to the virtual machine. The compiler does all the
work by laying out extra code for the finalize
references. The extra reference count field in
these objects should not be visible to the VM.

I don't want to tag the special references in any
way such as "finalize" or "runFinalization")
because this would be percieved as a complication
of the language.
The only reason for such a tag would be if we
belive that the finalize method is commonly used
when the finalization can be delayed to when
garbage collection is made.=20

I don't belive these ideas are very original, but
perhaps worth pointing out anyway. I myself didn't
realize at once how simple it would be to get this
replacement for the C++ destructor.
(Review ID: 26297)
======================================================================