I didn't read the docs very well. I understand that I have to mark
every object as needing finalization with call_finalizer(anObject) (BTW
the example in the RubyCentral lib reference does not seem to be
complete).

Is there any way I can mark all objects belonging to a certain class as
needing finalization? (I guess I could walk through all objects (from the 
class) in the ObjectSpace and mark them but this seems cumbersome...)

It could be really useful to have

ObjectSpace.call_finalizer_for_classes([aClassOrMod])

if it's not in there. What do you think?

Regards,

Robert