Re: using finalizers

[Tomas Hlavaty]

On Fri 31 Dec 2021 at 10:46, LdBeth <andpuke@foxmail.com> wrote:
>>>>>> In <878rw1pvcw.fsf@logand.com> Tomas Hlavaty <tom@logand.com> wrote:
> You are probably taking the wrong assumption about the effect of letrec
> So, `close' is nil and the lambda is never set as the finalizer.

You are right, the order was wrong.

>> What is the expected example usage of finalizers in Emacs Lisp?
>> How can I verify, that my finalizer works?
>
> (setq bar nil)
> (setq foo (make-finalizer (lambda () (setq bar t))))
> (setq foo nil)
> (garbage-collect)
> bar ; => t

Nice, that works.

One more question: Because make-finalizer in Emacs Lisp does not take
the object into account, I have to make sure to hold the reference to
the finalizer somehow.  However, this might not be trivial, because a
smart compiler could eliminate the reference.  Is this not an issue?
Shouldn't make-finalizer take the object as an argument and not rely on
me holding the reference explicitly?

Thank you!