Re: Collecting markers with MPS

[Gerd Möllmann]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Gerd Möllmann <gerd.moellmann@gmail.com>
>> Cc: Helmut Eller <eller.helmut@gmail.com>,  emacs-devel@gnu.org
>> Date: Wed, 24 Apr 2024 12:58:23 +0200
>> 
>> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
>> 
>> > Eli Zaretskii <eliz@gnu.org> writes:
>> >
>> >> Can't the new GC tell us which markers are unreferenced?
>> >
>> > I'm afraid no. At least I haven't seen it mentioned in the docs.
>
> Does this mean MPS doesn't allow a user-defined function to be called
> when some object is found unreferenced?  I'd assume such callbacks are
> available, since some objects need custom code to dispose of.

I think you mean finalization, which is supported, and implemented in
igc.

(MPS puts a finalization message on a message queue, which the client
processes when it wants. It can then call xfree malloc'd memory,
,unload compilation units etc.)

>> Err, and the marker would be references from the list anyway...
>
> Maybe I don't understand the problem we are talking about.  Is this
> about unchain_dead_markers, which is called from sweep_buffers?  If
> so, how are non-dead markers currently identified during the mark
> phase?

I'll better leave that Helmut to answer, he probably knows that better
than me, at the moment. Finalization of markers would not happen,
because the list it is in keeps it alive.