Re: MPS: weak hash tables

[Eli Zaretskii <eliz@gnu.org>]

> From: Gerd Möllmann <gerd.moellmann@gmail.com>
> Cc: pipcet@protonmail.com,  eller.helmut@gmail.com,  yantar92@posteo.net,
>   emacs-devel@gnu.org
> Date: Sun, 07 Jul 2024 19:08:45 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > But does igc know that an interval is no longer needed?  How does it
> > know that when sweep_intervals in the old GC needed to do that
> > explicitly in C?
> 
> It's kind of mark-sweep vs. copying collector algorithms.
> 
> The mark phase of mark-sweep marks all objects reachable from roots,
> then the sweep phase frees what's not marked.
> 
> A copying collector copies every object reachable from roots. At the
> end, what has not been copied is implicitly unreachable.
> 
> MPS is a copying collection, with some additional complications, like
> ambiguous references (-> mostly-copying), and incrementality (->
> barriers), but the principle is still the same.

I understand all that, but unchaining an interval involves the need to
modify the pointers of its adjacent nodes, and how can MPS do that
without understanding our data structures?