Ephemerons, self-referentality in weak hashtables

[Christopher Lemmer Webber]

Hello,

I'm finally taking some time to port Goblins to Guile, in-between other
tasks anyway.  In Goblins there is a weak hashtable that maps current
actor references to their current behavior.  I found that for
self-referential actors, I needed ephemerons for GC stuff to work right.

In this old thread I found Wingo mentioning them:

Andy Wingo writes:

>   * If there is a possibility of a path from B to A, you need an
>     ephemeron table, and Guile doesn't do that right now.  But it
>     should!

Is there something ephemeron-like I should be doing?