Re: [LONG] undo-tree and garbage collection: a request for advice from the gurus

[Stefan Monnier <monnier@iro.umontreal.ca>]

> I spent quite a lot of time re-implementing `undo-tree-mode' so that
> rather than transferring undo data out of `buffer-undo-list',
> `buffer-undo-tree' instead stored pointers to undo changesets in
> `buffer-undo-list'...only to eventually realise that this wasn't going to
> solve anything!

It'll work but only if your references into buffer-undo-list are weak
(i.e. they don't prevent the pointed elements from being GC'd).
For undo-equiv-table I do that by using a weak hash-table:

  (defconst undo-equiv-table (make-hash-table :test 'eq :weakness t)


-- Stefan