Re: Garbage collect and buffer-undo-list

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

> I know the garbage collector trims buffer-undo-list. Does it collect the
> cons cell if there are other references to that object (other than
> buffer-undo-list)?

No, it can't.

If you want to keep a reference to some of those cons-cells but still
want the GC to collect them when the undo-log is trimmed, then you need
to use a weak reference.  We don't currently have plain "weak
references" in ELisp, but we do have hash-tables whose keys and/or
values can be weak references (that's what I used in
`undo-equiv-table`).


        Stefan