bug#33275: 27.0.50; Image cache pruning

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: 33275@debbugs.gnu.org
> Date: Mon, 05 Nov 2018 20:06:41 +0100
> 
> In general, if you don't have a reference to an object, you can be
> pretty sure that Emacs is going to garbage-collect it.

Of course.  But you cannot control when that GC will happen.

> > That it doesn't is just sheer luck: the way we manage buffer memory is
> > special.  With any other Lisp object, it could well grow
> > uncontrollably.
> 
> What other non-referenced Lisp object can realistically make Emacs grow
> in this way?

Theoretically, anything.  In practice, I've seen such situations with
fonts.