Subject: bug#33275: 27.0.50; Image cache pruning

From: Lars Ingebrigtsen <[email-masked]>
Date: Mon, 05 Nov 2018 20:06:41 +0100

Eli Zaretskii <[email-masked]> writes:

>> It would be reasonable if the code had asked for those images to be kept
>> in memory, but it hasn't.  Emacs decides that on its own without saying
>> that it's doing that.
>
> You cannot assume anything about memory management while a Lisp
> program runs.

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.  If you can't
assume that, then programming in Emacs Lisp becomes impossible.

Fortunately that's not the case, and programming in Emacs Lisp is nice
and easy.

>> It'd be similarly surprising if
>> 
>> (dolist (file (directory-files "/directory/with/many/images" t "png$"))
>>   (with-temp-buffer
>>     (insert-file-contents-literally file)))
>> 
>> were to lead to Emacs growing uncontrollably.
>
> 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?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no