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bug#7496: 23.2; copy recursive keymap cause crash
From: |
Lars Ingebrigtsen |
Subject: |
bug#7496: 23.2; copy recursive keymap cause crash |
Date: |
Sun, 13 Oct 2019 03:15:17 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) |
Stefan Monnier <monnier@iro.umontreal.ca> writes:
>> When I call `copy-keymap' with a keymap which contains recursive binding,
>> the emacs crashed.
>> I can reproduce it by following sexp.
>
>> (let ((map (make-sparse-keymap)))
>> (define-key map " " map)
>> (copy-keymap map))
>
> I'm not surprised. There are many ways to address it:
> - try and make sure we better handle the "using up all memory" case
> rather than crashing. This is very difficult. We already try to do
> it, but clearly it's not working that well.
> - try and detect such cycles and either signal an error or reproduce the
> same cycle in the copy. We have added such things in several other
> cases, so we should probably do that.
While this is a pretty obscure, Emacs shouldn't crash on stuff like
this. I first considered whether just to check for EQ in Fcopy_keymap,
but it's possible to have nested keymaps that are mutually recursive,
so that won't work.
So I just added a recursion counter and refuse to copy when we've
reached level 100.
It does not protect against the case where the keymap is a char table
where one of the entries is the same keymap, but I don't know whether
that's a thing.
--
(domestic pets only, the antidote for overdose, milk.)
bloggy blog: http://lars.ingebrigtsen.no
- bug#7496: 23.2; copy recursive keymap cause crash,
Lars Ingebrigtsen <=