bug#7496: 23.2; copy recursive keymap cause crash

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: monnier@iro.umontreal.ca,  ari@mbf.ocn.ne.jp,  7496@debbugs.gnu.org
> Date: Sun, 13 Oct 2019 19:56:47 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > What happens in the current master without that limitation?  We have
> > since added stack overflow protection -- doesn't it kick in in this
> > case?
> 
> No, Emacs just crashes hard.  I haven't examined why, though -- I didn't
> know about the new stack overflow protection.

Maybe because the stack overflow happens during GC.