bug#33034: `unwind-protect' cleanup form is not executed if body dies in stack overflow

[Eli Zaretskii]

> Date: Sat, 13 Oct 2018 14:01:00 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 33034@debbugs.gnu.org
> 
> > I haven't looked into the source code, but it seems that these
> > examples don't involve C-level stack overflow.
> 
> You are right, this issue is unrelated to C stack overflow.

What actually happens here is that the cleanup form _is_ called, but
it again hits the limit of Lisp local bindings, and therefore itself
signals an error.  And unwind-protect does not protect cleanup forms
(this is documented).