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

From: Paul Pogonyshev <[email-masked]>
Date: Sat, 13 Oct 2018 13:38:11 +0200

OK, but why does it hit the limit? Logically, by the time cleanup form
is called, all the (overflow) stack frames should be removed and the
cleanup form should see practically empty stack. It shouldn't be much
different from calling cleanup without overflowing the stack to begin
with.

Paul
On Sat, 13 Oct 2018 at 13:30, Eli Zaretskii <[email-masked]> wrote:
>
> > Date: Sat, 13 Oct 2018 14:01:00 +0300
> > From: Eli Zaretskii <[email-masked]>
> > Cc: [email-masked]
> >
> > > 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).