bug#22149: 24.4; gdb stack overflow in regexp matcher

[Eli Zaretskii]

> From: Mattias Engdegård <mattiase@acm.org>
> Date: Sat, 14 Mar 2020 10:04:38 +0100
> Cc: Noam Postavsky <npostavs@gmail.com>, 22149-done@debbugs.gnu.org,
>         Andreas Schwab <schwab@suse.de>, Cheng-An Yang <rhymer123@gmail.com>
> 
> 14 mars 2020 kl. 08.58 skrev Eli Zaretskii <eliz@gnu.org>:
> 
> >  Moreover, we
> > might decide, for different reasons, to bump up the stack size of the
> > Emacs binary, which will indirectly fix this problem by making it less
> > probable.
> 
> I'm not sure how the C and regexp engine stacks relate to each other in 
> practice -- main() attempts to grow the C stack to accommodate the maximal 
> regexp stack, but SAFE_ALLOCA is set up to use the heap when necessary. 
> Surely we could decouple them more or less entirely, since the extra cost for 
> malloc is bound to be small when a lot of regexp stack is needed.

I think regex-emacs.c already overrides some of the SAFE_ALLOCA
machinery to that effect, does it not?