bug#27585: segfault when evaluating a file containing only backticks

[Eli Zaretskii]

> From: Andreas Schwab <schwab@suse.de>
> Cc: Steve Kemp <steve@steve.org.uk>,  27585@debbugs.gnu.org
> Date: Thu, 06 Jul 2017 08:46:14 +0200
> 
> On Jul 05 2017, Eli Zaretskii <eliz@gnu.org> wrote:
> 
> > You wrote a program that triggers infinite recursion.
> 
> This isn't infinite recursion since the input is finite.

If we want to be pedantically accurate, then no "infinite" recursion
is ever truly infinite, since it will always stop when the system is
shut down, or the power fails, or the world ends, whichever happens
first.

So we are actually always talking about recursions deep enough to blow
up the stack.