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

[Eli Zaretskii]

> From: Steve Kemp <steve@steve.org.uk>
> Date: Thu, 06 Jul 2017 15:33:42 +0000
> 
>   In short your initial response to this particular case seems
>  like it would apply to any similar issue which  is liable to
>  be discovered - they'd be genuine bugs, but they'd also be things
>  that would never happen "in the wild", so while they wouldn't
>  be ignored, it would be easy to push them to the back of the queue.

That wasn't my intent, and I apologize if my wording somehow implied
that.  I was only talking about the particular crash you reported.
Any other crash should be analyzed separately, and the conclusion
could very well be different.

>   THanks.  I'm sitting on a couple of hundred crashing cases, just
>  trying to simplify them and see if they share the same cause (they
>  probably do).

Well, I hope some of them are for different reasons.

It is strange you cannot trigger the stack-overflow protection in your
build, though.  If you write a trivial infinite-recursion Lisp
function, and then run it after lifting max-lisp-eval-depth and
max-specpdl-size to the largest positive number, don't you see what I
saw on my system?