GNU bug report logs - #16999
calc crashes when computation limit is increased

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From: Dmitry Antipov <dmantipov <at> yandex.ru>
To: jay.p.belanger <at> gmail.com, Florian Beck <fb <at> miszellen.de>
Cc: 16999 <at> debbugs.gnu.org
Subject: bug#16999: calc crashes when computation limit is increased
Date: Thu, 13 Mar 2014 09:13:54 +0400

On 03/13/2014 02:44 AM, Jay Belanger wrote:

> This seems to be an Emacs problem, rather than a problem specific to Calc.
> Typing M doubles the sizes of `max-lisp-eval-depth' and
> `max-specpdl-size'.  Having  `max-lisp-eval-depth' equal to 64000 by
> itself doesn't seem to cause problems, but having `max-lisp-eval-depth'
> equal to 64000 and `max-specpdl-size' equal to 83200 does cause Emacs to
> crash on an infinite loop; evaluating:
>
>    (setq max-specpdl-size 83200
>          max-lisp-eval-depth 64000)
>
>    (defun f ()
>       (f))
>
>    (f)
>
> will crash Emacs.

This is C stack overflow (try to attach gdb and do 'bt' on crash). On
*NIX system, 'ulimit -s' shows your current limit.

Perhaps there should be a kind of protection against this. For example,
eval_sub can check current stack depth against getrlimit (RLIMIT_STACK,...).

Dmitry

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