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From: Eli Zaretskii <eliz@gnu.org>
To: npostavs@users.sourceforge.net
Cc: 24751@debbugs.gnu.org
Subject: bug#24751: 26.0.50; Regex stack overflow not detected properly (gets "Variable binding depth exceeds max-specpdl-size")
Date: Tue, 15 Nov 2016 18:12:09 +0200	[thread overview]
Message-ID: <83d1hwhgdi.fsf@gnu.org> (raw)
In-Reply-To: <87wpg5l9st.fsf@users.sourceforge.net> (npostavs@users.sourceforge.net)

> From: npostavs@users.sourceforge.net
> Cc: 24751@debbugs.gnu.org
> Date: Mon, 14 Nov 2016 22:08:18 -0500
> 
> Actually, we should avoid increasing this limit if the stack wasn't
> increased, right?  Here's what I came up with, I think it doesn't cover
> Cygwin/Windows though.
> 
> diff --git c/src/emacs.c i/src/emacs.c
> index b74df21..d4655c8 100644
> --- c/src/emacs.c
> +++ i/src/emacs.c
> @@ -831,8 +831,8 @@ main (int argc, char **argv)
>  	 re_max_failures, then add 33% to cover the size of the
>  	 smaller stacks that regex.c successively allocates and
>  	 discards on its way to the maximum.  */
> -      int ratio = 20 * sizeof (char *);
> -      ratio += ratio / 3;
> +      int min_ratio = 20 * sizeof (char *);
> +      int ratio = min_ratio + min_ratio / 3;
>  
>        /* Extra space to cover what we're likely to use for other reasons.  */
>        int extra = 200000;
> @@ -869,6 +869,7 @@ main (int argc, char **argv)
>  
>        /* Don't let regex.c overflow the stack.  */
>        re_max_failures = lim < extra ? 0 : min (lim - extra, SIZE_MAX) / ratio;
> +      emacs_re_safe_alloca = re_max_failures * min_ratio;
>      }
>  #endif /* HAVE_SETRLIMIT and RLIMIT_STACK and not CYGWIN */

Right, but I have 2 comments:

  . we shouldn't set re_max_failures to zero if the amount of stack is
    less than 'extra', since in that case we will allocate the failure
    stack off the heap;
  . emacs_re_safe_alloca should have its minimum value MAX_ALLOCA, not
    zero, because SAFE_ALLOCA can still be used in regex.c, even
    though the failure stack will be malloc'ed.

Thanks.





  reply	other threads:[~2016-11-15 16:12 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-10-21  3:54 bug#24751: 26.0.50; Regex stack overflow not detected properly (gets "Variable binding depth exceeds max-specpdl-size") npostavs
2016-11-04  8:22 ` Eli Zaretskii
2016-11-05 19:34   ` npostavs
2016-11-06 15:45     ` Eli Zaretskii
2016-11-13  5:39       ` npostavs
2016-11-13 16:12         ` Eli Zaretskii
2016-11-15  3:08           ` npostavs
2016-11-15 16:12             ` Eli Zaretskii [this message]
2016-11-16  1:06               ` npostavs
2016-11-16 16:25                 ` Eli Zaretskii
2016-11-16 23:25                   ` npostavs
2016-11-17 16:21                     ` Eli Zaretskii
2016-11-19 10:02                       ` Eli Zaretskii
2017-01-01 18:33                       ` npostavs
2017-01-01 18:41                         ` Eli Zaretskii
2017-01-01 18:57                           ` npostavs
2017-01-01 20:06                             ` Eli Zaretskii
2017-01-02  4:49                       ` npostavs
2017-01-02 15:24                         ` Eli Zaretskii
2017-01-02 18:30                           ` npostavs
2017-01-02 19:22                             ` Eli Zaretskii
2017-01-08 23:49                               ` npostavs

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