From: npostavs@users.sourceforge.net
To: peder@klingenberg.no (Peder O. Klingenberg)
Cc: 24358@debbugs.gnu.org
Subject: bug#24358: 25.1.50; re-search-forward errors with "Variable binding depth exceeds max-specpdl-size"
Date: Sat, 03 Sep 2016 11:43:16 -0400 [thread overview]
Message-ID: <87eg51ng4r.fsf_-_@users.sourceforge.net> (raw)
In-Reply-To: <87twe6sx2g.fsf@users.sourceforge.net> (npostavs@users.sourceforge.net's message of "Fri, 26 Aug 2016 23:35:51 -0400")
# this cloned bug doesn't have a patch yet
tags 24358 - patch
quit
npostavs@users.sourceforge.net writes:
> (I'm also on GNU/Linux, Arch) I get the same max-specpdl-size error with
> 25.1.50, with 24.5 (and below) I get (error "Stack overflow in regexp
> matcher")
The problem is that re_max_failures is set to 40001 (instead of the
original 40000) in main()[1], which is a problem because of the
GROW_FAIL_STACK uses (re_max_failures * TYPICAL_FAILURE_SIZE) as a cap
on the amount to allocate, but ((fail_stack).size * sizeof
(fail_stack_elt_t)) to calculate current allocation.
Since TYPICAL_FAILURE_SIZE = 20 and sizeof (fail_stack_elt_t) = 8, and
it seems that (fail_stack).size grows in increments of 3, when
(fail_stack).avail is 99999 and (fail_stack).size reaches 100002:
(fail_stack).size * sizeof (fail_stack_elt_t) => 800016
re_max_failures * TYPICAL_FAILURE_SIZE => 800020
ENSURE_FAIL_STACK(3) then loops indefinitely reallocating a stack of
size 800020 again and again until the record_xmalloc fails to
grow_specdl() (thus the "max-specpdl-size" error).
----------
So we we might want to fix the re_max_failures setting in main, but it
doesn't quite make sense to me that GROW_FAIL_STACK relies on
re_max_failures being a multiple of (sizeof (fail_stack_elt_t)). At the
definition of TYPICAL_FAILURE_SIZE we have
/* Estimate the size of data pushed by a typical failure stack entry.
An estimate is all we need, because all we use this for
is to choose a limit for how big to make the failure stack. */
/* BEWARE, the value `20' is hard-coded in emacs.c:main(). */
#define TYPICAL_FAILURE_SIZE 20
Why do we use an "estimate" here? What's wrong with just using
(re_max_failures * sizeof (fail_stack_elt_t)) as the limit? Or should
the limit actually be (re_max_failures * TYPICAL_FAILURE_SIZE * sizeof
(fail_stack_elt_t))?
-----------
827 long lim = rlim.rlim_cur;
(gdb) p rlim
$1 = {
rlim_cur = 8388608,
rlim_max = 18446744073709551615
}
(gdb) next
833 int ratio = 20 * sizeof (char *);
(gdb)
834 ratio += ratio / 3;
(gdb)
837 int extra = 200000;
(gdb) p ratio
$2 = 213
[...]
(gdb) display ((newlim - extra) / ratio)
1: ((newlim - extra) / ratio) = 40000
(gdb) next
856 newlim += pagesize - 1;
1: ((newlim - extra) / ratio) = 40000
(gdb)
857 if (0 <= rlim.rlim_max && rlim.rlim_max < newlim)
1: ((newlim - extra) / ratio) = 40019
(gdb)
859 newlim -= newlim % pagesize;
1: ((newlim - extra) / ratio) = 40019
(gdb)
861 if (pagesize <= newlim - lim)
1: ((newlim - extra) / ratio) = 40001
(gdb) undisplay 1
(gdb) next
863 rlim.rlim_cur = newlim;
(gdb)
864 if (setrlimit (RLIMIT_STACK, &rlim) == 0)
(gdb)
865 lim = newlim;
(gdb)
870 re_max_failures = lim < extra ? 0 : min (lim - extra, SIZE_MAX) / ratio;
(gdb)
875 stack_bottom = &stack_bottom_variable;
(gdb) p re_max_failures
$3 = 40001
-----------
[1]: This was the case since 9d356f62 2016-05-27 "Robustify stack-size calculation"
next prev parent reply other threads:[~2016-09-03 15:43 UTC|newest]
Thread overview: 76+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-26 20:17 bug#24315: 25.1.50; re-search-forward errors with "Variable binding depth exceeds max-specpdl-size" Peder O. Klingenberg
2016-08-27 3:35 ` npostavs
2016-08-30 13:09 ` Peder O. Klingenberg
2016-09-02 1:58 ` npostavs
2016-09-02 13:45 ` Peder O. Klingenberg
2016-09-03 14:21 ` npostavs
2016-09-06 8:18 ` Peder O. Klingenberg
2016-09-07 23:27 ` npostavs
2016-09-03 15:43 ` npostavs [this message]
2016-10-08 0:29 ` bug#24358: " npostavs
2016-10-08 5:55 ` Eli Zaretskii
2016-10-08 13:45 ` npostavs
2016-10-08 14:39 ` Eli Zaretskii
2016-10-08 14:47 ` Eli Zaretskii
2016-10-08 16:57 ` npostavs
2016-10-08 17:23 ` Eli Zaretskii
2016-10-08 18:52 ` npostavs
2016-10-08 19:47 ` Eli Zaretskii
2016-10-08 20:55 ` npostavs
2016-10-09 6:52 ` Eli Zaretskii
2016-10-13 1:29 ` npostavs
2016-10-13 6:19 ` Eli Zaretskii
2016-10-14 2:19 ` npostavs
2016-10-14 7:02 ` Eli Zaretskii
2016-10-19 3:11 ` npostavs
2016-10-19 7:02 ` Eli Zaretskii
2016-10-19 12:29 ` npostavs
2016-10-19 14:37 ` Eli Zaretskii
2016-10-20 4:31 ` npostavs
2016-10-20 8:39 ` Eli Zaretskii
2016-10-21 1:22 ` npostavs
2016-10-21 7:17 ` Eli Zaretskii
2016-10-22 2:36 ` npostavs
2016-10-22 21:54 ` Sam Halliday
2016-10-22 22:46 ` npostavs
2016-10-23 6:41 ` Eli Zaretskii
2016-10-23 8:57 ` Sam Halliday
2016-10-23 9:19 ` Eli Zaretskii
2016-10-23 13:40 ` Sam Halliday
2016-10-23 14:07 ` Eli Zaretskii
2016-10-23 15:42 ` Sam Halliday
2016-10-23 15:48 ` Eli Zaretskii
2016-10-23 15:58 ` Sam Halliday
2016-10-23 15:58 ` Sam Halliday
2016-10-23 16:44 ` Eli Zaretskii
2016-10-23 17:19 ` Eli Zaretskii
2016-10-23 18:06 ` Eli Zaretskii
2016-10-23 18:14 ` Noam Postavsky
2016-10-23 19:18 ` Eli Zaretskii
2016-10-24 13:29 ` npostavs
2016-10-24 13:39 ` Eli Zaretskii
2016-10-24 15:33 ` Noam Postavsky
2016-10-24 16:13 ` Eli Zaretskii
2016-10-25 2:00 ` npostavs
2016-10-25 16:03 ` Eli Zaretskii
2016-10-26 0:16 ` npostavs
2016-10-24 13:43 ` Eli Zaretskii
2016-10-24 14:03 ` Eli Zaretskii
2016-10-24 20:13 ` Sam Halliday
2016-10-24 23:44 ` npostavs
2016-11-07 3:39 ` Eli Zaretskii
2016-11-07 3:56 ` Noam Postavsky
2016-11-07 15:10 ` Eli Zaretskii
2016-10-23 18:16 ` Sam Halliday
2016-10-23 19:10 ` Eli Zaretskii
2016-10-23 19:32 ` Eli Zaretskii
2016-10-23 20:15 ` Sam Halliday
2016-10-23 20:27 ` Eli Zaretskii
2016-10-23 20:18 ` Eli Zaretskii
2016-10-23 23:18 ` Noam Postavsky
2016-10-24 7:05 ` Eli Zaretskii
2016-10-24 8:40 ` Eli Zaretskii
2016-10-23 18:11 ` Sam Halliday
2016-10-18 8:16 ` bug#24358: 25.1.50; Sam Halliday
2016-10-18 8:56 ` Sam Halliday
2016-10-18 9:28 ` Eli Zaretskii
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