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From: Eli Zaretskii <eliz@gnu.org>
To: Yuan Fu <casouri@gmail.com>
Cc: 59426@debbugs.gnu.org
Subject: bug#59426: 29.0.50; [tree-sitter] Some functions exceed maximum recursion limit
Date: Mon, 21 Nov 2022 19:16:06 +0200	[thread overview]
Message-ID: <83bkp02ppl.fsf@gnu.org> (raw)
In-Reply-To: <CDDFCA51-1294-4743-93B2-92E31490F4A9@gmail.com> (message from Yuan Fu on Mon, 21 Nov 2022 08:52:53 -0800)

> From: Yuan Fu <casouri@gmail.com>
> Date: Mon, 21 Nov 2022 08:52:53 -0800
> Cc: 59426@debbugs.gnu.org
> 
> 
> 
> > On Nov 21, 2022, at 5:19 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> > 
> >> From: Yuan Fu <casouri@gmail.com>
> >> Date: Sun, 20 Nov 2022 16:53:45 -0800
> >> 
> >> 
> >> Emacs crashed on a very large C file when c-ts-mode is on, because
> >> the function building the imenu list tries to walk through the whole
> >> parse tree, and end up recusing ~10k times because of how deep the parse
> >> tree is. These recursive functions should have a built-in limit. Does
> >> Emacs already have some way to determined the max recursion limit on
> >> each system? Or should we come up with some hard-coded numbers?
> > 
> > Is the recursion in our code, or is it in libtree-sitter?
> 
> In our code, when we walk the parse tree.
> 
> > 
> > If the former, one solution, albeit a crude one, is to track the recursion
> > level and error out if it becomes too deep.  Another solution is to handle
> > the stack in our code, in which case the stack can be allocated on the heap.
> 
> That’s my idea, hence my asking for a reasonable way to get a limit. I think a hard limit is totally reasonable, because there is no way for a “normal” parse tree to be 10k levels deep (that means the source program is 10k levels deep, ver unlikely for any program a human would write or a machine would generated). The one I observed is likely due to the parser misunderstanding the source (due to errors in the code). Plus, I don’t think any user would want to walk that deep into the parse tree either. If someone expects to walk that deep into a parse tree, her program is ill-designed.

How many bytes does each recursive invocation need on the stack?  With that
number at hand, we can estimate a safe value for the limit.  And don't
forget that GC is also highly recursive and eats up a lot of stack space.
I guess GC can happen during building of the imenu list?





      reply	other threads:[~2022-11-21 17:16 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-11-21  0:53 bug#59426: 29.0.50; [tree-sitter] Some functions exceed maximum recursion limit Yuan Fu
2022-11-21  6:40 ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-21  7:38   ` Stefan Kangas
2022-11-21 12:00     ` Mattias Engdegård
2022-11-21 13:55       ` Eli Zaretskii
2022-11-21 14:46         ` Mattias Engdegård
2022-11-21 16:43           ` Yuan Fu
2022-11-21 16:54             ` Eli Zaretskii
2022-11-21 17:10               ` Eli Zaretskii
2022-11-21 17:45                 ` Eli Zaretskii
2022-11-21 18:20                   ` Mattias Engdegård
2022-11-21 18:26                     ` Eli Zaretskii
2022-11-21 18:59                       ` Mattias Engdegård
2022-11-21 19:00                     ` Yuan Fu
2022-11-22  9:08                       ` Mattias Engdegård
2022-11-22 23:19                         ` Yuan Fu
2022-11-23 10:40                           ` Mattias Engdegård
2022-11-23 18:46                             ` Yuan Fu
2022-11-23 20:01                               ` Mattias Engdegård
2022-11-24  9:17                                 ` Yuan Fu
2022-11-24 10:24                                   ` Mattias Engdegård
2022-11-24 19:25                                     ` Yuan Fu
2022-11-24 19:28                                       ` Eli Zaretskii
2022-11-27  2:36                                         ` Yuan Fu
2022-11-24 10:24                                   ` Eli Zaretskii
2022-11-21 16:56             ` Mattias Engdegård
2022-11-21 17:01               ` Yuan Fu
2022-11-21 17:44               ` Eli Zaretskii
2022-11-22  1:46             ` Stefan Kangas
2022-11-22  0:27       ` Po Lu via Bug reports for GNU Emacs, the Swiss army knife of text editors
2022-11-22  8:59         ` Mattias Engdegård
2022-11-21 13:19 ` Eli Zaretskii
2022-11-21 16:52   ` Yuan Fu
2022-11-21 17:16     ` Eli Zaretskii [this message]

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