GNU bug report logs - #55744
infinite loop

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Message #5 received at submit <at> debbugs.gnu.org (full text, mbox):

From: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
To: bug-gnu-emacs <at> gnu.org
Subject: infinite loop
Date: Tue, 31 May 2022 12:49:35 -0700

[Message part 1 (text/plain, inline)]

The attached file contains the string "end--" in two places.  When
searching for that string with M-x isearch-forward (C-s) in that file,
just after opening the file, starting from the top of the file, it often
happens, that after positioning the cursor at the first "end" in the file,
it displays "end-" on the mode line and then goes into an infinite loop,
not responding to further input or making any further
progress on the search.




In GNU Emacs 28.1 (build 1, x86_64-apple-darwin18.7.0, NS appkit-1671.60
Version 10.14.6 (Build 18G95))
 of 2022-04-22 built on builder10-14.lan
Windowing system distributor 'Apple', version 10.3.2113
System Description:  macOS 12.3

Configured using:
 'configure --with-ns '--enable-locallisppath=/Library/Application
 Support/Emacs/${version}/site-lisp:/Library/Application
 Support/Emacs/site-lisp' --with-modules'

Configured features:
ACL GMP GNUTLS JSON LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER THREADS
TOOLKIT_SCROLL_BARS ZLIB

Important settings:
  value of $EMACSLOADPATH:
/Applications/LilyPond.app/Contents/Resources/share/emacs/site-lisp:/Users/dan/local/share/emacs/site-lisp:/usr/local/share/emacs/site-lisp:
  value of $LC_ALL: en_US.UTF-8
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Info

Minor modes in effect:
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Load-path shadows:
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/Users/dan/emacs/gedcom hides /Users/dan/home/emacs/gedcom
/Users/dan/src/M2/M2.git/M2/Macaulay2/editors/emacs/M2-symbols hides
/usr/local/share/emacs/site-lisp/macaulay2/M2-symbols
/Users/dan/src/M2/M2.git/M2/Macaulay2/editors/emacs/M2 hides
/usr/local/share/emacs/site-lisp/macaulay2/M2
/Users/dan/src/M2/M2.git/M2/Macaulay2/editors/emacs/M2-init hides
/usr/local/share/emacs/site-lisp/macaulay2/M2-init
/Users/dan/src/M2/M2.git/M2/Macaulay2/editors/emacs/M2-mode hides
/usr/local/share/emacs/site-lisp/macaulay2/M2-mode
/Users/dan/emacs/rmail hides
/Applications/Emacs.app/Contents/Resources/lisp/mail/rmail
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/Applications/Emacs.app/Contents/Resources/lisp/obsolete/longlines

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Memory information:
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 (string-bytes 1 1513842)
 (vectors 16 26190)
 (vector-slots 8 305278 27939)
 (floats 8 93 32)
 (intervals 56 7639 129)
 (buffers 992 27))

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Message #8 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Tue, 31 May 2022 22:12:40 +0200

"Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:

> The attached file contains the string "end--" in two places.  When
> searching for that string with M-x isearch-forward (C-s) in that file,
> just after opening the file, starting from the top of the file, it
> often happens, that after positioning the cursor at the first "end" in
> the file, it displays "end-" on the mode line and then goes into an
> infinite loop, not responding to further input or making any further
> progress on the search.

I'm unable to reproduce this in Emacs 28.1 (on Debian/bookworm).  Is
this with "emacs -Q"?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #11 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Tue, 31 May 2022 13:26:19 -0700

[Message part 1 (text/plain, inline)]

Nope, no command line options.

On Tue, May 31, 2022 at 1:12 PM Lars Ingebrigtsen <larsi <at> gnus.org> wrote:

> "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:
>
> > The attached file contains the string "end--" in two places.  When
> > searching for that string with M-x isearch-forward (C-s) in that file,
> > just after opening the file, starting from the top of the file, it
> > often happens, that after positioning the cursor at the first "end" in
> > the file, it displays "end-" on the mode line and then goes into an
> > infinite loop, not responding to further input or making any further
> > progress on the search.
>
> I'm unable to reproduce this in Emacs 28.1 (on Debian/bookworm).  Is
> this with "emacs -Q"?
>
> --
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no
>

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Message #14 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Tue, 31 May 2022 22:28:32 +0200

"Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:

> Nope, no command line options.

I mean, can you reproduce this problem with "emacs -Q" (which makes
Emacs start up without reading your init files)?

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #17 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Tue, 31 May 2022 13:42:27 -0700

[Message part 1 (text/plain, inline)]

Ah, indeed, the bug doesn't seem to be reproducible with "-Q".  I attach my
.emacs and .emacs-Macaulay2.

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[.emacs (application/octet-stream, attachment)]

[.emacs-Macaulay2 (application/octet-stream, attachment)]

Message #20 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Wed, 01 Jun 2022 04:29:39 +0200

"Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:

> Ah, indeed, the bug doesn't seem to be reproducible with "-Q".  I
> attach my .emacs and .emacs-Macaulay2.

Try removing things from those to determine what triggers the problem.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #25 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Wed, 1 Jun 2022 07:27:22 -0700

[Message part 1 (text/plain, inline)]

Okay, I did that, and it seems to be this:

(defconst M2-mode-font-lock-keywords ' (
"///\\(/?/?[^/]\\|\\(//\\)*////[^/]\\)*\\(//\\)*///" .
'font-lock-string-face) )
(define-derived-mode M2-mode prog-mode "Macaulay2" (setq font-lock-defaults
'( M2-mode-font-lock-keywords )) )
(add-to-list 'auto-mode-alist '("\\.m2\\'" . M2-mode))

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Message #28 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Wed, 01 Jun 2022 17:35:04 +0200

"Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:

> Okay, I did that, and it seems to be this:
>
> (defconst M2-mode-font-lock-keywords
>           '("///\\(/?/?[^/]\\|\\(//\\)*////[^/]\\)*\\(//\\)*///" .
> 'font-lock-string-face) )

That's a regexp with a lot of backtracking, I think (i.e., elements that
can be matched both by the ?'s as well as the two *'s).  So matching
this will be slow, which results in the hangs you're seeing when Emacs
is trying to match that to the text in the buffer.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #31 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Wed, 1 Jun 2022 08:47:38 -0700

[Message part 1 (text/plain, inline)]

Ah, you're right -- if I wait 45 seconds or so, it finally finishes and
moves on,
and that file has strings that should have matched it.  And it needs to
match all the text
from the start of the file, since string starts and string ends look the
same.  And the result is the same
if I search for any other string that first occurs deep into the file.

Thanks, it's not a bug in emacs!



On Wed, Jun 1, 2022 at 8:35 AM Lars Ingebrigtsen <larsi <at> gnus.org> wrote:

> "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:
>
> > Okay, I did that, and it seems to be this:
> >
> > (defconst M2-mode-font-lock-keywords
> >           '("///\\(/?/?[^/]\\|\\(//\\)*////[^/]\\)*\\(//\\)*///" .
> > 'font-lock-string-face) )
>
> That's a regexp with a lot of backtracking, I think (i.e., elements that
> can be matched both by the ?'s as well as the two *'s).  So matching
> this will be slow, which results in the hangs you're seeing when Emacs
> is trying to match that to the text in the buffer.
>
> --
> (domestic pets only, the antidote for overdose, milk.)
>    bloggy blog: http://lars.ingebrigtsen.no
>

[Message part 2 (text/html, inline)]

Message #34 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Lars Ingebrigtsen <larsi <at> gnus.org>
To: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
Cc: 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Wed, 01 Jun 2022 17:48:45 +0200

"Daniel R. Grayson" <danielrichardgrayson <at> gmail.com> writes:

> Thanks, it's not a bug in emacs!

Thanks; I'm closing this bug report, then.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no

Message #41 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Richard Stallman <rms <at> gnu.org>
To: Lars Ingebrigtsen <larsi <at> gnus.org>
Cc: danielrichardgrayson <at> gmail.com, 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Mon, 06 Jun 2022 18:15:06 -0400

[[[ To any NSA and FBI agents reading my email: please consider    ]]]
[[[ whether defending the US Constitution against all enemies,     ]]]
[[[ foreign or domestic, requires you to follow Snowden's example. ]]]

  > That's a regexp with a lot of backtracking, I think (i.e., elements that
  > can be matched both by the ?'s as well as the two *'s).  So matching
  > this will be slow, which results in the hangs you're seeing when Emacs
  > is trying to match that to the text in the buffer.

Would it make sense to say more about this point in the Emacs Lisp Manual
where it describes regexps?

-- 
Dr Richard Stallman (https://stallman.org)
Chief GNUisance of the GNU Project (https://gnu.org)
Founder, Free Software Foundation (https://fsf.org)
Internet Hall-of-Famer (https://internethalloffame.org)

Message #44 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: "Daniel R. Grayson" <danielrichardgrayson <at> gmail.com>
To: rms <at> gnu.org
Cc: Lars Ingebrigtsen <larsi <at> gnus.org>, 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Mon, 6 Jun 2022 15:46:02 -0700

[Message part 1 (text/plain, inline)]

Conceivably, although I wasn't referring to the manual, even after I
isolated the offending
regexp.

On Mon, Jun 6, 2022 at 3:15 PM Richard Stallman <rms <at> gnu.org> wrote:

> [[[ To any NSA and FBI agents reading my email: please consider    ]]]
> [[[ whether defending the US Constitution against all enemies,     ]]]
> [[[ foreign or domestic, requires you to follow Snowden's example. ]]]
>
>   > That's a regexp with a lot of backtracking, I think (i.e., elements
> that
>   > can be matched both by the ?'s as well as the two *'s).  So matching
>   > this will be slow, which results in the hangs you're seeing when Emacs
>   > is trying to match that to the text in the buffer.
>
> Would it make sense to say more about this point in the Emacs Lisp Manual
> where it describes regexps?
>
> --
> Dr Richard Stallman (https://stallman.org)
> Chief GNUisance of the GNU Project (https://gnu.org)
> Founder, Free Software Foundation (https://fsf.org)
> Internet Hall-of-Famer (https://internethalloffame.org)
>
>
>

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Message #47 received at 55744 <at> debbugs.gnu.org (full text, mbox):

From: Eli Zaretskii <eliz <at> gnu.org>
To: rms <at> gnu.org
Cc: larsi <at> gnus.org, danielrichardgrayson <at> gmail.com, 55744 <at> debbugs.gnu.org
Subject: Re: bug#55744: infinite loop
Date: Tue, 07 Jun 2022 05:28:08 +0300

> Cc: danielrichardgrayson <at> gmail.com, 55744 <at> debbugs.gnu.org
> From: Richard Stallman <rms <at> gnu.org>
> Date: Mon, 06 Jun 2022 18:15:06 -0400
> 
>   > That's a regexp with a lot of backtracking, I think (i.e., elements that
>   > can be matched both by the ?'s as well as the two *'s).  So matching
>   > this will be slow, which results in the hangs you're seeing when Emacs
>   > is trying to match that to the text in the buffer.
> 
> Would it make sense to say more about this point in the Emacs Lisp Manual
> where it describes regexps?

I think we already do, see the node "Regexp Problems" there.

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