GNU bug report logs - #61436
Emacs Freezing With Java Files

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Hank Greenburg <hank.greenburg <at> protonmail.com>
Subject: bug#61436: closed (Re: bug#61436: Emacs Freezing With Java Files)
Date: Sat, 14 Oct 2023 19:43:02 +0000

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Your bug report

#61436: Emacs Freezing With Java Files

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to 61436 <at> debbugs.gnu.org.

-- 
61436: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=61436
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Alan Mackenzie <acm <at> muc.de>
To: Jens Schmidt <jschmidt4gnu <at> vodafonemail.de>,
 Mats Lidell <mats.lidell <at> lidells.se>
Cc: Robert Weiner <rsw <at> gnu.org>, Hank Greenburg <hank.greenburg <at> protonmail.com>,
 61436-done <at> debbugs.gnu.org, acm <at> muc.de, Eli Zaretskii <eliz <at> gnu.org>,
 rswgnu <at> gmail.com
Subject: Re: bug#61436: Emacs Freezing With Java Files
Date: Sat, 14 Oct 2023 19:41:41 +0000

Hello, Jens and Mats.

On Fri, Oct 13, 2023 at 22:42:04 +0200, Jens Schmidt wrote:
> Hi Alan,

> Alan Mackenzie <acm <at> muc.de> writes:

> > To solve the bug, I'm amending the macro c-beginning-of-defun-1 so that
> > it only stops at a debug-prompt-regexp position when it also found a {.
> > Otherwise it will keep looping until it finds a better position or BOB.

> Thanks.

> > Then please confirm that the bug is indeed fixed.

> For the fun of it I tried Hank's initial testcase as well, which is a
> bit less straight-forward to set up.  The freezes are indeed gone with
> your patch.

Thanks for the testing.  Seeing as how both of you confirm the original
bug is fixed with the patch, I'm closing it with this post.

> But I noticed that which-function-mode, when rapidly moving through
> the file, cannot always determine the current function name, then
> displaying "[n/a]" in the mode line.

> And indeed, when executing the simplified test case

>   ./src/emacs -Q -l ~/tmp/init.el +181 ~/tmp/P1.java

> and then immediately hitting C-M-a, point jumps to the beginning of the
> preceeding catch clause (point=5779 of 18142) instead of BOD.

I can't reproduce this, even when setting defun-prompt-regexp to the
original large regexp from hui-select.el.

> This behavior is again tied to the `defun-prompt-regexp' used by
> Hyperbole - without that regexp C-M-a jumps to the real BOD.

Mats, I'm willing to work on that regular expression, and also the one
for C++.  As I mentioned earlier, I've got some tools which work on
regexps, in particular pp-regexp, which prints a regexp more readably on
several lines, and fix-re, which rewrites a regexp when it is
ill-conditioned in certain ways.

I foresee reverse engineering the regexps into more readable forms built
up by concatenating basic blocks.  For example for the java regexp I
would define

    (defconst id "[a-zA-Z][][_$.a-zA-Z0-9]*")

, and use this id in a largish concat form.

I'm also willing to share pp-regexp and fix-re with you(r team), if that
might help, on the understanding that neither is of release quality.

-- 
Alan Mackenzie (Nuremberg, Germany).

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From: Hank Greenburg <hank.greenburg <at> protonmail.com>
To: "bug-gnu-emacs <at> gnu.org" <bug-gnu-emacs <at> gnu.org>
Subject: Emacs Freezing With Java Files
Date: Sat, 11 Feb 2023 18:16:41 +0000

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I have a few Java files that are about 500 lines of code and I can't move around in them much before Emacs freezes. I first thought it was java-lsp but it still happened after disabling and uninstalling it. I also uninstalled lsp-mode as well, but that didn't change anything.

I started doing CPU profiles of it and found that which-function-mode was taking up 67% of my CPU usage. While this is happening all I was doing was holding the down arrow until it froze about 350 lines in. Didn't press any other buttons.

So I disabled which-function-mode and moved around the buffer just fine! Though when trying to edit the file (just hit enter), it froze again. This time it seems like electric-indent-mode was taking up close to 50% of my CPU usage.

I disabled that and tried again and then it froze again with c-indent-line-or-region eating up 63% of my CPU when I use TAB.

While using debug-on-quit I get the below output. Any idea what's happening here and how it can be addressed? I do know though that if I launch emacs with the -Q argument, then there aren't any problems at all. I tried large files of other types and it only seems to happen with Java files. I attached screenshots of the CPU profiler outputs for each of the three scenarios. Attached is also the Java file as well as my init file.

I am using emacs version 28.2 on EndeavorOS, but reproduced the results using both emacs 29 and the master branch.

Debugger entered--Lisp error: (quit)
beginning-of-defun()
c-get-fallback-scan-pos(17794)
c-parse-state-get-strategy(17794 1)
c-parse-state-1()
c-parse-state()
c-guess-basic-syntax()
c-indent-line()
#f(compiled-function () (interactive nil) #<bytecode 0x180248dcca1cc57e>)()
c-indent-command(nil)
c-indent-line-or-region(nil nil)
funcall-interactively(c-indent-line-or-region nil nil)
call-interactively(c-indent-line-or-region nil nil) command-execute(c-indent-line-or-region)

[Message part 5 (text/html, inline)]

[emacs-freezing-cpu-profile-indent-mode-off.png (image/png, attachment)]

[emacs-freezing-cpu-profile.png (image/png, attachment)]

[emacs-freezing-cpu-profile-no-function-mode.png (image/png, attachment)]

[P1.java (text/x-java, attachment)]

[init.org (text/org, attachment)]

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