GNU bug report logs - #43631
28.0.50; CC Mode multiline strings grinds performance to a halt

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From: help-debbugs <at> gnu.org (GNU bug Tracking System)
To: Theodor Thornhill <theo <at> thornhill.no>
Subject: bug#43631: closed (Re: bug#43631: 28.0.50; CC Mode multiline
 strings grinds performance to a halt)
Date: Fri, 13 Oct 2023 15:28:02 +0000

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Your bug report

#43631: 28.0.50; CC Mode multiline strings grinds performance to a halt

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 43631 <at> debbugs.gnu.org.

-- 
43631: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=43631
GNU Bug Tracking System
Contact help-debbugs <at> gnu.org with problems

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From: Alan Mackenzie <acm <at> muc.de>
To: 43631-done <at> debbugs.gnu.org
Subject: Re: bug#43631: 28.0.50; CC Mode multiline strings grinds performance
 to a halt
Date: Fri, 13 Oct 2023 15:26:36 +0000

Hello, Emacs.

This bug was fixed with my commits between 2021-08-12 and 2021-08-14.

Closing.

-- 
Alan Mackenzie (Nuremberg, Germany).

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From: Theodor Thornhill <theo <at> thornhill.no>
To: bug-gnu-emacs <at> gnu.org
Subject: 28.0.50; CC Mode multiline strings grinds performance to a halt
Date: Sat, 26 Sep 2020 13:17:29 +0200

Hello there!

While creating a new mode derived from CC Mode, we noticed performance
is affected heavily when setting a character for
'c-multiline-string-start-char'. There is a discussion around this that
can be found at https://github.com/josteink/csharp-mode/issues/164,
and we were given an easily reproducible repo for this. It is verified
to slow typing down both in 'csharp-mode', 'pike-mode' and in this test
case:
https://github.com/unhammer/csharp-mode/tree/164-repro

I think (unconvincingly) that some of the problematic code is situated
around line 2047 in 'cc-mode.el', but this is only a guess taken from
some light profiling.

The issue is described well on github, and I think me trying to
reiterate that here will only cause subtle confusions.

One thing of note is that you don't even have to have any multiline
strings for this performance hit to occur, meaning all 'csharp-mode'
files do suffer from this.

Let me know if something is still unclear, and I'll try to bring up some
more information.

All the best,
Theodor Thornhill

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