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bug#18134: 24.3; Doxygen comments trigger anomalous C++ major mode behav
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From: |
Alan Mackenzie |
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Subject: |
bug#18134: 24.3; Doxygen comments trigger anomalous C++ major mode behavior |
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Date: |
Sat, 19 Oct 2019 16:13:05 +0000 |
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User-agent: |
Mutt/1.10.1 (2018-07-13) |
Hello, Stefan and Sam.
On Mon, Oct 07, 2019 at 00:42:46 +0200, Stefan Kangas wrote:
> found 27.0.50
> thanks
> Sam Varshavchik <sam.varshavchik@gmail.com> writes:
> > I am seeing anomalous behavior in C++ major mode that's triggered by
> > long, but not excessively long -- only a few hundred lines -- Doxygen-style
> > comments.
> > Cursor navigation at the end of the Doxygen comment block in the
> > following file (just before the first typedef), and trying to add some
> > additional text there, results in 3-5 seconds' worth of delays for
> > nearly typed character.
> > Highlighting the entire Doxygen comment block: M-x indent-region takes
> > several minutes (!) with emacs consuming 100% CPU.
> [Snipped a long C++ example file here.]
> I can reproduce both issues on current master using the provided example
> file.
> 1. Editing is very slow after the Doxygen comment block.
> 2. Opening the example file under "emacs -Q", pressing C-x h TAB takes
> several minutes and sees the emacs process consume 100 % CPU (on one
> core at least).
Yes. Some optimisation is needed in c-crosses-statement-barrier-p for
large blocks of comments. Please try out this patch, and let me know if
anything untoward happens:
diff -r d84523ed901e cc-engine.el
--- a/cc-engine.el Sat Oct 12 08:55:31 2019 +0000
+++ b/cc-engine.el Sat Oct 19 16:06:23 2019 +0000
@@ -1474,10 +1474,13 @@
(progn
(if (setq lit-start (c-literal-start from)) ; Have we
landed in a string/comment?
(goto-char lit-start))
- (c-backward-syntactic-ws) ; ? put a limit here, maybe?
+ (c-backward-syntactic-ws (c-point 'bopl))
(setq vsemi-pos (point))
(c-at-vsemi-p))))
(throw 'done vsemi-pos))
+ ((progn (c-forward-syntactic-ws to)
+ (>= (point) to))
+ (throw 'done nil))
;; In a string/comment?
((setq lit-range (c-literal-limits from))
(goto-char (cdr lit-range)))
> Using the profiler during step 2 gives me:
> >- command-execute 59856 97%
> > - call-interactively 59856 97%
> > - funcall-interactively 59827 97%
> > - c-indent-line-or-region 59820 97%
> > - c-indent-region 59819 97%
> > - c-guess-basic-syntax 59809 97%
> > - c-beginning-of-statement-1 39327 63%
> > - c-crosses-statement-barrier-p 39105 63%
> > <====
> > - c-backward-sws 22222 36%
> > + c-beginning-of-macro 492 0%
> > #<compiled 0x1579d1980ead> 1 0%
> > c-literal-limits 9508 15%
> > c-literal-start 6228 10%
> > + c-at-macro-vsemi-p 217 0%
> > + c-backward-sws 61 0%
> > + c-at-macro-vsemi-p 16 0%
> > + c-beginning-of-macro 10 0%
> > - c-just-after-func-arglist-p 19872 32%
> > - c-beginning-of-statement-1 19872 32%
> > - c-crosses-statement-barrier-p 19795 32%
> > - c-backward-sws 11424 18%
> > + c-beginning-of-macro 287 0%
> > #<compiled 0x1579d1980ead> 2 0%
> > c-literal-limits 4707 7%
> > c-literal-start 3095 5%
> > + c-at-macro-vsemi-p 121 0%
> > + c-backward-sws 17 0%
> > c-beginning-of-macro 2 0%
> > c-at-macro-vsemi-p 1 0%
> > + c-looking-at-inexpr-block 1 0%
> > + c-backward-sws 202 0%
> > + c-back-over-member-initializers 106 0%
> > + c-determine-limit 103 0%
> > + c-parse-state 61 0%
> > + c-looking-at-decl-block 55 0%
> > + c-looking-at-inexpr-block 19 0%
> > + c-syntactic-skip-backward 13 0%
> > + c-back-over-member-initializer-braces 4 0%
> > + c-beginning-of-decl-1 4 0%
> > + c-in-literal 3 0%
> > + c-at-macro-vsemi-p 1 0%
> > + c-inside-bracelist-p 1 0%
> > + c-at-statement-start-p 1 0%
> > + c-indent-line 9 0%
> > + execute-extended-command 7 0%
> > - byte-code 29 0%
> > + read-extended-command 29 0%
> >+ ... 1784 2%
> (Quoted above so Gmail doesn't mess it up...)
> Best regards,
> Stefan Kangas
--
Alan Mackenzie (Nuremberg, Germany).