From: Bastian Beischer <bastian.beischer@gmail.com>
To: Alan Mackenzie <acm@muc.de>
Cc: 30367@debbugs.gnu.org
Subject: bug#30367: 26.0.91; CC-Mode: Major slowdown when isearching big C++ file.
Date: Wed, 7 Feb 2018 16:27:35 +0100 [thread overview]
Message-ID: <CAK9AuB-4YBHPMFBeniZ2vaq7uU+6xGqaQ+4gdjkGnWSjS2w0EQ@mail.gmail.com> (raw)
In-Reply-To: <20180207152435.72040.qmail@mail.muc.de>
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Hello Alan,
On Wed, Feb 7, 2018 at 4:24 PM, Alan Mackenzie <acm@muc.de> wrote:
> Hello, Bastian.
>
> In article <mailman.8662.1517913372.27995.bug-gnu-emacs@gnu.org> you
> wrote:
>
> > After updating CC-Mode to the latest version in the standalone mercurial
> > repository I noticed that searching large C++ files has become a lot
> > slower than before (factor 20 or so).
>
> Thanks for taking the trouble to report this bug.
>
> How large is large? Any chance you could supply me with such a sample
> C++ file that is slow on searching. Then, in case something else
> besides the size is slowing it down, I'll have a "working" file to
> diagnose the bug with.
>
Sure, but I will send you the file off-list, since I don't want it to
become public.
>
> > I traced the problem back to this commit:
>
> > Author: Alan Mackenzie <bug-cc-mode@gnu.org>
> > Date: Sun Jan 21 18:05:41 2018 +0000
>
> > Handle C99 Compound Literals in return statements and argument lists.
> >
> > * cc-engine.el (c-looking-at-or-maybe-in-bracelist): Recognize a
> brace list
> > when preceded by "return" or inside parentheses, either immediately
> after the
> > "(" or following a comma.
> > (c-looking-at-inexpr-block): Test c-has-compound-literals rather
> than hard
> > coded C++ Mode.
> > (c-guess-basic-syntax, CASE 7B): Test additionally for not being
> just inside a
> > parenthesis or being at a Java "new" keyword. CASE 9: Remove the
> simple
> > minded test on the contents of a block to determine a brace list.
> >
> > * cc-langs.el (c-has-compound-literals): New lang const and lang var.
> >
> > * bracelist-30.{c,res}: New test files.
>
> Thanks for getting this information. This should help track down the
> problem.
>
> > I am attaching the result of a run of the emacs profiler before
> > ("fast.profile") and after the commit ("slow.profile"). In this run I
> > started emacs as:
>
> > emacs -Q /path/to/big/file.C -e "(add-to-list 'load-path ~/cc-mode)" -e
> "(require 'cc-mode)"
> > M-x profiler-start
> > C-s searchString
> > M-x profiler-report
>
> > And write the result to 'slow.profile' and 'fast.profile'
> > respectively. It appears that 93% of the time is spent in
> > c-looking-at-or-maybe-in-bracelist.
>
> > Thanks for looking into this issue!
>
> Just as a matter of interest, you can post CC Mode bugs direct to
> bug-cc-mode@gnu.org. Sometimes a CC Mode dump produced by C-c C-b can
> be useful, though I don't think it would help much here.
>
Sorry, I didn't know that and will do it next time!
>
>
> > In GNU Emacs 26.0.91 (build 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.26)
> > of 2018-02-06 built on beischer-w520
> > Repository revision: c787a4968273027960a20ced6d63bae0d1ffa87e
> > Windowing system distributor 'The X.Org Foundation', version
> 11.0.11906000
>
> [ .... ]
>
> --
> Alan Mackenzie (Nuremberg, Germany).
>
Cheers
Bastian
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next prev parent reply other threads:[~2018-02-07 15:27 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-06 10:34 bug#30367: 26.0.91; CC-Mode: Major slowdown when isearching big C++ file Bastian Beischer
2018-02-06 10:40 ` Bastian Beischer
[not found] ` <mailman.8662.1517913372.27995.bug-gnu-emacs@gnu.org>
2018-02-07 15:24 ` Alan Mackenzie
[not found] ` <20180207152435.72040.qmail@mail.muc.de>
2018-02-07 15:27 ` Bastian Beischer [this message]
2018-02-07 21:21 ` Alan Mackenzie
[not found] ` <20180207212145.GA3963@ACM>
2018-02-07 21:53 ` Bastian Beischer
2018-02-07 22:26 ` Alan Mackenzie
2018-02-07 22:45 ` Bastian Beischer
2018-02-08 17:25 ` Alan Mackenzie
[not found] ` <20180208172558.GA4335@ACM>
2018-02-08 18:42 ` Alan Mackenzie
[not found] ` <20180208184232.GB4335@ACM>
2018-02-09 9:16 ` Bastian Beischer
2018-03-20 18:49 ` Alan Mackenzie
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