bug#30367: 26.0.91; CC-Mode: Major slowdown when isearching big C++ file.

[Bastian Beischer <bastian.beischer@gmail.com>]

On Wed, Feb 7, 2018 at 11:26 PM, Alan Mackenzie <acm@muc.de> wrote:
> Hello, Bastian.
>
> On Wed, Feb 07, 2018 at 22:53:47 +0100, Bastian Beischer wrote:
>> Hello Alan,
>
>> On Wed, Feb 7, 2018 at 10:21 PM, Alan Mackenzie <acm@muc.de> wrote:
>
> [ .... ]
>
>> > Unfortunately, I cannot reproduce the slowdown in that file, at least,
>> > not starting from emacs-26.0.91 -Q.  I think you've got quite a lot of
>> > non-default minor modes active, and I've a suspicion that we're seeing
>> > some interaction between CC Mode and one of these minor modes, or
>> > possibly some other non-default setting you've got set.
>
>> > Would you please try to reproduce the problem with emacs -Q, and if you
>> > can't, try to pinpoint which one of your settings/minor modes is the one
>> > which CC Mode is working badly with.
>
>> Actually the profile runs I sent were done with 'emacs -Q'. It's just
>> that I used a different emacs instance to report the bug, which had
>> the usual modes loaded. Sorry about that. So I can reproduce the
>> problem from emacs -Q, but I _do_ load the latest cc-mode from it's
>> standalone repository. The actual command was:
>
>> emacs -Q --eval "(add-to-list 'load-path \"~/cc-mode\")" --eval
>> "(require 'cc-mode)" /path/to/file.C
>
> As a matter of interest, you can run
>
>     emacs -Q -L ~/cc-mode /path/to/file.C
>
> , this being less effort to type.  (I don't understand why you've got the
> `require' form in there - maybe you really do need it.)  :-)

Yes the command you sent works just as well, so the require form is
not needed. Thanks!

>
>> then search for 'isinsha'.
>
> Yes, searching for "isinsha", I see the slowdown.  Thanks!  I also see
> c-looking-at-or-maybe-in-bracelist as taking an excessive amount of
> processing.
>
> So I can reproduce it!

Great, so our results are consistent.

>
>> ~/cc-mode revision is as follows:
>
>> $ cd ~/cc-mode
>> $ hg summary
>> parent: 6256:e8b2c6141f97
>> Added tag 2018-01-29-mac-m for changeset 9785123a85b4
>> branch: default
>> commit: (clean)
>> update: (current)
>
> Thanks.  I actually run the tip of the standalone CC Mode as my default
> CC Mode anyway, since I'm so often working on it.
>
>> emacs version is as in the original report (GNU Emacs 26.0.91 (build
>> 1, x86_64-pc-linux-gnu, GTK+ Version 3.22.26) of 2018-02-06, commit
>> c787a4968273027960a20ced6d63bae0d1ffa87e)
>
>
>
>> > We'll crack this!
>
>> I'm sure :-)
>
> Just not tonight.  ;-)
>
>> Cheers
>> Bastian
>
> --
> Alan Mackenzie (Nuremberg, Germany).