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

[Alan Mackenzie <acm@muc.de>]

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.)  :-)

> 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!

> ~/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).