bug#10149: Emacs 24 hangs for several minutes with very large c++ files

[suvayu ali]

Hi Emacs devs,

I am seeing a weird problem. I have an automatically generated C++ class
for some ntupled data for quick (but dirty) analysis. It has lots of
(~1k) data members. Every time I try to navigate in that file and I
reach the large block of text where the data members are declared[1],
Emacs takes a long time to move the cursor (e.g. with commands like
forward-paragraph or backward-paragraph) and the CPU usage on my
Thinkpad X201 maxes out on one of the 4 logical cores. If I wait long
enough (several minutes), Emacs 24 does manage to move the cursor to the
end of the paragraph. However I don't see this problem with Emacs 23.3.1
(or vim).

I can replicate this behaviour with `emacs -Q'. The file that causes the
issue is attached with this email. I am using Emacs from the repo.or.cz
git mirror.

commit aecaa1ffa122258c0fbc580ccbfad268ea46b89d
Author: Andreas Schwab <schwab@linux-m68k.org>
Date:   Sat Nov 26 10:10:36 2011 +0100

    * grammars/bovine-grammar.el (bovine--grammar-newstyle-unquote):
    Avoid warning about old-style backquote.

This is how I compile emacs:

In GNU Emacs 24.0.91.1 (x86_64-unknown-linux-gnu, GTK+ Version 2.24.7)
 of 2011-11-27 on mylaptop.example.com
configured using `configure  '--prefix=/opt/emacs-lisp'
'--with-selinux' '--with-imagemagick''

Important settings:
  value of $LC_ALL: nil
  value of $LC_COLLATE: nil
  value of $LC_CTYPE: nil
  value of $LC_MESSAGES: nil
  value of $LC_MONETARY: nil
  value of $LC_NUMERIC: nil
  value of $LC_TIME: nil
  value of $LANG: en_IN.UTF-8
  value of $XMODIFIERS: @im=ibus
  locale-coding-system: utf-8-unix
  default enable-multibyte-characters: t

Since I don't actually get a backtrace, I am not sure what else I can
provide. Please feel free to ask me if you need more information.

Hope this helps.

Footnotes:

[1] The large chunk of commented text in the attached file

-- 
Suvayu

Open source is the future. It sets us free.

bug.hxx
Description: Text document