Re: I seek QA for CPerl 5.2 (Emacs mode)

["Randy W. Sims" <RandyS@ThePierianSpring.org>]

Ilya Zakharevich wrote:
> [A complimentary Cc of this posting was sent to
> Randy W. Sims
> <RandyS@thepierianspring.org>], who wrote in article <435556D7.7030303@thepierianspring.org>:
> 
>> One wierd problem I find is if I load two copies of a certain file it 
>> becomes develishly slow to do anything, even scrolling. This doesn't 
>> seem to happen on all files; not sure if it's size or content related yet.
>>
>> Eg, If I unpack the Module::Build distribution into two different 
>> directories, then load copies of Module/Build/Base.pm from each 
>> location, the second buffer becomes slow. The original buffer and any 
>> others are not affected. If I close both buffers, then open the same 
>> file again, the new buffer is also slow-I must exit emacs and restart 
>> before I can work with that particular file because of slowdown.
> 
>> This is on Debian (testing) with GNU Emacs 21.4.1.
> 
> Confirmed on 21.2.  This effect disappears if I switch to an older
> version of font-lock (e.g., one on
>   ilyaz.org/software/tmp/font-lock-old.zip
> ).  One does not need to load the same file or a large file; two files
> of size about 80K show the same slowdown in
> fontification-by-keywords.  (I used Build.pm and Build/Base.pm.)
> 
> Go to the ends of both buffers, then start to scroll back - it is
> painfully slow in one of the buffers...
> 
> I have no idea how to debug this...  My conjecture is that newer
> Font-lock somehow starts to think that it needs to fontify the full
> buffer instead of doing only the visible part...

Unfortunately, I don't know much lisp, so I can't help there. I did just 
try it out on my Windows box with XEmacs 21.4.17, same emacs init file. 
I see no sign of the above problem. The font-lock.el here is:

;; Copyright (C) 1992-1995, 1997 Free Software Foundation, Inc.
;; Copyright (C) 1995 Amdahl Corporation.
;; Copyright (C) 1996, 2000, 2001 Ben Wing.

;; Author: Jamie Zawinski <jwz@jwz.org>, for the LISPM Preservation Society.
;; Minimally merged with FSF 19.34 by Barry Warsaw <bwarsaw@python.org>
;; Then (partially) synched with FSF 19.30, leading to:
;; Next Author: RMS
;; Next Author: Simon Marshall <simon@gnu.ai.mit.edu>
;; Latest XEmacs Author: Ben Wing
;; Maintainer: XEmacs Development Team
;; Keywords: languages, faces