emacs hangs in c++ font-lock-modeo

emacs hangs in c++ font-lock-modeo

[Alan Mackenzie]

[cc to bug-cc-mode@gnu.org added.]

>From d.s.farin@tue.nl Fri Apr 15 20:33:22 2005

> Hi,

> I have got a C++ source file that causes "GNU Emacs 21.4.1" (current Debian
> testing) to hang with 100% cpu. To reproduce the bug, load the attached
> source file and turn font-lock-mode on in C++ mode. If you move the cursor
> down, at some position, emacs will hang and accept no more keyboard inputs.

Outch!  That's nasty.  I had that happen to me a couple of years ago.

I know that everything will still be set up to their defaults, but could
you perhaps give us some more details just the same:

How powerful is your computer?  (Processor speed in MHz or GHz).

What version of CC Mode have you got?  (M-x c-version)

Did you start your session with "emacs -q --no-site-file"?  (I.e. without
your .emacs and any site-lisp.el loaded.)  If not, do you still get the
problem when you do?

Does Emacs _always_ hang up, _usually_ hang up or _sometimes_ hang up?
How long does it take after loading the file before it hangs?  Does it
free up if you leave it running 8 or 12 hours or more?

How many other buffers have you got loaded at the same time, how big are
they (a few kilobytes, or a few hundred kilobytes), what modes are they
(other C++, perhaps)?

What support mode are you using in font lock?  (C-h v
font-lock-support-mode).  Probably jit-lock-mode, the default.  Does the
problem go away if you use lazy lock instead?  (Do M-: (setq
font-lock-support-mode 'lazy-lock-mode) before loading the buffer (or put
the setq in your .emacs, or do the same thing in the pertinent customize
buffer.))

Regards,
   Dirk

[OT good news:  My city council has just decided to use Debian as the
replacement for MS-Windows on its several thousand desktop PCs.  They're
hoping to start rolling it out at the end of this year.  :-]

-- 
Alan Mackenzie (Munich, Germany)

Re: emacs hangs in c++ font-lock-mode

[Dirk Farin]

First the good news: the problem does not appear anymore in the current
Emacs CVS version 22.0.50 (with cc-mode 5.30.9).

>>I have got a C++ source file that causes "GNU Emacs 21.4.1" (current Debian
>>testing) to hang with 100% cpu. To reproduce the bug, load the attached
>>source file and turn font-lock-mode on in C++ mode. If you move the cursor
>>down, at some position, emacs will hang and accept no more keyboard inputs.
> 
> I know that everything will still be set up to their defaults, but could
> you perhaps give us some more details just the same:
> 
> How powerful is your computer?  (Processor speed in MHz or GHz).

2.6 GHz, x86, but I tested on a variety of different systems with the
same result.

> What version of CC Mode have you got?  (M-x c-version)

"Using CC Mode version 5.28"

> Did you start your session with "emacs -q --no-site-file"?  (I.e. without
> your .emacs and any site-lisp.el loaded.)  If not, do you still get the
> problem when you do?

Does not change anything.

> Does Emacs _always_ hang up, _usually_ hang up or _sometimes_ hang up?

always

> How long does it take after loading the file before it hangs?  Does it
> free up if you leave it running 8 or 12 hours or more?

It occurs immediately. Start a new emacs, load the provided source code,
scroll down and it hangs.
I didn't check for several hours, but it stays locked for at least
10 minutes without increasing memory consumption.

> What support mode are you using in font lock?  (C-h v
> font-lock-support-mode).  Probably jit-lock-mode, the default.  Does the
> problem go away if you use lazy lock instead?  (Do M-: (setq

Yes, it it jit-lock-mode. If I switch to lazy mode, it locks already
while loading the file. Last message before it dies:
   "Fontifying emacs_hang.cc... (regexps...............)"





> [OT good news:  My city council has just decided to use Debian as the
> replacement for MS-Windows on its several thousand desktop PCs.  They're
> hoping to start rolling it out at the end of this year.  :-]

Ja, schoen. Habe ich auch gerade in den DLF Nachrichten gehoert.