bug#5490: 23.1.91; CC Mode, after a while, everything is topmost-intro.

[Alan Mackenzie <acm@muc.de>]

Hello, Jan,

On Fri, Jan 29, 2010 at 10:02:17AM +0100, Jan =?UTF-8?Q?Dj=C3=A4rv wrote:
> Hello.

First thing, sorry about the annoyance this bug is causing.

> This is one of those vague bug reports that aren't easy to reproduce.

Hmm.  It's also, unfortunately, one of these bug reports that are
difficult to respond to in a helpful manner.

> After using Emacs for some time (several hours, more than 4) and
> editing many C++ and C files, indentating breaks down.  This manifests
> itself that most lines get indetated at column 0.  Doing C-c c-s on
> those lines shows topmost-intro.  even if they should be inclass or
> statement.

"Most"?  Any chance you could post a fragment of a buffer (say, 20 - 60
lines starting near a beginning of defun) with the syntactic analysis of
each line (Use C-u C-c C-s on each line)?

OK.  Now some more details, please!

(i) Have you ever noticed this bug happening on earlier Emacsen, in
  particular Emacs 23.1?
(ii) Does this bug happen every time you use Emacs this long, or only
  sometimes?  If the latter, how often (10%, 50%, 90%)?
(iii) Do you think there might be any connection with some of the more
  unusual minor modes you've got switched on?  Things like
  auto-encryption mode?

When Emacs reaches this broken state:
(iv) Are all C(++) buffers in this state, or only some?  Any correlation
  with how many edits have been done on a buffer, or how long it's been
  loaded?
(v) What about indentation in a freshly loaded file?
(vi) Will M-x c-mode or M-x c++-mode clear the problem?
(vii) Does reverting (M-x revert-buffer) a file fix indentation?
(viii) Does killing and reloading a file fix indentation?
(ix) Does intentation gradually deteriorate at around 4 hours, or does it
  break suddenly?
(x) Do all CC Mode buffers break at the same time, or is it a "creeping
  death"?

I realise how tedious it is to reproduce the broken state, but answers to
these questions might suggest a line of attack on the bug.  Also, please
post any further thoughts you've had about it.

Just one other thing: Could you please post a dump of your CC Mode
configuration (C-c C-b in a C(++) buffer).  Thanks.

> Restarting Emacs fixes everything.

Well, that's one thing to be grateful for.  :-)

>            Jan D.

-- 
Alan Mackenzie (Nuremberg, Germany).