which-function-mode keeps turning itself off

[Richard . G . Bielawski]

I kept having a problem with which-function-mode turning itself off.
I couldn't figure out what was causing it though.
On a whim I tried (setq debug-on-entry 'which-function-mode) and 
caught it turning itself off.  Apparently due to an error while
handling a timer.

I had just copied some text and was switching to the `temp' buffer.
See <menu-bar> <buffer> "temp" in the `Recent input:' section below.
The temp buffer was in fundamental-mode so didn't have which-function on.
Anyway, when debug-on-entry popped up I copied the backtrace info.
The <S-down> C-c <timeout> c c <C-tab> stuff is my using CUA to cut the 
debugger info and hitting c to continue from debug.  <C-tab> switched
me to the tal-mode buffer that used to have which-function turned on.
I confirmed that it was off and then you'll see  <menu-bar> <help-menu> 
<report-emacs-bug>.

Debugger entered--entering a function:
* which-func-mode(-1)
  byte-code("ÁÂ!^ÃÄ\"?" [info which-func-mode -1 error "Error in
which-func-update: %s"] 3)
  which-func-update-1(#<window 406 on temp>)
  which-func-update()
  apply(which-func-update nil)
  (condition-case nil (apply (aref timer 5) (aref timer 6)) (error nil))
  (let (retrigger) (cancel-timer timer) (if (aref timer 4) (if ... ... ...
... ... ...)) (condition-case nil (apply ... ...) (error nil)) (if retrigger
(aset timer 0 nil)))
  (if (timerp timer) (let (retrigger) (cancel-timer timer) (if ... ...)
(condition-case nil ... ...) (if retrigger ...)) (error "Bogus timer
event"))
  (let ((inhibit-quit t)) (if (timerp timer) (let ... ... ... ... ...)
(error "Bogus timer event")))
  timer-event-handler([t 0 0 500000 t which-func-update nil t])


In GNU Emacs 21.3.50 (i386-msvc-nt5.0.2195)
 of 2005-02-01 on LD1
Distributor `Microsoft Corp.', version 5.0.2195
configured using `configure --with-msvc (12.00)'

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: ENU
  locale-coding-system: iso-latin-1
  default-enable-multibyte-characters: t

Major mode: TAL

Minor modes in effect:
  eldoc-mode: t
  cua-mode: t
  recentf-mode: t
  show-paren-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  line-number-mode: t
  transient-mark-mode: t

Recent input:
<S-down> <S-down> <S-down> <S-down> <S-down> <S-down> 
<S-down> <S-down> <S-down> <S-down> <S-down> <S-down> 
<S-down> C-c <timeout> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <tool-bar> <kill-buffer> 
<help-echo> <menu-bar> <buffer> "temp" <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <up> <S-down> <S-down> <S-down> 
<S-down> <S-down> <S-down> <S-down> <S-down> <S-down> 
<S-down> <S-down> <S-down> C-c <timeout> c c <C-tab> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <help-echo> 
<help-echo> <help-echo> <help-echo> <help-echo> <menu-bar> 
<help-menu> <report-emacs-bug>

Recent messages:
cond: Search failed: "OCCUR"
Loading mule-diag...done
Quit
Next-Error-Follow minor mode disabled
Next-Error-Follow minor mode enabled
if: Search failed: "follow"
Entering debugger...
Continuing.
Entering debugger...
Continuing.
Richard Bielawski