Mysterious fontification/C++ context issue

[Tim Van Holder]

For a few weeks now, I've had intermittent issues editing C++ code in
Emacs; I was hoping to find some minimal reproducible case, but have
been unable to do so.

The symptoms are that while editing a C++ source file (typically
happens when killing or yanking, but I think I've seen it happen
with regular editing), fontification of the currently visible buffer
contents will fail. Scrolling shows other parts of the buffer are still
fontified correctly.  All in all this is a minor inconvenience, but
more annoyingly, it also affects C++-mode when it comes to indentation:
TAB and the electric characters (comma, parens) throw a

  (scan-error Containing expression ends prematurely nnnn mmmm)

(with the range indicating the current function).  Sometimes scrolling
back and forth far enough resolves this, sometimes more drastic
measures are needed (font-lock-fontify-buffer tends to clear it up,
as does normal-mode).
I'm not sure where the problem lies -- could be a cc-mode issue, could
be a font-lock issue, could be something else -- so I'm afraid I
cannot be of much help.


In GNU Emacs 22.0.91.1 (i686-pc-linux-gnu, GTK+ Version 2.8.20)
 of 2006-12-04 on leeloo
X server distributor `RealVNC Ltd', version 11.0.3370
configured using `configure '--with-gtk' '--with-xpm' '--with-jpeg'
 '--with-gif' '--with-tiff' '--with-png' '--with-x' '--with-kerberos'
 '--with-kerberos5''

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_US.UTF-8
  locale-coding-system: utf-8
  default-enable-multibyte-characters: t

Major mode: C++/l

Minor modes in effect:
  whitespace-global-mode: t
  show-paren-mode: t
  pc-selection-mode: t
  display-time-mode: t
  delete-selection-mode: t
  tooltip-mode: t
  tool-bar-mode: t
  mouse-wheel-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  unify-8859-on-encoding-mode: t
  utf-translate-cjk-mode: t
  auto-compression-mode: t
  column-number-mode: t
  line-number-mode: t
  transient-mark-mode: t
  abbrev-mode: t