Re: Mysterious fontification/C++ context issue

[Jan Djärv]

Tim Van Holder skrev:
> 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.

I see this too a lot, even in plain C files.  A backtrace when this happen 
looks like this:

Debugger entered--Lisp error: (scan-error "Containing expression ends 
prematurely" 107612 107612)
  scan-lists(107699 -1 0)
  forward-list(-1)
  backward-list(1)
  beginning-of-defun-raw(nil)
  beginning-of-defun()
  c-get-fallback-start-pos(108117)
  c-parse-state()
  c-electric-semi&comma(nil)
  call-interactively(c-electric-semi&comma)
  call-last-kbd-macro(nil kmacro-loop-setup-function)
  kmacro-call-macro(nil nil)
  kmacro-end-and-call-macro(nil)
  call-interactively(kmacro-end-and-call-macro)

Usually moving the cursor up a few lines, hitting tab to indent that line, and 
then move back to the offending line cures it.

        Jan D.