Re: Mysterious fontification/C++ context issue

[martin rudalics <rudalics@gmx.at>]

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 > Here's a tentative fix for the bug, not that well tested, but tested a
 > little bit:
 >
 > 2006-12-04  Alan Mackenzie  <acm@muc.de>
 >
 >     * emacs-lisp/lisp.el (beginning-of-defun-raw): In the seeking a
 >     non-nested open-paren case, check there are enough lists to move
 >     over.  Return the correct value.

Thanks for taking care of this.  Please note:

1. You don't widen the buffer before calling `syntax-ppss'.

2. A construct built along

(foo
) (bar)

with point at "bar" might derail font-lock (remember,
`c-beginning-of-defun-1' calls `beginning-of-defun', not
`beginning-of-defun-raw').

3. All this is still awfully slow and expensive: Open a larger buffer
like xdisp.c, jump to its end, hit M-v a couple of times, and look at
CPU consumption.

4. You could avoid the tedious `up-list' steps by using a variant of the
tentative fix I attached.

5. Consider making `open-paren-in-column-0-is-defun-start' a real user
option in C mode.  Let, for example, users decide whether they want to
respect GNU coding standards as mentioned in

http://lists.gnu.org/archive/html/bug-gnu-emacs/2006-11/msg00037.html

This should also permit binding C-M-a / C-M-e to `c-beginning-of-defun'
/ `c-end-of-defun' when `open-paren-in-column-0-is-defun-start' is nil.

6. In any case, the new behavior should be documented since it applies
whenever `open-paren-in-column-0-is-defun-start' is set to nil.

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*** lisp.el	Thu Nov  9 07:55:26 2006
--- lisp.el	Wed Dec  6 08:53:18 2006
***************
*** 229,271 ****
  			       "^\\s(")
  			     nil 'move arg)
  	 (progn (goto-char (1- (match-end 0)))) t))
- 
     (t
!     ;; Column 0 has no significance - so scan forward from BOB to see how
!     ;; nested point is, then carry on from there.
!     (let* ((floor (point-min))
! 	   (ceiling (point-max))
! 	   (pps-state (let (syntax-begin-function
! 			    font-lock-beginning-of-syntax-function)
! 			(syntax-ppss)))
! 	   (nesting-depth (nth 0 pps-state)))
        (save-restriction
  	(widen)
! 	;; Get outside of any string or comment.
! 	(if (nth 8 pps-state)
! 	    (goto-char (nth 8 pps-state)))
! 
! 	(cond
! 	 ((> arg 0)
! 	  (when (> nesting-depth 0)
! 	    (up-list (- nesting-depth))
! 	    (setq arg (1- arg)))
! 	  ;; We're now outside of any defun.
! 	  (backward-list arg)
! 	  (if (< (point) floor) (goto-char floor)))
! 
! 	 ((< arg 0)
! 	  (cond
! 	   ((> nesting-depth 0)
! 	    (up-list nesting-depth)
! 	    (setq arg (1+ arg)))
! 	   ((not (looking-at "\\s("))
! 	    ;; We're between defuns, and not at the start of one.
! 	    (setq arg (1+ arg))))
! 	  (forward-list (- arg))
! 	  (down-list)
! 	  (backward-char)
! 	  (if (> (point) ceiling) (goto-char ceiling)))))))))

  (defvar end-of-defun-function nil
    "If non-nil, function for function `end-of-defun' to call.
--- 229,263 ----
  			       "^\\s(")
  			     nil 'move arg)
  	 (progn (goto-char (1- (match-end 0)))) t))
     (t
!     (let ((floor (point-min))
! 	  (ceiling (point-max)))
        (save-restriction
  	(widen)
! 	(let* ((ppss (let (syntax-begin-function
! 			   font-lock-beginning-of-syntax-function)
! 		       (syntax-ppss)))
! 	       (pos (or (let ((pos (car (nth 9 ppss))))
! 			  (when pos		; Within defun.
! 			    (when (> arg 0) (setq arg (1- arg)))
! 			    pos))
! 			(nth 8 ppss)		; Within string or comment.
! 			(point))))		; Must be at outermost level.
! 	  (goto-char pos)
! 	  (condition-case nil
! 	      (progn
! 		(forward-list (- arg))
! 		(cond
! 		 ((< pos floor)
! 		  (goto-char floor)
! 		  nil)
! 		 ((> pos ceiling)
! 		  (goto-char ceiling)
! 		  nil)
! 		 (t)))
! 	    (error
! 	     (goto-char (if (< arg 0) ceiling floor))
! 	     nil))))))))

  (defvar end-of-defun-function nil
    "If non-nil, function for function `end-of-defun' to call.

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