bug#4030: forward-sexp parses character literal ?; as comment

[martin rudalics <rudalics@gmx.at>]

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 > Yes, but we need to do that even on chunks of code that have not yet
 > been (and may never be) displayed and in buffers where font-lock
 > is disabled.  IOW I'm not talking about fontification but about parsing.

Sure.  But I was only talking about the possibility to highlight such
instances just like we do with column 0 parens in strings already.

 > Pretty much, yes, tho the error message should give more info (the OP
 > complained about lack of info in the error message).

That's what the ellipsis stands for.  But what info?  Guessing a good
buffer position seems next to impossible.  Where else can `forward-sexp'
go astray when called from a top-level position?

 >> But do we really have to scan the buffer in the first place?
 >
 > Don't know.  Maybe not, indeed.  Maybe it's just to detect the "too many
 > closing parens" case as well (i.e. rather than silently ignore trailing
 > code).

We could simply search for (concat "^(" (symbol-name symbol))) and do a
`forward-sexp' over the form starting there as in the attached patch.  I
see no reason why we should try to handle an .emacs broken before or
after that form.

martin

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*** cus-edit.el.~1.364.~	2009-07-27 08:09:05.997162900 +0200
--- cus-edit.el	2009-08-11 10:51:21.812500000 +0200
***************
*** 4338,4374 ****
  
  This function does not save the buffer."
    (goto-char (point-min))
!   ;; Skip all whitespace and comments.
!   (while (forward-comment 1))
!   (or (eobp)
!       (save-excursion (forward-sexp (buffer-size)))) ; Test for scan errors.
!   (let (first)
!     (catch 'found
!       (while t ;; We exit this loop only via throw.
! 	;; Skip all whitespace and comments.
! 	(while (forward-comment 1))
! 	(let ((start (point))
! 	      (sexp (condition-case nil
! 			(read (current-buffer))
! 		      (end-of-file (throw 'found nil)))))
! 	  (when (and (listp sexp)
! 		     (eq (car sexp) symbol))
! 	    (delete-region start (point))
! 	    (unless first
! 	      (setq first (point)))))))
!     (if first
! 	(goto-char first)
!       ;; Move in front of local variables, otherwise long Custom
!       ;; entries would make them ineffective.
!       (let ((pos (point-max))
! 	    (case-fold-search t))
! 	(save-excursion
! 	  (goto-char (point-max))
! 	  (search-backward "\n\^L" (max (- (point-max) 3000) (point-min))
! 			   'move)
! 	  (when (search-forward "Local Variables:" nil t)
! 	    (setq pos (line-beginning-position))))
! 	(goto-char pos)))))
  
  (defun custom-save-variables ()
    "Save all customized variables in `custom-file'."
--- 4338,4364 ----
  
  This function does not save the buffer."
    (goto-char (point-min))
!   (if (re-search-forward (concat "^(" (symbol-name symbol)))
!       (let ((from (goto-char (match-beginning 0)))
! 	    (to (condition-case nil
! 		    (progn
! 		      (forward-sexp)
! 		      (point))
! 		  (error nil))))
! 	(if to
! 	    (delete-region from to)
! 	  (error "Malformed %s expression" symbol)))
!     ;; Move in front of local variables, otherwise long Custom
!     ;; entries would make them ineffective.
!     (let ((pos (point-max))
! 	  (case-fold-search t))
!       (save-excursion
! 	(goto-char (point-max))
! 	(search-backward "\n\^L" (max (- (point-max) 3000) (point-min))
! 			 'move)
! 	(when (search-forward "Local Variables:" nil t)
! 	  (setq pos (line-beginning-position))))
!       (goto-char pos))))
  
  (defun custom-save-variables ()
    "Save all customized variables in `custom-file'."