Re: C++ mode and c-beginning-of-current-token

[Kenichi Handa <handa@m17n.org>]

In article <jwvk5v4c0bh.fsf-monnier+emacs@gnu.org>, Stefan Monnier <monnier@iro.umontreal.ca> writes:

> > There are two bugs with identical structure - one in `skip_chars' and
> > one in `scan_words'.

> I have just installed a patch in EMACS_22_BASE for skip_chars.

Thank you.  I've just installed the corresponding change in
emacs-unicode-2.

> As for scan_words, I don't know of such a bug.  Also looking at the code,
> I don't see it (not that it proves anything, of course).  Could you tell me
> where's the problem in scan_words?

martin rudalics <rudalics@gmx.at> writes:
> With Emacs -Q define foo as

> (defun foo ()
>    (interactive)
>    (put-text-property (1- (point)) (point) 'syntax-table '(2))
>    (setq parse-sexp-lookup-properties t))

> open a text-mode buffer, insert a couple of non-word chars in the
> buffer, leave point after them, and type M-x foo followed by M-b.  It
> goes back by _two_ characters instead of one.  The attached patch was
> supposed to fix this and the other problem.

I confirmed this bug.  It seems that the following single
line change is easier to understand what was wrong, but
Martin's change makes the resulting code easier to read.

*** syntax.c	21 May 2007 21:21:30 +0900	1.205
--- syntax.c	21 May 2007 21:53:50 +0900	
***************
*** 1281,1287 ****
  	  if (from == beg)
  	    break;
  	  temp_byte = dec_bytepos (from_byte);
! 	  UPDATE_SYNTAX_TABLE_BACKWARD (from);
  	  ch0 = FETCH_CHAR (temp_byte);
  	  code = SYNTAX (ch0);
  	  if (!(words_include_escapes
--- 1281,1287 ----
  	  if (from == beg)
  	    break;
  	  temp_byte = dec_bytepos (from_byte);
! 	  UPDATE_SYNTAX_TABLE_BACKWARD (from - 1);
  	  ch0 = FETCH_CHAR (temp_byte);
  	  code = SYNTAX (ch0);
  	  if (!(words_include_escapes

---
Kenichi Handa
handa@m17n.org