Re: C mode too slow

[Alan Mackenzie]

Hi, Stefan,

On Sun, Jun 12, 2011 at 08:38:11PM +0000, Alan Mackenzie wrote:

> >> _and_ because editing lisp.h is virtually impossible these days.  I
> >> have to use an old Emacs - almost each editing step takes about 15
> >> secs here with the more recent Emacs versions :-(

> > I tend to find editing code such as lisp.h too slow as well.  Can we
> > do something about it?

> lisp.h is slow in "brace desserts", since CC Mode uses braces as anchor
> points, particularly whilst font locking.  This should have been fixed
> by the optimisation of c-parse-state.

> However, comparing the trunk with Emacs 23.3 the number of calls to
> c-parse-state has increased by a factor of ~9, cancelling out the
> optimisation.  :-(  I'm looking to see why this has happened.

> I'm actually looking at a large file (without a single brace) called
> AT91SAM9263_INC.h, the one which triggered this optimisation.  What
> seems to me slow in lisp.h is scrolling over areas which haven't yet
> been fontified since loading.  Once that is done, I think things move at
> a decent speed.  Is there anything particular, other than initial
> scrolling, which is very slow in lisp.h?

Could you try editing lisp.h after applying this patch, please, and let
me know how it goes:



*** cc-fonts.el.~7~     2011-02-04 22:10:01.000000000 +0000
--- cc-fonts.el 2011-06-13 14:49:30.000000000 +0000
***************
*** 1192,1198 ****
                ;; Are we at a declarator?  Try to go back to the declaration
                ;; to check this.  Note that `c-beginning-of-decl-1' is slow,
                ;; so we cache its result between calls.
!               (let (paren-state bod-res encl-pos is-typedef)
                  (goto-char start-pos)
                  (save-excursion
                    (unless (and decl-search-lim
--- 1192,1200 ----
                ;; Are we at a declarator?  Try to go back to the declaration
                ;; to check this.  Note that `c-beginning-of-decl-1' is slow,
                ;; so we cache its result between calls.
!               (let (paren-state bod-res encl-pos is-typedef
!                                 c-recognize-knr-p) ; Strictly speaking bogus,
!                                       ; but it speeds lisp.h up tremendously.
                  (goto-char start-pos)
                  (save-excursion
                    (unless (and decl-search-lim


-- 
Alan Mackenzie (Nuremberg, Germany).