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bug#16526: 24.3.50; scroll-conservatively & c-mode regression
From: |
Alan Mackenzie |
Subject: |
bug#16526: 24.3.50; scroll-conservatively & c-mode regression |
Date: |
Wed, 29 Jan 2014 22:36:27 +0000 |
User-agent: |
Mutt/1.5.21 (2010-09-15) |
Hi, Martin.
On Mon, Jan 27, 2014 at 09:21:24AM +0100, martin rudalics wrote:
> > The @dfn{state cache}, a list of certain brace/paren/bracket positions
> > around some position, is set for a position near EOB. With the switch to
> > a different position, CC Mode tweaks the state cache rather than
> > calculating it anew starting at BOB. When the new position is nearer
> > BOB, the code searches backwards for the appropriate braces. However, it
> > shouldn't be scanning the entire buffer backwards. There is clearly a
> > bug here.
> In my scenario `end-of-buffer' should already have produced the complete
> state cache. How else would you have been able to fontify code near EOB
> correctly?
The state cache contains not only a list of enclosing
braces/brackets/parentheses but also any brace pair immediately
preceding one of these things. So a typical state cache looks like:
(4532 (4284 . 4526) 4278 (4131 . 4248))
(with a detailed explanation in cc-engine.el in the comment for
`c-parse-state-1').
When c-parse-state is called at a position somewhat distant from the
previous call, it modifies the state cache by crawling through the
buffer rather than recalculating it from scratch.
> > The backward scan-lists calls will be causing continual forward searches
> > from BOB in syntax.c, every time the backward scan hits a comment ender.
> IIUC now any call to `forward-comment' with a negative argument will
> automatically go to BOB unless it's already there. How else could it
> determine that it's not called from a position within a comment?
I don't think this happens. back_comment (in syntax.c) assumes it
starts outside a comment.
> So if you decide to bind `open-paren-in-column-0-is-defun-start' to
> nil, then why don't you build the state cache anew from BOB?
The state cache has different values for different buffer positions.
> In any case, please provide an option say
> `c-open-paren-in-column-0-is-defun-start' which people can set to
> avoid those scans. The doc-string should mention that things like
> Michael's commented out code are handled correctly iff this option is
> nil and that long delays while working with c-mode can be sometimes
> avoided by setting this option to t. The default value could be
> obviously nil.
I'm hoping that the (rough) patch in one of my other emails from this
evening will have solved the bug, so that playing around with
open-paren-in-column-0-etc. won't be needed.
As a matter of interest, with my patch applied, running your recipe on
xdisp.c took me 4.4 seconds (including the (sit-for 3)).
> martin
--
Alan Mackenzie (Nuremberg, Germany).
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, (continued)
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/25
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/25
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/25
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/26
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/26
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Alan Mackenzie, 2014/01/26
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/27
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Stefan Monnier, 2014/01/27
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/27
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Stefan Monnier, 2014/01/27
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression,
Alan Mackenzie <=
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/30
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/30
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/30
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/30
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Alan Mackenzie, 2014/01/29
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/30
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Alan Mackenzie, 2014/01/31
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/31
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, martin rudalics, 2014/01/27
- bug#16526: 24.3.50; scroll-conservatively & c-mode regression, Eli Zaretskii, 2014/01/27