* Re: bug#20352: Factor 2 slow down of font-locking in c-mode
[not found] ` <jwvoamlv8qy.fsf-monnier+emacsbugs@gnu.org>
@ 2015-05-03 21:33 ` Alan Mackenzie
2015-05-04 2:13 ` Stefan Monnier
0 siblings, 1 reply; 3+ messages in thread
From: Alan Mackenzie @ 2015-05-03 21:33 UTC (permalink / raw)
To: Stefan Monnier; +Cc: emacs-devel
Hello, Stefan.
On Sat, Apr 18, 2015 at 10:02:17AM -0400, Stefan Monnier wrote:
> Hmm... I hope comparing the profiler reports will give us a clue.
Indeed. Some while ago, you were musing on putting syntax-ppss, or
equivalent, into syntax.c, thus rendering
open-paren-in-column-0-is-defun-start unnecessary and obsolete. This
would speed up or improve the accuracy of, in particular, back_comment
and the stacks of things which depend upon it.
Is this enhancement still intended?
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: bug#20352: Factor 2 slow down of font-locking in c-mode
2015-05-03 21:33 ` bug#20352: Factor 2 slow down of font-locking in c-mode Alan Mackenzie
@ 2015-05-04 2:13 ` Stefan Monnier
2015-05-04 10:33 ` Alan Mackenzie
0 siblings, 1 reply; 3+ messages in thread
From: Stefan Monnier @ 2015-05-04 2:13 UTC (permalink / raw)
To: Alan Mackenzie; +Cc: emacs-devel
> Indeed. Some while ago, you were musing on putting syntax-ppss, or
> equivalent, into syntax.c, thus rendering
> open-paren-in-column-0-is-defun-start unnecessary and obsolete. This
> would speed up or improve the accuracy of, in particular, back_comment
> and the stacks of things which depend upon it.
> Is this enhancement still intended?
Not in the short term, no. I've toyed with it, but there's a problem:
syntax-ppss's caching relies on the syntax-table being constant.
This usually works fine because the callers "know" to call syntax-ppss
outside of with-syntax-table (I guess in reality they don't really know,
but they happen to do that because they call syntax-ppss fairly early
on), but it's not uncommon for Elisp code (definitely including CC-mode)
to use with-syntax-table around calls to forward-sexp/comment, so
calling syntax-ppss implicitly from within those functions exposes this
underlying syntax-ppss limitation.
IOW, it can't be done until we figure out how to make syntax-ppss handle
syntax-table changes.
Stefan
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: bug#20352: Factor 2 slow down of font-locking in c-mode
2015-05-04 2:13 ` Stefan Monnier
@ 2015-05-04 10:33 ` Alan Mackenzie
0 siblings, 0 replies; 3+ messages in thread
From: Alan Mackenzie @ 2015-05-04 10:33 UTC (permalink / raw)
To: Stefan Monnier; +Cc: emacs-devel
Hello, Stefan.
On Sun, May 03, 2015 at 10:13:48PM -0400, Stefan Monnier wrote:
> > Indeed. Some while ago, you were musing on putting syntax-ppss, or
> > equivalent, into syntax.c, thus rendering
> > open-paren-in-column-0-is-defun-start unnecessary and obsolete. This
> > would speed up or improve the accuracy of, in particular, back_comment
> > and the stacks of things which depend upon it.
> > Is this enhancement still intended?
> Not in the short term, no. I've toyed with it, but there's a problem:
> syntax-ppss's caching relies on the syntax-table being constant.
> This usually works fine because the callers "know" to call syntax-ppss
> outside of with-syntax-table (I guess in reality they don't really know,
> but they happen to do that because they call syntax-ppss fairly early
> on), but it's not uncommon for Elisp code (definitely including CC-mode)
> to use with-syntax-table around calls to forward-sexp/comment, so
> calling syntax-ppss implicitly from within those functions exposes this
> underlying syntax-ppss limitation.
Ah. That sounds like a shame.
> IOW, it can't be done until we figure out how to make syntax-ppss handle
> syntax-table changes.
How about having an association list of ((syntax-table . cache) ...), or
something like that? Each cache would need its own value of the
equivalent of `syntax-propertize--done'. `modify-syntax-entry' would
need to wipe the cache. Then there are `category' text
properties/overlays which might affect the syntax. And so on. And so
on.
OK. It's difficult.
> Stefan
--
Alan Mackenzie (Nuremberg, Germany).
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-05-03 21:33 ` bug#20352: Factor 2 slow down of font-locking in c-mode Alan Mackenzie
2015-05-04 2:13 ` Stefan Monnier
2015-05-04 10:33 ` Alan Mackenzie
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