From: Stefan Monnier <monnier@iro.umontreal.ca>
To: Alan Mackenzie <acm@muc.de>
Cc: emacs-devel@gnu.org
Subject: Re: bug#20352: Factor 2 slow down of font-locking in c-mode
Date: Sun, 03 May 2015 22:13:48 -0400 [thread overview]
Message-ID: <jwvd22h3xh9.fsf-monnier+emacsbugs@gnu.org> (raw)
In-Reply-To: <20150503213303.GA4997@acm.fritz.box> (Alan Mackenzie's message of "Sun, 3 May 2015 21:33:03 +0000")
> 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
next prev parent reply other threads:[~2015-05-04 2:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-17 1:41 bug#20352: Factor 2 slow down of font-locking in c-mode Stefan Monnier
[not found] ` <mailman.852.1429234928.904.bug-gnu-emacs@gnu.org>
2015-04-17 19:10 ` Alan Mackenzie
[not found] ` <jwv618uukei.fsf-monnier+emacsbugs@gnu.org>
[not found] ` <20150418094552.GA4182@acm.fritz.box>
2015-04-18 17:32 ` Alan Mackenzie
[not found] ` <jwvoamlv8qy.fsf-monnier+emacsbugs@gnu.org>
2015-05-03 21:33 ` Alan Mackenzie
2015-05-04 2:13 ` Stefan Monnier [this message]
2015-05-04 10:33 ` Alan Mackenzie
2016-05-16 17:28 ` Paul Eggert
2016-05-17 9:05 ` Alan Mackenzie
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