From: Alan Mackenzie <acm@muc.de>
To: Stefan Monnier <monnier@iro.umontreal.ca>
Cc: 10664@debbugs.gnu.org
Subject: bug#10664: 24.0.93; JIT font-lock infloops in a C file
Date: Wed, 8 Feb 2012 11:47:49 +0000 [thread overview]
Message-ID: <20120208114749.GA3523@acm.acm> (raw)
In-Reply-To: <jwvpqdq1afl.fsf-monnier+emacs@gnu.org>
Hi, Stefan.
On Tue, Feb 07, 2012 at 06:39:11PM -0500, Stefan Monnier wrote:
> > For one particular fontification in socket.c, the "safe position" is 500
> > bytes back from the starting point, so jit-lock is pushed back these 500
> > bytes, fontifies the next 500 bytes (`jit-lock-chunk-size'), then has its
> > new start position set back 500 bytes, rinse, spin, repeat.
> Why is "jit-lock pushed back"?
Build Emacs revision #106728. emacs -Q, then create the following C++
buffer:
#########################################################################
1 template <typename T>
2
3
4 void myfunc(T* p) {}
#########################################################################
This is fontified correctly. Type a space on L2. This is OK for half a
second, then context fontification messes up L4. The correct
fontification can only be restored by a change to L4.
Revision #106729 fixes this problem, after a space on L2, by making the
fontification start at L1 rather than L2.
The exact mechanism of why the problem happened is buried in my log, and
I could dredge it up if you're really interested.
The problem with this approach is demonstrated in Eli's socket.c:
SCM_DEFINE (scm_inet_pton, "inet-pton", 2, 0, 0,
(SCM family, SCM address),
"Convert a string containing a printable network address to\n"
"an integer address. Note that unlike the C version of this\n"
"function,\n"
"the result is an integer with normal host byte ordering.\n"
"@var{family} can be @code{AF_INET} or @code{AF_INET6}. E.g.,\n\n"
"@lisp\n"
"(inet-pton AF_INET \"127.0.0.1\") @result{} 2130706433\n"
"(inet-pton AF_INET6 \"::1\") @result{} 1\n"
"@end lisp")
#define FUNC_NAME s_scm_inet_pton
{
A 500 byte chunk of fontification ends just before "@end lisp". For
this line, the start of the next chunk is "pushed back" to the
SCM_DEFINE line to get a proper context for "@end lisp". It then
repeatedly fontifies the same chunk.
Interestingly, EOL just before "@end lisp" is exactly 500 bytes after
the initial scm_inet_pton.
--
Alan Mackenzie (Nuremberg, Germany).
next prev parent reply other threads:[~2012-02-08 11:47 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-30 18:23 bug#10664: 24.0.93; JIT font-lock infloops in a C file Eli Zaretskii
2012-02-05 18:18 ` Eli Zaretskii
2012-02-06 11:09 ` Alan Mackenzie
2012-02-06 14:39 ` Stefan Monnier
2012-02-06 17:04 ` Eli Zaretskii
2012-02-07 17:30 ` Eli Zaretskii
2012-02-07 19:20 ` Alan Mackenzie
2012-02-07 20:58 ` Eli Zaretskii
2012-02-07 21:34 ` Alan Mackenzie
2012-02-07 23:39 ` Stefan Monnier
2012-02-08 11:47 ` Alan Mackenzie [this message]
2012-02-08 17:49 ` Eli Zaretskii
2012-02-08 19:28 ` Stefan Monnier
2012-02-10 11:28 ` Alan Mackenzie
2012-02-12 20:57 ` Eli Zaretskii
2012-02-14 5:42 ` Chong Yidong
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