Hello, Eli.
On Sun, Nov 06, 2022 at 15:52:33 +0200, Eli Zaretskii wrote:
> Date: Sun, 06 Nov 2022 09:18:23 +0000
> From: Gregory Heytings <gregory@heytings.org>
> cc: Eli Zaretskii <eliz@gnu.org>,
> Gerd Möllmann <gerd.moellmann@gmail.com>,
> 59038@debbugs.gnu.org, checker@d6.com, acm@muc.de
> >> That file opens just fine in other modes
> > It also opens fine in c-mode, with global-font-lock-mode disabled.
> Indeed, obviously it's a c-mode font-locking related bug.
> >> Note that this bug has nothing to do with long lines.
> > I imagine that the font-lock issue is related to the line being in
> > excess of 21,000 chars (but general redisplay obviously doesn't have
> > problems with lines this 'small').
> > Reduced to 10,208 chars that file opens instantly under emacs -Q in
> > c-mode with font-lock enabled; but at 10,209 chars it hangs Emacs (I
> > killed it after waiting 4 minutes).
> Interesting, thanks for the bisection!
It's an infloop in c-brace-stack-at.
What happens is that c-brace-stack-at calls c-update-brace-stack with
arguments: (nil 1) 8160 13160. c-update-brace-stack then calls
c-syntactic-re-search-forward, which finds nothing interesting and
returns with point at 13160, but then c-update-brace-stack calls
c-beginning-of-current-token, which returns point back to 8160. And
it goes on and on and on...
Thanks for the debugging.
Alan, what can be done with this?
This:
diff -r 53717eda724c cc-engine.el
--- a/cc-engine.el Sat Oct 29 09:42:47 2022 +0000
+++ b/cc-engine.el Sun Nov 06 16:26:09 2022 +0000
@@ -6177,9 +6177,10 @@
(setq s (cdr s))))
((c-keyword-member kwd-sym 'c-flat-decl-block-kwds)
(push 0 s))))
- ;; The failing `c-syntactic-re-search-forward' may have left us in the
- ;; middle of a token, which might be a significant token. Fix this!
- (c-beginning-of-current-token)
+ (when (> prev-match-pos 1) ; Has the search matched at least once?
+ ;; The failing `c-syntactic-re-search-forward' may have left us in the
+ ;; middle of a token, which might be a significant token. Fix this!
+ (c-beginning-of-current-token))
(cons (point)
(cons bound-<> s)))))
--
Alan Mackenzie (Nuremberg, Germany).