Optimize c-crosses-statement-barrier-p for large blocks of comment.

This fixes bug #18134.

* lisp/progmodes/cc-engine.el (c-crosses-statement-barrier-p): Give a limit
to the c-backward-syntactic-ws which is searching for a virtual semicolon.  In
the main loop, Use c-forward-syntactic-ws to skip blocks of comments.

1 files changed, 5 insertions, 1 deletions

diff --git a/lisp/progmodes/cc-engine.el b/lisp/progmodes/cc-engine.el
index 8d92b26ebd0..cceb58c290a 100644
--- a/lisp/progmodes/cc-engine.el
+++ b/lisp/progmodes/cc-engine.el
@@ -1468,10 +1468,14 @@ comment at the start of cc-engine.el for more info."
                      (progn
                        (if (setq lit-start (c-literal-start from)) ; Have we landed in a string/comment?
                            (goto-char lit-start))
-                       (c-backward-syntactic-ws) ; ? put a limit here, maybe?
+                       (c-backward-syntactic-ws (c-point 'bopl))
                        (setq vsemi-pos (point))
                        (c-at-vsemi-p))))
               (throw 'done vsemi-pos))
+             ;; Optimize for large blocks of comments.
+             ((progn (c-forward-syntactic-ws to)
+                     (>= (point) to))
+              (throw 'done nil))
              ;; In a string/comment?
              ((setq lit-range (c-literal-limits from))
               (goto-char (cdr lit-range)))