Fix a loop in c-fl-decl-start. This fixes bug #34186.

* lisp/progmodes/cc-mode.el (c-fl-decl-start) In the pair of operations
c-syntactic-skip-backward and c-forward-syntactic-ws, ensure the latter
doesn't come back to the position before the former, and break out of the
enclosing loop if it does.

1 files changed, 3 insertions, 0 deletions

diff --git a/lisp/progmodes/cc-mode.el b/lisp/progmodes/cc-mode.el
index 8cbb4e86123..5283cfea6eb 100644
--- a/lisp/progmodes/cc-mode.el
+++ b/lisp/progmodes/cc-mode.el
@@ -1487,6 +1487,7 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
   ;; lock context (etc.) fontification.
   (goto-char pos)
   (let ((lit-start (c-literal-start))
+        old-pos
         (new-pos pos)
         capture-opener
         bod-lim bo-decl)
@@ -1509,12 +1510,14 @@ Note that this is a strict tail, so won't match, e.g. \"0x....\".")
     (while
         ;; Go to a less nested declaration each time round this loop.
         (and
+         (setq old-pos (point))
          (c-syntactic-skip-backward "^;{}" bod-lim t)
          (> (point) bod-lim)
          (progn (c-forward-syntactic-ws)
                 ;; Have we got stuck in a comment at EOB?
                 (not (and (eobp)
                           (c-literal-start))))
+         (< (point) old-pos)
          (progn (setq bo-decl (point))
                 (or (not (looking-at c-protection-key))
                     (c-forward-keyword-clause 1)))