CC Mode: Fix unstable fontification of doc strings.

Also optimize a loop over several line doc-comments.

* lisp/progmodes/cc-fonts.el (c-font-lock-doc-comments): New variable
comment-mid, used as the starting point for applying c-doc-face-name in a
line comments.  In block comments, apply this face not from `comment-beg' but
from `region-beg', no earlier than the start of the fontification region.

1 files changed, 9 insertions, 6 deletions

diff --git a/lisp/progmodes/cc-fonts.el b/lisp/progmodes/cc-fonts.el
index fd00d65e335..5f3e2eaaf80 100644
--- a/lisp/progmodes/cc-fonts.el
+++ b/lisp/progmodes/cc-fonts.el
@@ -2733,13 +2733,14 @@ need for `pike-font-lock-extra-types'.")
   ;;
   ;; This function might do hidden buffer changes.
 
-  (let (comment-beg region-beg)
+  (let (comment-beg region-beg comment-mid)
     (if (memq (get-text-property (point) 'face)
               '(font-lock-comment-face font-lock-comment-delimiter-face))
         ;; Handle the case when the fontified region starts inside a
         ;; comment.
         (let ((start (c-literal-start)))
-          (setq region-beg (point))
+          (setq region-beg (point)
+                comment-mid (point))
           (when start
             (goto-char start))
           (when (looking-at prefix)
@@ -2765,7 +2766,8 @@ need for `pike-font-lock-extra-types'.")
                                 (goto-char comment-beg)
                                 (c-in-literal)))))
               (setq comment-beg nil))
-            (setq region-beg comment-beg))
+            (setq region-beg comment-beg
+                  comment-mid comment-beg))
 
       (if (elt (parse-partial-sexp comment-beg (+ comment-beg 2)) 7)
           ;; Collect a sequence of doc style line comments.
@@ -2773,15 +2775,16 @@ need for `pike-font-lock-extra-types'.")
             (goto-char comment-beg)
             (while (and (progn
                           (c-forward-single-comment)
-                          (c-put-font-lock-face comment-beg (point)
+                          (c-put-font-lock-face comment-mid (point)
                                                 c-doc-face-name)
                           (skip-syntax-forward " ")
-                          (setq comment-beg (point))
+                          (setq comment-beg (point)
+                                comment-mid (point))
                           (< (point) limit))
                         (looking-at prefix))))
         (goto-char comment-beg)
         (c-forward-single-comment)
-        (c-put-font-lock-face comment-beg (point) c-doc-face-name))
+        (c-put-font-lock-face region-beg (point) c-doc-face-name))
       (if (> (point) limit) (goto-char limit))
       (setq comment-beg nil)