Amend c-backward-sws better to handle multiline block comments

In particular, multiline comments lacking escaped newlines.

* lisp/progmodes/cc-engine.el (c-backward-sws): Whilst searching backward for
a putative beginning of macro, move back over block comments whose innards
lack escaped newlines.

1 files changed, 27 insertions, 8 deletions

diff --git a/lisp/progmodes/cc-engine.el b/lisp/progmodes/cc-engine.el
index 0964c04b899..0c338fa3868 100644
--- a/lisp/progmodes/cc-engine.el
+++ b/lisp/progmodes/cc-engine.el
@@ -327,6 +327,8 @@ comment at the start of cc-engine.el for more info."
           (when (or (null lim)
                     (>= here lim))
             (save-match-data
+              ;; Note the similarity of the code here to some in
+              ;; `c-backward-sws'.
               (while
                   (progn
                     (while (eq (char-before (1- (point))) ?\\)
@@ -2461,17 +2463,34 @@ comment at the start of cc-engine.el for more info."
                    (/= cmt-skip-pos simple-ws-beg)
                    (c-beginning-of-macro))
               ;; Inside a cpp directive.  See if it should be skipped over.
-              (let ((cpp-beg (point)))
+              (let ((cpp-beg (point))
+                    pause pos)
 
-                ;; Move back over all line continuations in the region skipped
-                ;; over by `c-backward-comments'.  If we go past it then we
-                ;; started inside the cpp directive.
+                ;; Move back over all line continuations and block comments in
+                ;; the region skipped over by `c-backward-comments'.  If we go
+                ;; past it then we started inside the cpp directive.
                 (goto-char simple-ws-beg)
                 (beginning-of-line)
-                (while (and (> (point) cmt-skip-pos)
-                            (progn (backward-char)
-                                   (eq (char-before) ?\\)))
-                  (beginning-of-line))
+                ;; Note the similarity of the code here to some in
+                ;; `c-beginning-of-macro'.
+                (setq pause (point))
+                (while
+                    (progn
+                      (while (and (> (point) cmt-skip-pos)
+                                  (progn (backward-char)
+                                         (eq (char-before) ?\\)))
+                        (beginning-of-line))
+                      (setq pos (point))
+                      (when (and c-last-c-comment-end-on-line-re
+                                 (re-search-forward
+                                  c-last-c-comment-end-on-line-re pause t))
+                        (goto-char (match-end 1))
+                        (if (c-backward-single-comment)
+                            (progn
+                              (beginning-of-line)
+                              (setq pause (point)))
+                          (goto-char pos)
+                          nil))))
 
                 (if (< (point) cmt-skip-pos)
                     ;; Don't move past the cpp directive if we began inside