1 files changed, 13 insertions, 3 deletions

diff --git a/lisp/progmodes/cc-styles.el b/lisp/progmodes/cc-styles.el
index 08b5fae35f6..5d467e669f7 100644
--- a/lisp/progmodes/cc-styles.el
+++ b/lisp/progmodes/cc-styles.el
@@ -570,14 +570,24 @@ offset for that syntactic element.  Optional ADD says to add SYMBOL to
   ;; variables first to the `cc-mode' style before instituting the new
   ;; style.  Only do this once!
   (or (assoc "cc-mode" c-style-alist)
-      (progn
+      (let (copyfunc)
+        ;; use built-in copy-tree if its there.
+        (if (fboundp 'copy-tree)
+            (setq copyfunc (symbol-function 'copy-tree))
+          (setq copyfunc (lambda (tree)
+                            (if (consp tree)
+                                (cons (funcall copyfunc (car tree))
+                                      (funcall copyfunc (cdr tree)))
+                              tree))))
         (c-add-style "cc-mode"
                      (mapcar
                       (function
                        (lambda (var)
                          (let ((val (symbol-value var)))
-                           (cons var (if (atom val) val
-                                       (copy-sequence val)))
+                           (cons var (if (atom val)
+                                         val
+                                       (funcall copyfunc val)
+                                       ))
                            )))
                       '(c-backslash-column
                         c-basic-offset