X-Git-Url: http://repo.macrolet.net/gitweb/?a=blobdiff_plain;f=src%2Fcode%2Flist.lisp;h=da6ca8e60a30b7c9c8b17894fe4dd9b973dc37f7;hb=0395c15ff8394bfaaed03050c1a7a131f197a732;hp=d74cc1c48a3e54b886e3fb2d82407fdbd4b29d02;hpb=372d68ae1432a96a527c662de3af3bb334808856;p=sbcl.git

diff --git a/src/code/list.lisp b/src/code/list.lisp
index d74cc1c..da6ca8e 100644
--- a/src/code/list.lisp
+++ b/src/code/list.lisp
@@ -445,8 +445,21 @@
   #!+sb-doc
   "Recursively copy trees of conses."
   (if (consp object)
-      (cons (copy-tree (car object)) (copy-tree (cdr object)))
+      (let ((result (list (if (consp (car object))
+                              (copy-tree (car object))
+                              (car object)))))
+        (loop for last-cons = result then new-cons
+              for cdr = (cdr object) then (cdr cdr)
+              for car = (if (consp cdr)
+                            (car cdr)
+                            (return (setf (cdr last-cons) cdr)))
+              for new-cons = (list (if (consp car)
+                                       (copy-tree car)
+                                       car))
+              do (setf (cdr last-cons) new-cons))
+        result)
       object))
+
 
 ;;;; more commonly-used list functions