gnus-util.el (gnus-macroexpand-all): Don't modify argument.

2 files changed, 5 insertions, 1 deletions

diff --git a/lisp/gnus/ChangeLog b/lisp/gnus/ChangeLog
index acd0ac18571..85c8434a7e8 100644
--- a/lisp/gnus/ChangeLog
+++ b/lisp/gnus/ChangeLog
@@ -1,3 +1,7 @@
+2010-12-03  Katsumi Yamaoka  <yamaoka@jpl.org>
+
+        * gnus-util.el (gnus-macroexpand-all): Don't modify argument.
+
 2010-12-03  Glenn Morris  <rgm@gnu.org>
 
         * mm-extern.el (message-goto-body): Update declaration.
diff --git a/lisp/gnus/gnus-util.el b/lisp/gnus/gnus-util.el
index af5159ece3b..1f391f0cc0c 100644
--- a/lisp/gnus/gnus-util.el
+++ b/lisp/gnus/gnus-util.el
@@ -2041,7 +2041,7 @@ Same as `string-match' except this function does not change the match data."
 If no macros are expanded, FORM is returned unchanged."
     (if (consp form)
         (let ((idx 1)
-              (len (length form))
+              (len (length (setq form (copy-sequence form))))
               expanded)
           (while (< idx len)
             (setcar (nthcdr idx form) (gnus-macroexpand-all (nth idx form)))