Normalize SIDE argument of split-window (Bug#8916).

* window.el (split-window): Normalize SIDE argument (Bug#8916).

2 files changed, 6 insertions, 1 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index e5c2e2ad628..0c72fbf47db 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -8,6 +8,7 @@
         * window.el (display-buffer-default-specifiers)
         (display-buffer-alist): Remove entries for pop-up-frame-alist.
         Suggested by Katsumi Yamaoka <yamaoka@jpl.org>.
+        (split-window): Normalize SIDE argument (Bug#8916).
 
         * frame.el (pop-up-frame-alist, pop-up-frame-function)
         (special-display-frame-alist, special-display-popup-frame):
diff --git a/lisp/window.el b/lisp/window.el
index 1c347c70067..ac43fe7703c 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -3014,7 +3014,11 @@ new window are inherited from the window selected on WINDOW's
 frame.  The selected window is not changed by this function."
   (interactive "i")
   (setq window (normalize-any-window window))
-  (let* ((horizontal (not (memq side '(nil below above))))
+  (let* ((side (cond
+                ((not side) 'below)
+                ((memq side '(below above right left)) side)
+                (t 'right)))
+         (horizontal (not (memq side '(nil below above))))
          (frame (window-frame window))
          (parent (window-parent window))
          (function (window-parameter window 'split-window))