* lisp/subr.el (y-or-n-p): Handle empty prompts.

Fixes: debbugs:14770

2 files changed, 8 insertions, 2 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 2204d474be9..1cf0d190130 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,7 @@
+2013-07-03  Glenn Morris  <rgm@gnu.org>
+
+        * subr.el (y-or-n-p): Handle empty prompts.  (Bug#14770)
+
 2013-05-26  Fabián Ezequiel Gallina  <fgallina@gnu.org>
 
         * progmodes/python.el (python-indent-block-enders): Add break,
diff --git a/lisp/subr.el b/lisp/subr.el
index 88f27c75764..0434e3856f9 100644
--- a/lisp/subr.el
+++ b/lisp/subr.el
@@ -2352,7 +2352,8 @@ is nil and `use-dialog-box' is non-nil."
     (cond
      (noninteractive
       (setq prompt (concat prompt
-                           (if (eq ?\s (aref prompt (1- (length prompt))))
+                           (if (or (zerop (length prompt))
+                                   (eq ?\s (aref prompt (1- (length prompt)))))
                                "" " ")
                            "(y or n) "))
       (let ((temp-prompt prompt))
@@ -2369,7 +2370,8 @@ is nil and `use-dialog-box' is non-nil."
             (x-popup-dialog t `(,prompt ("Yes" . act) ("No" . skip)))))
      (t
       (setq prompt (concat prompt
-                           (if (eq ?\s (aref prompt (1- (length prompt))))
+                           (if (or (zerop (length prompt))
+                                   (eq ?\s (aref prompt (1- (length prompt)))))
                                "" " ")
                            "(y or n) "))
       (while