Bug in y-or-n-p?

[Richard M. Stallman]

Can someone please debug this?

    From: "Drew Adams" <address@hidden>

    1. Define these:

    (defun foo () (y-or-n-p "foo? "))
    (defun bar () (y-or-n-p "bar? "))
    (setq kill-emacs-query-functions '(foo bar))

    2. Use the menu-bar File > Exit Emacs. 

    The question "foo? " correctly appears in a popup menu y/n.

    3. Respond `n'  to "foo? ".

    4. The question "bar? " should be asked via a popup menu also, but it
       appears instead in the minibuffer.

    That is, the user starts with the mouse and menu-bar, but he is
    obliged to switch mid-stream to answering with the keyboard.

I think something in the C code is setting last_nonmenu_event
in between the two calls to y-or-n-p.  Could someone please
find out what?