frame-local bindings, makunbound --> halt / CPU hog

[David Reitter]

Start a fresh Emacs (-Q),
open an extra frame with C-x 5 2,
paste the code below into the buffer and then do M-x eval-buffer.

(setq testvar 77) ;; global binding
(print testvar)
(make-variable-frame-local 'testvar)
(modify-frame-parameters nil '((testvar . 33)))  ;; local binding
(print testvar)
(makunbound 'testvar)
(print testvar)


1) You will see that Emacs grinds to a halt, eating up CPU time and  
reacting (if at all) sluggishly and erratically until it's killed.
This occurs during makunbound.
I tested this with a recent CVS Emacs on GNU/Linux (X11), and with  
the Carbon port. Same symptoms.

2)  I think I wasn't using makunbound properly. I confused frame/ 
buffer 'local' variables with variables with local scope in elisp. It  
would be nice if someone could tell me how to unbind frame-local  
variables so that they have global scope again.