Re: unwind-protect within while-no-input

[Spencer Baugh <sbaugh@janestreet.com>]

Michael Heerdegen via "Emacs development discussions."
<emacs-devel@gnu.org> writes:

> Spencer Baugh <sbaugh@janestreet.com> writes:
>
>> > #+begin_src emacs-lisp
>> > (let (foo)
>> >   (while-no-input
>> >     (unwind-protect (while t nil)
>> >       (let ((inhibit-quit t))
>> >         (sleep-for 10)
>> >         (setq foo 'interrupted)
>> >         (message "foo: %s" foo)))
>> >     (message "foo: %s" foo)))
>> > #+end_src
>> >
>> > (unwind forms are not per se protected from nonlocal exiting - see
>> > documentation)
>>
>> That seems to work, but is it robust?
>>
>> If while-no-input can raise a quit between the start of executing
>> unwindforms and the binding of inhibit-quit, then the unwind forms will
>> not execute.
>
> AFAIK, unwind forms are always handled, but they can be exited
> nonlocally.  Above there is only one, and is protected, so I guess it is
> save.

That unwind-form is only protected once inhibit-quit is bound.  But at
the start of its evaluation, it is not protected because inhibit-quit is
not bound.  Is it possible for a quit to be raised there, before the
protection starts?

>> Can while-no-input/throw-on-input actually raise a quit then?  And is
>> this behavior documented anywhere?
>
> I don't understand the first question.  The fact that we protect code
> against quitting does not prevent quit being triggered - only in
> which way the stack is unwinded...right?
>
> Michael.