Re: [Qemu-devel] [PATCH 07/13] Monitor: handle optional '-' arg as a bool

[Markus Armbruster <armbru@redhat.com>]

Luiz Capitulino <lcapitulino@redhat.com> writes:

> On Wed, 23 Jun 2010 17:05:02 +0200
> Markus Armbruster <armbru@redhat.com> wrote:
>
>> Luiz Capitulino <lcapitulino@redhat.com> writes:
>> 
>> > Historically, user monitor arguments beginning with '-' (eg. '-f')
>> > were passed as integers down to handlers.
>> >
>> > I've maintained this behavior in the new monitor because we didn't
>> > have a boolean type at the very beginning of QMP. Today we have it
>> > and this behavior is causing trouble to QMP's argument checker.
>> >
>> > This commit fixes the problem by doing the following changes:
>> >
>> > 1. User Monitor
>> >
>> >    Before: the optional arg was represented as a QInt, we'd pass 1
>> >            down to handlers if the user specified the argument or
>> >            0 otherwise
>> >
>> >    This commit: the optional arg is represented as a QBool, we pass
>> >                 true down to handlers if the user specified the
>> >                 argument, otherwise _nothing_ is passed
>> >
>> > 2. QMP
>> >
>> >    Before: the client was required to pass the arg as QBool, but we'd
>> >            convert it to QInt internally. If the argument wasn't passed,
>> >            we'd pass 0 down
>> >
>> >    This commit: still require a QBool, but doesn't do any conversion and
>> >                 doesn't pass any default value
>> >
>> > 3. Convert existing handlers (do_eject()/do_migrate()) to the new way
>> >
>> >    Before: Both handlers would expect a QInt value, either 0 or 1
>> >
>> >    This commit: Change the handlers to accept a QBool, they handle the
>> >                 following cases:
>> >
>> >                    A) true is passed: the option is enabled
>> >                    B) false is passed: the option is disabled
>> >                    C) nothing is passed: option not specified, use
>> >                                          default behavior
>> 
>> Because the user monitor can't pass false, the only sensible default
>> behavior is "disabled".
>
> Yes, but I think we shouldn't impose it. I mean, handlers are still free
> to choose an 'enabled' default state.

They are.  Renders the option entirely useless in the user monitor,
though.

I don't want you to change anything, I just wanted to point out that the
human monitor can't yet support boolean arguments defaulting to true.
QMP can, of course.