Re: [Qemu-devel] Re: [RFC][PATCH v1 05/12] qapi: fix handling for null-return async callbacks

[Anthony Liguori]

On 03/28/2011 12:06 PM, Luiz Capitulino wrote:
> On Mon, 28 Mar 2011 12:01:16 -0500
> Anthony Liguori<address@hidden>  wrote:
>
> > On 03/28/2011 11:47 AM, Luiz Capitulino wrote:
> > > On Fri, 25 Mar 2011 16:22:16 -0500
> > > Anthony Liguori<address@hidden>   wrote:
> > >
> > > > On 03/25/2011 02:47 PM, Michael Roth wrote:
> > > > > Async commands like 'guest-ping' have NULL retvals. Handle these by
> > > > > inserting an empty dictionary in the response's "return" field.
> > > > >
> > > > > Signed-off-by: Michael Roth<address@hidden>
> > > > > ---
> > > > >     qmp-core.c |    5 ++++-
> > > > >     1 files changed, 4 insertions(+), 1 deletions(-)
> > > > >
> > > > > diff --git a/qmp-core.c b/qmp-core.c
> > > > > index e33f7a4..9f3d182 100644
> > > > > --- a/qmp-core.c
> > > > > +++ b/qmp-core.c
> > > > > @@ -922,9 +922,12 @@ void qmp_async_complete_command(QmpCommandState *cmd, 
> > > > > QObject *retval, Error *er
> > > > >         rsp = qdict_new();
> > > > >         if (err) {
> > > > >             qdict_put_obj(rsp, "error", error_get_qobject(err));
> > > > > -    } else {
> > > > > +    } else if (retval) {
> > > > >             qobject_incref(retval);
> > > > >             qdict_put_obj(rsp, "return", retval);
> > > > > +    } else {
> > > > > +        /* add empty "return" dict, this is the standard for NULL returns */
> > > > > +        qdict_put_obj(rsp, "return", QOBJECT(qdict_new()));
> > > > Luiz, I know we decided to return empty dicts because it lets us extend
> > > > things better, but did we want to rule out the use of a 'null' return
> > > > value entirely?
> > > For asynchronous commands you mean? No we didn't.
> > No, nothing to do with asynchronous commands.  Just in general.
> >
> > The question is, is it legal for a command to return 'null'.  It's
> > certain valid JSON, but is it valid QMP?
> No, it's not valid.

Do we have a reason for this?

Regards,

Anthony Liguori