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Date: Fri, 25 Mar 2011 16:22:16 -0500
From: Anthony Liguori <aliguori@us.ibm.com>
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Subject: [Qemu-devel] Re: [RFC][PATCH v1 05/12] qapi: fix handling for
 null-return async callbacks
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To: Michael Roth <mdroth@linux.vnet.ibm.com>
Cc: aliguori@linux.vnet.ibm.com, Luiz Capitulino <lcapitulino@redhat.com>, agl@linux.vnet.ibm.com, qemu-devel@nongnu.org, Jes.Sorensen@redhat.com

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<mdroth@linux.vnet.ibm.com>
> ---
>   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 a command like this, I can't imagine ever wanting to extend the 
return value...

Regards,

Anthony Liguori

>       }
>       if (cmd->tag) {
>           qdict_put_obj(rsp, "tag", cmd->tag);