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Date: Tue, 02 Jul 2013 08:36:11 +0200
From: Laszlo Ersek <lersek@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v4 08/10] qemu-ga: call Windows VSS
 requester in fsfreeze command handler
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To: Tomoki Sekiyama <tomoki.sekiyama@hds.com>
Cc: "libaiqing@huawei.com" <libaiqing@huawei.com>, "mdroth@linux.vnet.ibm.com" <mdroth@linux.vnet.ibm.com>, "stefanha@gmail.com" <stefanha@gmail.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "lcapitulino@redhat.com" <lcapitulino@redhat.com>, "vrozenfe@redhat.com" <vrozenfe@redhat.com>, "pbonzini@redhat.com" <pbonzini@redhat.com>, Seiji Aguchi <seiji.aguchi@hds.com>, "areis@redhat.com" <areis@redhat.com>

On 07/01/13 19:59, Tomoki Sekiyama wrote:
> On 7/1/13 9:29 , "Laszlo Ersek" <lersek@redhat.com> wrote:
> 
>>> +error:
>>> +    qmp_guest_fsfreeze_thaw(NULL);
>>
>> Passing NULL here as "errp" concerns me slightly. I've been assuming
>> that "errp" is never NULL due to the outermost QMP layer always wanting
>> to receive errors and to serialize them.
>>
>> Specifically, a NULL "errp" would turn all error_set*(errp, ...) calls
>> into no-ops under qmp_guest_fsfreeze_thaw(), and all error_is_set(errp)
>> questions would answer with false. That said, nothing seems to be
>> affected right now.
>>
>> Maybe a dummy local variable would be more future-proof... OTOH it would
>> be stylistically questionable :)
> 
> OK, then it should be:
>     Error *local_err = NULL;
> ...
> error:
>     qmp_guest_fsfreeze_thaw(&local_err);
>     if (error_is_set(&local_err)) {
>         error_free(local_err);
>     }

I think so, yes.

You could also log it before freeing it I guess:

    g_debug("cleanup thaw: %s", error_get_pretty(local_err));

or some such, but it's probably not important.

Thanks,
Laszlo