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Date: Mon, 02 Dec 2013 14:48:01 +0800
From: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
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Subject: Re: [Qemu-devel] [PATCH RFC 2/3] qapi script: add support of event
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To: Luiz Capitulino <lcapitulino@redhat.com>
Cc: kwolf@redhat.com, pbonzini@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com, mdroth@linux.vnet.ibm.com


>>
>>>> +
>>>> +    if (!qapi_event_functions.emit) {
>>>
>>> Better to return an error here instead of silently failing.
>>>
>>
>>     The purpose is allowing emit=NULL and skip event code in that case.
>
> But the code will do nothing and the caller won't know that.
>
   Now the caller also won't know that useless code will be executed,
when qemu-img link with stub of monitor_event functions. :)

> Actually, I wonder if the code should even abort() in such a case,
> as emit=NULL would be a programming today.
>

   I am not sure why the code should always do something. The code may
actually take CPU resource to do nothing meanful, such as build up a
qdict and release it later, when emit is not a valid function. So I
did this as an improvement: check emit function ahead to escape useless
work.