Re: [Qemu-devel] [PATCH 0/6] refactor PC machine, i440fx and piix3 to take advantage of QOM

[Anthony Liguori <anthony@codemonkey.ws>]

On 03/26/2012 03:30 PM, Jan Kiszka wrote:
> On 2012-03-26 22:13, Anthony Liguori wrote:
>> On 03/26/2012 03:10 PM, Jan Kiszka wrote:
>>> On 2012-03-26 21:49, Anthony Liguori wrote:
>>>> On 03/26/2012 02:44 PM, Jan Kiszka wrote:
>>>> This would also mean that reference counting should be revisited
>>>> although with how dereferencing a parent affects the child.
>>>>
>>>> It's not rocket science, but it's also something that needs to be done
>>>> carefully.
>>>
>>> But all this is only a problem for these three here (PIT, RTC, HPET) as
>>> their objects shall be embedded into the super-IO. If you only embed an
>>> object pointer, it shouldn't be an issue anymore, no?
>>
>> The reference counting stuff obviously needs to be looked at even in
>> this case.
>
> A composite object is owned by its container. So it should go when the
> container leaves.

It's more complicated than that because it's a tree, not a graph.  So there may 
be additional references held beyond the parent.

>>> Also inheritance is not a problem here as we do not derive from the
>>> three types in question. If there is a super/sub-class relation, those
>>> need to share an internal header, of course.
>>
>> Yes, but then you have two headers for every type.  Is that really a
>> good thing?
>
> It's cleaner and more explicit than tagging members with comments. And
> it's nothing we will have for each and every type as only a small subset
> is actually inheriting, the mass is finalizing.

I don't fundamentally disagree with anything you're saying here.  I'm only 
pointing out that (1) it's not a trivial problem and (2) it's not an urgent problem.

Regards,

Anthony Liguori

>
> Jan