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Date: Mon, 23 Aug 2010 09:47:46 -0500
From: Anthony Liguori <anthony@codemonkey.ws>
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Subject: Re: [Qemu-devel] [PATCH v2 0/7] APIC/IOAPIC cleanup
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To: Avi Kivity <avi@redhat.com>
Cc: Blue Swirl <blauwirbel@gmail.com>, "Liu >> \"Liu,
	Jinsong\"" <jinsong.liu@intel.com>, qemu-devel <qemu-devel@nongnu.org>, Markus Armbruster <armbru@redhat.com>, Paul Brook <paul@codesourcery.com>

On 08/23/2010 09:32 AM, Avi Kivity wrote:
>> Is bad?  The answer would depend on whether OtherState implemented 
>> methods or not.  If OtherState has no methods, it's fine.  If it has 
>> methods, it's bad.
>
>
> I don't see why.  As long as you can manipulate all of MyDevice's 
> state via MyDeviceState methods, why do you care about OtherState at all?

See below.

>>
>> Devices can contain references to structs and objects.  If a Device 
>> contains a reference to an object, the object should be stored in a 
>> BusState which is a container of Devices.  Therefore, the object 
>> should inherit from Device.
>
> I disagree.  It's up to the author to decide whether to split a Device 
> into 1 or 15 objects.
>
> If one of the other objects is also a subclass of DeviceState, then 
> you're probably violating that DeviceState's contract.  But that's a 
> different (and trivial) matter.
>
> (side point: in C no objects have constructors and methods.  in C++ 
> all objects have constructors and methods, even PODs)

Things that inherit from DeviceState have ctors/dtors.  Things that 
don't end up inventing their own and probably will do so poorly.

When implementing a C object model, you really need to have a base 
object that everything inherits from.  In glib, it's GObject.

Regards,

Anthony Liguori