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Date: Fri, 16 Dec 2011 14:52:56 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH v3 00/20] qom: dynamic properties and
	composition tree
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To: Anthony Liguori <aliguori@us.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>, Peter Maydell <peter.maydell@linaro.org>, Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>, Jan Kiszka <jan.kiszka@siemens.com>, qemu-devel@nongnu.org, Luiz Capitulino <lcapitulino@redhat.com>, Markus Armbruster <armbru@redhat.com>

On 12/16/2011 02:51 PM, Anthony Liguori wrote:
> struct ISASerial {
>     Device parent;
>
>     UART _child uart;
>     ISABus _link *bus;
> };
>
> A child should be able to be part of the parent devices memory with its
> life cycle bound to the parents life cycle.  This is why a child
> property shouldn't be nullable.

100% agreed in principle.

But technically, if you do not make them pointers how do you handle 
children that, for some reason (broken reference counting for example) 
outlive the parent?  Aborting could be a very good answer. :)

Paolo