Re: [Qemu-devel] [PATCH 1/3] qom-qobject: introduce object_property_{g, s}et_ptr

[Paolo Bonzini <pbonzini@redhat.com>]

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On 24/02/2017 17:54, Eric Blake wrote:
>> If you're setting UserDefOne from UserDefOneMore, some of the values are
>> going to be lost.  Presumably there was a reason why you used
>> UserDefOneMore, and therefore an error is the safe bet.
>>
>> If you're getting UserDefOne from UserDefOneMore, some of the values are
>> going to be lost.  However, it's reasonable that you didn't even know
>> that UserDefOneMore existed, which makes it sensible to allow reading
>> into a covariant type.
>
> How often to we add qapi subtypes, but not adjust the rest of the code
> base to cope with it existing?  Is it going to be less of a maintenance
> burden just patching all the uses of the property getters to deal with
> the new type than it is to keep the non-strict visitor?

It's not about adjusting the rest the code, it's about the other code
not caring about the data in the subtype.  Why should it be using it
rather than the supertype?

Paolo


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