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Date: Fri, 16 Dec 2011 17:17:09 +0100
From: Paolo Bonzini <pbonzini@redhat.com>
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Subject: Re: [Qemu-devel] [PATCH 1/8] qapi: fix NULL pointer dereference
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To: Anthony Liguori <anthony@codemonkey.ws>
Cc: kwolf@redhat.com, qemu-devel@nongnu.org

On 12/16/2011 04:54 PM, Anthony Liguori wrote:
> On 12/16/2011 09:42 AM, Paolo Bonzini wrote:
>> On 12/16/2011 04:23 PM, Anthony Liguori wrote:
>>> Ok. I think nullable strings are not a good idea simply because it
>>> means that a property can have a state that cannot be set.
>>
>> How is this different from NULL links? (Honest, not trick question :)).
>
> An empty string == NULL for links.
>
> If a pointer is NULL, an empty string is returned. So get/set is full
> symmetric.

Ok, so we can do the same for "pointer" properties.  I'm just a bit 
worried about serial numbers, where "-device virtio-blk-pci,...,serial=" 
is different from no serial at all.  One shows "" in info qtree, the 
other shows <null>.

> For JSON, but it doesn't map to a config file easily nor does it map to
> command line syntax well.

You can force nullable properties to have a null default (which is now 
the case in qdev), but I agree that's not too nice.

Paolo