Re: [Qemu-devel] [PATCH qom-next] qom: make object cast assert if NULL object is passed as argument

[Markus Armbruster]

Andreas Färber <address@hidden> writes:

> Am 31.05.2012 13:17, schrieb Igor Mammedov:
>> On 05/31/2012 12:16 PM, Paolo Bonzini wrote:
>>> Il 31/05/2012 10:30, Markus Armbruster ha scritto:
>>>>>> Makes much sense, but maybe it should be done in OBJECT() cast? Assert
>>>>>> when we do OBJECT(NULL).
>>>> In my opinion, OBJECT(p) where p is a null pointer is perfectly valid
>>>> and should yield a null pointer.
>>>
>>> Perhaps object_dynamic_cast and object_dynamic_cast_assert should do the
>>> same?
>>>
>> 
>> or better object_dynamic_cast should return NULL if obj is NULL,
>> after all it's expected that it may return NULL
>
> That's what I was suggesting: I think that we should define "NULL is not
> of type TYPE_FOO" and thus have the ..._is_... functions return false,
> and have the ..._cast_assert assert.

Is it?

Igor: object_dynamic_cast should return NULL if obj is NULL,

You: have the ..._cast_assert assert [on null argument, I presume]

Doesn't sound like the same suggestion to me :)

If I understood you correctly: what do such assertions buy us other than
silliness like

    p ? some_cast(p) : NULL

?

> So I still think this patch is correct. It could be accompanied by
> further patches adding error handling in the remaining functions.

I'm not convinced.