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

["Andreas Färber" <afaerber@suse.de>]

Am 31.05.2012 10:30, schrieb Markus Armbruster:
> Igor Mitsyanko <i.mitsyanko@samsung.com> writes:
> 
>> On 05/30/2012 08:19 PM, Igor Mammedov wrote:
>>> without assert it will crash at following point:
>>>     OBJECT_CHECK(type, obj, name) \
>>>      ((type *)object_dynamic_cast_assert(OBJECT(obj), (name)))
>>>        =>   object_dynamic_cast(obj, typename)
>>>          =>   object_is_type(obj, target_type)
>>>            =>   type_is_ancestor(obj->class->type, target_type);
>>>                                   ^^^
>>> so abort earlier and print nice message instead of SIGSEGV
>>>
>>> Signed-off-by: Igor Mammedov<imammedo@redhat.com>
>>> ---
>>>   qom/object.c |    2 ++
>>>   1 files changed, 2 insertions(+), 0 deletions(-)
>>>
>>> diff --git a/qom/object.c b/qom/object.c
>>> index 00bb3b0..444e2fc 100644
>>> --- a/qom/object.c
>>> +++ b/qom/object.c
>>> @@ -481,6 +481,8 @@ Object *object_dynamic_cast_assert(Object *obj, const char *typename)
>>>   {
>>>       Object *inst;
>>>
>>> +    g_assert(obj != NULL);
>>> +
>>>       inst = object_dynamic_cast(obj, typename);
>>>
>>>       if (!inst) {
>> 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.

Paolo, today OBJECT(p) is a pure C cast. I wonder if that was due to
TYPE_OBJECT being NULL at the time. Should we reconsider that on
qom-next with your patches to turn TYPE_OBJECT into a regular type?

Andreas

-- 
SUSE LINUX Products GmbH, Maxfeldstr. 5, 90409 Nürnberg, Germany
GF: Jeff Hawn, Jennifer Guild, Felix Imendörffer; HRB 16746 AG Nürnberg