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

[Markus Armbruster]

Igor Mitsyanko <address@hidden> 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<address@hidden>
>> ---
>>   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.