[Insight-developers] Why does ObjectFactoryBase::CreateInstance call o->Register() for objects it creates?

[Williams, Norman K]

There are only a few instances where ObjectFactoryBase::CreateInstance is
called to create an object, and they all immediately call UnRegister to
undo the Register in CreateInstance.


Sounds like a weirdness that needs to go away.

On 8/9/11 4:48 PM, "Bradley Lowekamp" <blowekamp at mail.nih.gov> wrote:

>Kent,
>
>The same methodology is used in the itkNewMacro, which is used in all
>news:
>
>define itkSimpleNewMacro(x)                                   \
>  static Pointer New(void)                                     \
>    {                                                          \
>    Pointer smartPtr = ::itk::ObjectFactory< x >::Create();    \
>    if ( smartPtr.GetPointer() == NULL )                       \
>      {                                                        \
>      smartPtr = new x;                                        \
>      }                                                        \
>    smartPtr->UnRegister();                                    \
>    return smartPtr;                                           \
>    }
>
>
>I also wonder why this is needed. I myself would have just returned with
>the following:
>
> if ( newobject )
>      {
>      return LightObject::Pointer(newobject );
>      }
>
>But there  is likely a case where the current implementation is needed,
>or perhaps it's just legacy from some ancient compiler.
>
>Brad
>
>On Aug 9, 2011, at 2:32 PM, Williams, Norman K wrote:
>
>> OK here's a simple question: Why does ObjectFactoryBase::CreateInstance
>> call newobject->Register()?
>>
>> ALL of the remaining leaks reported by valgrind in the new FEM framework
>> happen because CreateInstance returns an object with a reference count
>>of
>> 2.
>>
>> Corrolary question: ObjectFactoryBase is only used a few places:
>> TransformIOBase, SpatialObjectDuplicator and the FEM Framework. In the
>> first 2 places, LightObject::Unregister() is called to correct this
>> problem.
>>
>> Is there any rational reason CreateInstance should call Register() on
>>the
>> objects it returns?
>>
>>
>>
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