[Insight-developers] Returning a smart pointer or a pointer?

[Bill Lorensen]

Maybe we should look at the demons registration. Perhaps it can use
the function more efficiently.

Bill

On Mon, May 19, 2008 at 1:22 PM, Tom Vercauteren
<tom.vercauteren at m4x.org> wrote:
> Hi all,
>
>> The change will affect users that create a subclass and override the method.
> This was indeed the backwards compatibility issue I was thinking of. I
> just cannot really figure why someone would do something like that...
> But as Bill said, this is unpredictable.
>
>
>>> a) When the object to be returned is a member variable of the
>>>   class, then a raw pointer is returned, and preferably a
>>>   "const" raw pointer.
>>>
>>>
>>> b) When the object to be returned is a newly created object,
>>>   then a SmartPointer is the preferred method, since it will
>>>   force users of this class to receive the value in a SmartPointer
>>>   and will prevent the returned object from "death in transit".
> Ok thanks for the clarification.
>
>> How much of a performance hit are you seeing?
>>
>> Maybe we will have to define a new method? Are their other classes
>> that have the same p[problem?
> I don' remember the exact performance hit. I was at least a few
> percents since it was appearing on the profiler output. I haven't seen
> any other problematic methods but haven't looked for it. I just check
> the one that was appearing on the profiler output.
>
>> What this function returns is a handle on an image. I fail to see the case
>> where you'd be dereferencing this smart pointer often enough to affect
>> program performance. If you are, you probably need to be using
>> itk::ImageRegionIterator, or hoist calls to access methods via smart
>> pointers outside of inner loops.
> I understand that, but I am not responsible for the code calling this
> method. It was somewhere in the demons registration hierarchy.
>
> Tom
>