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

[Luis Ibanez]

Hi Tom,

In general:

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".


Looking at the itk::PDEDeformableRegistrationFunction, the
returned deformation field is actually hold by a member
variable of this class, therefore, it seems that it will be
safe to use method (a) [raw pointer].

Could you run an Experimental build with this change ?

and if goes well, then simply commit the change.

This shouldn't have any backward compatibility implications,
since any user currently receiving the variable will still
be able to receive it from a raw pointer.


   Luis


-----------------------
Tom Vercauteren wrote:
> Hi all,
> 
> Since I am not sure to fully understand ITK's policy regarding the use
> of smart pointers versus pointers, I would appreciate any feedback on
> the following question:
> Why does itk::PDEDeformableRegistrationFunction::GetDeformationField
> returns a smart pointer and not a pointer and can we change that?
> 
> 
> The reason I am asking is because I realized that returning a smart
> pointer was affecting the performance of my application. Changing the
> return type to a usual pointer led to a measurable speedup.
> 
> Since most other functions return a usual pointer it seems like
> itk::PDEDeformableRegistrationFunction::GetDeformationField should
> also return a pointer. If we change the return type, some users may
> run into backwards compatibility issues (e.g. a class inherits from
> PDEDeformableRegistrationFunction but redefines GetDeformationField).
> This seems unlikely though...
> 
> 
> Thanks,
> Tom
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