[vtk-developers] Implicit copy constructors in VTK

[Robert Maynard]

Personally I don't see enough complaints about people forgetting to
follow the rule of three to add another macro helper to VTK.
We have a smoke test that does verify that all classes that derive
from vtkObject have private copy constructor and copy assignment
operator.


On Wed, Jul 24, 2013 at 11:55 AM, Jean-Christophe Fillion-Robin
<jchris.fillionr at kitware.com> wrote:
> Would it make sense to provide a VTK_DISABLE_COPY() macro ?  (Similar to
> what is done within Qt with Q_DISABLE_COPY [1])
>
> [1] http://qt-project.org/doc/qt-5.0/qtcore/qobject.html#Q_DISABLE_COPY
>
>
> On Wed, Jul 24, 2013 at 11:48 AM, Marcus D. Hanwell
> <marcus.hanwell at kitware.com> wrote:
>>
>> I agree with Rob, and can take care of putting a patch together for
>> the classes you call out. The rules outlined only make sense for
>> vtkObject derived classes, we should provide clear guidelines for
>> those that are not part of that hierarchy too.
>>
>> On Wed, Jul 24, 2013 at 11:06 AM, Robert Maynard
>> <robert.maynard at kitware.com> wrote:
>> > The VTK coding standards should be amended to state that those rules
>> > are only valid for classes that derive from vtkObject.
>> >
>> > Classes like vtkBond, vtkTuple, vtkBoundingBox all which don't inherit
>> > from vtkObject should follow the rule of three and implement the copy
>> > and assignment constructor if they implement a destructor.
>> >
>> > On Wed, Jul 24, 2013 at 10:50 AM, Sean McBride <sean at rogue-research.com>
>> > wrote:
>> >> Hi all,
>> >>
>> >> So I'm looking at the clang warnings on Rogue7, but need C++ help
>> >> before I can proceed further.  We have two similar warnings, repeated for
>> >> several classes:
>> >>
>> >> VTK/Common/DataModel/vtkBond.h:30:3: warning: definition of implicit
>> >> copy constructor for 'vtkBond' is deprecated because it has a user-declared
>> >> destructor [-Wdeprecated]
>> >>   ~vtkBond();
>> >>   ^
>> >>
>> >> VTK/Common/Math/vtkQuaternion.h:201:8: warning: definition of implicit
>> >> copy constructor for 'vtkQuaternion<float>' is deprecated because it has a
>> >> user-declared copy assignment operator [-Wdeprecated]
>> >>   void operator=(const vtkQuaternion<T>& q);
>> >>        ^
>> >>
>> >> From what I can tell, in C++11, the implicit generation of copy
>> >> constructors is now deprecated if 1) you provide a user-declared destructor
>> >> or 2) you provide a user-declared copy assignment operator.
>> >> <http://stackoverflow.com/a/11255258>
>> >>
>> >> So it would seem a solution is to provide an explicit copy constructor,
>> >> but VTK's coding standards gives me pause: "Classes should have protected
>> >> constructors and destructors, and privately declared but unimplemented copy
>> >> constructor and assignment operator. Rationale: VTK’s reference counting
>> >> implementation depends on carefully controlling each object’s reference
>> >> count".
>> >>
>> >> So now I'm not sure how to proceed...
>> >>
>> >> Thanks,
>> >>
>> >> --
>> >> ____________________________________________________________
>> >> Sean McBride, B. Eng                 sean at rogue-research.com
>> >> Rogue Research                        www.rogue-research.com
>> >> Mac Software Developer              Montréal, Québec, Canada
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