[vtk-developers] const in set vector macros

[Will Schroeder]

There is a large, potential impact on our customers. We are already too
cavalier about changing API and we've pissed off a lot of folks. I can see
putting this down for a change in a major release at some point.
W

2008/11/7 David Cole <david.cole at kitware.com>

> I sort of agree with Karthik... It would be better if we could make VTK as
> a whole honor const where it makes sense. This, however, does not seem like
> a lightweight task by any means.
> However, I also think we should make it easy for people not to have to
> resort to const_cast madness.
>
> Changing vtkSetGet.h is a good start, but there are many method overrides
> in subclasses that will now have a different signature than their parent
> class methods unless they are carefully sought out and changed to match the
> new parent signature. You do not want to unintentionally change a method
> override to a method overload.
>
> After thinking about this for a little while, I'd be very hesitant to make
> this change without reserving a lot of time for chasing down strange
> behavior to follow...
>
>
> David
>
>
> On Fri, Nov 7, 2008 at 1:02 PM, Karthik Krishnan <
> karthik.krishnan at kitware.com> wrote:
>
>> VTK's public API as a whole does not respect constness. It might be
>> more painful if we were to make bits and pieces of the public API
>> const correct. Sometimes slightly correct is not better than
>> fully incorrect.
>>
>> Did you also check if you would be causing the wrappers
>> problems ?
>>
>> Thanks
>> --
>> karthik
>>
>> 2008/11/7 Burlen Loring <burlen.loring at kitware.com>:
>> > Hi,
>> >
>> > would anyone object to changing the vtkSetVectorXMacro's to respect
>> const
>> > pointers?
>> > for eg. the change to SetVector3Macro would be:
>> >
>> > -virtual void Set##name (type _arg[3]) \
>> > +virtual void Set##name (const type _arg[3]) \
>> >  { \
>> >  this->Set##name (_arg[0], _arg[1], _arg[2]);\
>> >  }
>> >
>> >
>> > This would be helpful in a situation like:
>> >
>> > class A
>> > {
>> > public:
>> >   const double *GetBlah(){ return this->Blah; }
>> > private:
>> >   double Blah[3];
>> > };
>> >
>> > class B : public vtkObject
>> > {
>> > public:
>> >   vtkSetVector3Macro(Bleh,double);
>> > private:
>> >   double Bleh[3];
>> > };
>> >
>> > A a;
>> > B *b=B::New();
>> > b->SetBleh(a.GetBlah());
>> >
>> > where I want to return a pointer to an array for efficiency but want to
>> > document, and enforce, that the array's contents aren't to be modified,
>> and
>> > don't want to end up using const_cast's everywhere I need to pass the
>> array
>> > to a vtkObject.
>> >
>> > --
>> > Burlen Loring
>> > Kitware, Inc.
>> > R&D Engineer
>> > 28 Corporate Drive
>> > Clifton Park, NY 12065-8662
>> > Phone: 518-371-3971 x137
>> >
>> >
>> > _______________________________________________
>> > vtk-developers mailing list
>> > vtk-developers at vtk.org
>> > http://www.vtk.org/mailman/listinfo/vtk-developers
>> >
>> >
>>
>>
>>
>> --
>> Karthik Krishnan
>> R&D Engineer,
>> Kitware Inc.
>> Ph: 518 371 3971 x119
>> Fax: 518 371 3971
>> _______________________________________________
>> vtk-developers mailing list
>> vtk-developers at vtk.org
>> http://www.vtk.org/mailman/listinfo/vtk-developers
>>
>
>
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>


-- 
William J. Schroeder, PhD
Kitware, Inc.
28 Corporate Drive
Clifton Park, NY 12065
will.schroeder at kitware.com
http://www.kitware.com
518-371-3971 (phone and fax)
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