[vtk-developers] Smart pointer declaration macro?
Wes Turner
wes.turner at kitware.com
Thu Jan 28 09:24:11 EST 2010
I'm not really against the idea, but I am not convinced that this actually
does anything real for us. We are just replacing the line:
vtkSmartPointer<vtkClass> myLocal = vtkSmartPointer<vtkClass>::New();
with
vtkSmartPointer<vtkClass> myLocal(true);
I don't mind change and will go along with whatever is decided, but we are
trading conciseness for clarity. I generally don't mind multiple line code,
so shortening the signature is not a big deal to me. Is there really
consensus that this is needed?
- Wes
On Thu, Jan 28, 2010 at 9:05 AM, David Doria
<daviddoria+vtk at gmail.com<daviddoria%2Bvtk at gmail.com>
> wrote:
> On Thu, Jan 28, 2010 at 9:01 AM, Will Schroeder
> <will.schroeder at kitware.com> wrote:
> > This has been part of the VTK naming convention as well, at least in
> > practice.
> >
> > On Thu, Jan 28, 2010 at 8:54 AM, Karthik Krishnan
> > <karthik.krishnan at kitware.com> wrote:
> >>
> >> Abbreviations in ITK are in the "things to avoid list" as far as
> >> naming conventions go, unless the abbreviation is a standard one used
> >> in the field such as FFT ..
> >>
> >> I suppose this is part of the VTK coding convention as well ? If not
> >> it should probably be in there
> >>
> >> On Thu, Jan 28, 2010 at 8:50 AM, Will Schroeder
> >> <will.schroeder at kitware.com> wrote:
> >> > Sorry, I don't like the abbreviation, I love change :-)
> >> >
> >> >
> >> > On Thu, Jan 28, 2010 at 8:45 AM, Jeff Baumes <jeff.baumes at kitware.com
> >
> >> > wrote:
> >> >>
> >> >> On Wed, Jan 27, 2010 at 10:58 AM, Will Schroeder
> >> >> <will.schroeder at kitware.com> wrote:
> >> >> > VTK has a verbose, self documenting style (for better or worse).
> I'd
> >> >> > like to
> >> >> > stick with it if possible.
> >> >>
> >> >> Will,
> >> >>
> >> >> Are you suggesting no change? Or just that you don't like the
> >> >> abbreviated typedefs like vtkRendererSP?
> >> >>
> >> >> Jeff
> >> >>
> >> >> >
> >> >> >
> >> >> > On Wed, Jan 27, 2010 at 10:56 AM, David Cole <
> david.cole at kitware.com>
> >> >> > wrote:
> >> >> >>
> >> >> >> On Wed, Jan 27, 2010 at 8:35 AM, Jeff Baumes
> >> >> >> <jeff.baumes at kitware.com>
> >> >> >> wrote:
> >> >> >>>
> >> >> >>> On Tue, Jan 26, 2010 at 12:44 PM, Marcus D. Hanwell
> >> >> >>> <marcus.hanwell at kitware.com> wrote:
> >> >> >>> > On Friday 08 January 2010 16:46:47 David Cole wrote:
> >> >> >>> >> On Fri, Jan 8, 2010 at 4:08 PM, Marcus D. Hanwell <
> >> >> >>> >>
> >> >> >>> >> marcus.hanwell at kitware.com> wrote:
> >> >> >>> >> > I would like to add my -1, I think needing to split lines in
> >> >> >>> >> > order
> >> >> >>> >> > to
> >> >> >>> >> > declare
> >> >> >>> >> > a new local variable is a little much. I came from a C++
> >> >> >>> >> > background
> >> >> >>> >> > where
> >> >> >>> >> > any
> >> >> >>> >> > object could be declared on the stack though. For things
> like
> >> >> >>> >> > the
> >> >> >>> >> > examples it
> >> >> >>> >> > seems to hurt readability to me.
> >> >> >>> >> >
> >> >> >>> >> > Pointer:
> >> >> >>> >> > vtkFloatArray *myTable = vtkFloatArray::New();
> >> >> >>> >> > myTable->Delete();
> >> >> >>> >> > myTable = NULL;
> >> >> >>> >> >
> >> >> >>> >> > Smart pointer:
> >> >> >>> >> > vtkSmartPointer<vtkFloatArray> myTable =
> >> >> >>> >> > vtkSmartPointer<vtkFloatArray>::New();
> >> >> >>> >> >
> >> >> >>> >> > Smart pointer with macro:
> >> >> >>> >> > VTK_CREATE(vtkFloatArray, myTable);
> >> >> >>> >> >
> >> >> >>> >> > Stack:
> >> >> >>> >> > vtkFloatArray myTable;
> >> >> >>> >> >
> >> >> >>> >> > I would prefer to be able to use something like the first or
> >> >> >>> >> > the
> >> >> >>> >> > last. In
> >> >> >>> >> > classes etc it is often a different story. It seems like
> there
> >> >> >>> >> > should be
> >> >> >>> >> > some
> >> >> >>> >> > macro or template function to generate variables with less
> >> >> >>> >> > repetition.
> >> >> >>> >>
> >> >> >>> >> Prefer the first and last as much as you want, but we simply
> >> >> >>> >> can't
> >> >> >>> >> use
> >> >> >>> >> them
> >> >> >>> >> in VTK. The first leads to memory leaks because people forget
> >> >> >>> >> the
> >> >> >>> >> Delete
> >> >> >>> >> calls. The last cannot be done with vtkObject derived classes
> >> >> >>> >> because
> >> >> >>> >> of
> >> >> >>> >> the nature of vtkObject reference counting...
> >> >> >>> >>
> >> >> >>> > Wasn't suggesting either (just pointing out the shorter syntax
> >> >> >>> > that
> >> >> >>> > people
> >> >> >>> > miss), although the first is still widely used in VTK.
> >> >> >>> >
> >> >> >>> >> So we have to pick one of the middle ones...
> >> >> >>> >>
> >> >> >>> >> It's unfortunate that we've had two +1's and two -1's... that
> >> >> >>> >> leaves
> >> >> >>> >> us at
> >> >> >>> >> 0 for the moment. I guess that and the fact that it's Friday
> >> >> >>> >> makes
> >> >> >>> >> it
> >> >> >>> >> fairly easy to put off a decision until at least next week.
> ;-)
> >> >> >>> >>
> >> >> >>> >> *If* we do go with a macro-based approach, I think we can all
> >> >> >>> >> agree
> >> >> >>> >> there
> >> >> >>> >> should be one centralized macro that does this and it should
> be
> >> >> >>> >> used
> >> >> >>> >> *everywhere* that vtkSmartPointer::New is presently used.
> >> >> >>> >
> >> >> >>> > What about a vtkLocalPointer<vtkClass> myLocal; where the
> default
> >> >> >>> > constructor
> >> >> >>> > makes an instance on the VTK class? It would also be possible
> to
> >> >> >>> > have a
> >> >> >>> > constructor take an argument (may be a little clunkier) such as
> >> >> >>> > vtkSmartPointer<vtkClass> myLocal(true); if we do not want to
> >> >> >>> > introduce
> >> >> >>> > yet
> >> >> >>> > another class.
> >> >> >>> >
> >> >> >>> > Alternate options a and b...
> >> >> >>> >
> >> >> >>> > a) vtkLocalPointer<vtkClass> myLocal;
> >> >> >>> > b) vtkSmartPointer<vtkClass> myLocal(true);
> >> >> >>> >
> >> >> >>> > Would this be preferable to a macro? It seems like a better way
> >> >> >>> > to
> >> >> >>> > go
> >> >> >>> > to me,
> >> >> >>> > and in terms of API and conciseness seems to satisfy our
> >> >> >>> > requirements
> >> >> >>> > better
> >> >> >>> > than the current approach. It would still be possible to share
> >> >> >>> > the
> >> >> >>> > pointer
> >> >> >>> > too, due to the reference counting in vtkObject derived
> classes.
> >> >> >>>
> >> >> >>> I think option b is a good option. It seems that it would be odd
> to
> >> >> >>> have two different pointer classes, where the only difference is
> >> >> >>> what
> >> >> >>> they do on construction.
> >> >> >>>
> >> >> >>> The biggest grudge I have about the current option is that it
> >> >> >>> almost
> >> >> >>> always requires a split line if you constrain yourself to 80
> >> >> >>> characters. If your type name is more than about 15 characters
> >> >> >>> (which
> >> >> >>> many VTK types are), you have to split your line:
> >> >> >>>
> >> >> >>> vtkSmartPointer<type> name = vtkSmartPointer<type>::New();
> >> >> >>> 16 + t + 2 + n + 19 + t + 9 = 46 + 2*t + n
> >> >> >>>
> >> >> >>> Option b, even though not the most concise, would make it easy to
> >> >> >>> stay
> >> >> >>> within that limit, about halving the number of characters:
> >> >> >>>
> >> >> >>> vtkSmartPointer<type> name(true);
> >> >> >>> 16 + t + 2 + n + 7 = 25 + t + n
> >> >> >>>
> >> >> >>> Jeff
> >> >> >>
> >> >> >>
> >> >> >> Another solution worth considering is simply making a typedef
> called
> >> >> >> "vtkRendererSP" that is a typedef for
> "vtkSmartPointer<vtkRenderer>"
> >> >> >> --
> >> >> >> that
> >> >> >> would allow you to:
> >> >> >> vtkRendererSP renderer = vtkRendererSP::New();
> >> >> >> It gives you the shorter names you're all longing for, without
> >> >> >> changing
> >> >> >> anything else already in VTK...
> >> >> >>
> >> >> >> David C.
> >> >> >>
> >> >> >> _______________________________________________
> >> >> >> Powered by www.kitware.com
> >> >> >>
> >> >> >> Visit other Kitware open-source projects at
> >> >> >> http://www.kitware.com/opensource/opensource.html
> >> >> >>
> >> >> >> Follow this link to subscribe/unsubscribe:
> >> >> >> http://www.vtk.org/mailman/listinfo/vtk-developers
> >> >> >>
> >> >> >>
> >> >> >
> >> >> >
> >> >> >
> >> >> > --
> >> >> > William J. Schroeder, PhD
> >> >> > Kitware, Inc.
> >> >> > 28 Corporate Drive
> >> >> > Clifton Park, NY 12065
> >> >> > will.schroeder at kitware.com
> >> >> > http://www.kitware.com
> >> >> > (518) 881-4902
> >> >> >
> >> >>
> >> >>
> >> >>
> >> >> --
> >> >> Jeff Baumes, Ph.D.
> >> >> R&D Engineer, Kitware Inc.
> >> >> (518) 881-4932
> >> >> jeff.baumes at kitware.com
> >> >
> >> >
> >> >
> >> > --
> >> > William J. Schroeder, PhD
> >> > Kitware, Inc.
> >> > 28 Corporate Drive
> >> > Clifton Park, NY 12065
> >> > will.schroeder at kitware.com
> >> > http://www.kitware.com
> >> > (518) 881-4902
> >> >
> >> > _______________________________________________
> >> > Powered by www.kitware.com
> >> >
> >> > Visit other Kitware open-source projects at
> >> > http://www.kitware.com/opensource/opensource.html
> >> >
> >> > Follow this link to subscribe/unsubscribe:
> >> > http://www.vtk.org/mailman/listinfo/vtk-developers
> >> >
> >> >
> >> _______________________________________________
> >> Powered by www.kitware.com
> >>
> >> Visit other Kitware open-source projects at
> >> http://www.kitware.com/opensource/opensource.html
> >>
> >> Follow this link to subscribe/unsubscribe:
> >> http://www.vtk.org/mailman/listinfo/vtk-developers
> >>
> >
> >
> >
> > --
> > William J. Schroeder, PhD
> > Kitware, Inc.
> > 28 Corporate Drive
> > Clifton Park, NY 12065
> > will.schroeder at kitware.com
> > http://www.kitware.com
> > (518) 881-4902
>
> OK, so is everyone on board with Marcus' suggestion of:
>
> vtkSmartPointer<vtkClass> myLocal(true);
>
> If so, who is going to do it?
>
> Thanks,
>
> David
> _______________________________________________
> Powered by www.kitware.com
>
> Visit other Kitware open-source projects at
> http://www.kitware.com/opensource/opensource.html
>
> Follow this link to subscribe/unsubscribe:
> http://www.vtk.org/mailman/listinfo/vtk-developers
>
>
--
Wesley D. Turner, Ph.D.
Kitware, Inc.
Technical Leader
28 Corporate Drive
Clifton Park, NY 12065-8662
Phone: 518-881-4920
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