[Insight-developers] STYLE: Un-necessary use of static_cast -- should we care?

[Matt McCormick]

On Mon, Jul 23, 2012 at 9:22 PM, Williams, Norman K
<norman-k-williams at uiowa.edu> wrote:
> RE unnecessary casts: Personally, I think casts uglify code and should
> only be there as a way for the programmer to communicate intention to the
> compiler.
>
>
> RE adding dynamic casts: I don't know what the real overhead of a
> dynamic_cast vs a static_cast entails, and I suspect it varies depending
> on what compiler you use. Determining if it is logically impossible for
> dynamic_cast to fail isn't easy; and not all filters are written in such a
> way that prevent assigning bad inputs, like adding an Image where a Mesh
> is expected.
>
> I like Sean McBride's idea of a debug-only assert.  In fact it might be
> useful to use static_cast for release and dynamic_cast + assert(rval != 0)
> for debug builds.

Keep in mind that static_cast is done at compile time and dynamic_cast
is done during runtime.  My understanding is that dynamic_cast can be
"expensive", and an assert is not saving anything relative to the cost
of the dynamic_cast.

Some performance numbers:

  http://tinodidriksen.com/2010/04/14/cpp-dynamic-cast-performance/

Thanks,
Matt

>
> On 7/23/12 3:58 PM, "Matt McCormick" <matt.mccormick at kitware.com> wrote:
>
>>>
>>> So the question is this: do we keep static_cast where they aren't
>>>needed?
>>
>>Since it is a matter of human-readability, something consistent is
>>preferred, whatever that may be...
>>
>>> and should we add dynamic_cast in the frequent case where an input or
>>> output of a filter is assumed to be of a particular type?
>>>
>>
>>If it is not logically possible in the code for the dynamic_cast to
>>fail, and given the GetInput/GetOutput consequences, avoiding
>>unnecessary overhead seems best.
>
>
>
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