[Insight-developers] Fixed width integer types, itkIntTypes, and portable 64-bit integer

[Bill Lorensen]

Looks like a clean solution that is adaptable to the future.

On Mon, Dec 7, 2009 at 9:19 AM, Brad King <brad.king at kitware.com> wrote:
> Tom Vercauteren wrote:
>> From a purely aesthetic point of view, I have to say that
>> kwsys::FundamentalType_IntXX looks a little long.
>>
>> From a broader perspective, I also tend to like your third option
>> because cstdint will become standard c++ (it is in TR1).
> [snip]
> Sean McBride wrote:
>> My 2¢: I think using the stdint.h types is best.  After all, they are
>> the standardized solution to this very problem!  And they are easier to
>> type and read than something like kwsys::FundamentalType_IntXX.
>
> FYI, the actual names of the KWSys types in ITK would be of the form:
>
>  itksysFundamentalType_U?Int(8|16|32|64)
>
> However, these were not meant for direct use.  They are meant as
> try-compile results with out-of-the-way names that can be typedef'd
> as needed.
>
> The problem with <stdint.h> (or really <cstdint> for future C++) is that
> providing compatibility with compilers that do not provide it must be done
> carefully to avoid namespace violations.  I'm aware of several projects
> that just typedef int32_t in the global namespace of public headers :(
> We need a better solution.
>
> I suggest that we define the same types that stdint.h defines, except
> put them in the itk:: namespace.  We can use stdint.h where available
> and fall back on KWSys FundamentalType to get the types elsewhere:
>
> // Common/itkStdInt.h
> #ifdef ITK_HAVE_STDINT_H
> # include <stdint.h>
> namespace itk {
>  typedef ::int32_t int32_t; // OR using ::int32_t;
>  typedef ::int64_t int64_t;
>  ...
> }
> #else
> # include <itksys/FundamentalType.h>
> namespace itk {
>  typedef ::itksysFundamentalType_Int32 int32_t;
>  typedef ::itksysFundamentalType_Int64 int64_t;
>  ...
> }
> #endif
>
> This approach will work everywhere, avoids defining names outside the
> "itk::" namespace, and allows ITK code to use the types without any
> qualification.  When <cstdint> is standard in the future, we can switch
> the definitions to
>
> #include <cstdint>
> namespace itk {
>  using ::std::int32_t;
>  using ::std::int64_t;
>  ...
> }
>
> I think the same approach is already in use by the Boost community.
>
> -Brad K
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