[Insight-developers] CMake questions related to SimpleITK C# wrapping

[Dan Mueller]

Hi Bradley,

Thanks for your response. See inline below.

On 18 June 2011 21:11, Bradley Lowekamp <blowekamp at mail.nih.gov> wrote:
> Hello Dan,
> Thanks for looking into the C# with simpleITK. SimpleITK should be a
> exciting and simple way to use ITK when easy of use and rapid prototyping
> are important along with  the many other benefits is has.
> On Jun 18, 2011, at 1:17 AM, Dan Mueller wrote:
>
> Hi Insight Developers,
>
> I have found some time here and there to fix/improve SimpleITK C#
> wrapping -- I can now generate SimpleITK C# wrappers on Windows using
> .NET or Mono, and on Linux using Mono.
>
> Great!
> I think one of the biggest things we are missing for C# is the nightly
> testing. It looks like I should look into the Mono thing some.
> It the build process fully automated with your patch? For some reason I
> thought there was a step or two that needed to be done by hand?

Yes, I have fixed the dependency issue, so the build is now fully automated.

> However, I still have a number of minor issues for which I need some advice:
>
> 1. LIBRARY_OUTPUT_DIRECTORY in Visual Studio:
> At CMake configure/generate time, I add a custom command (via the
> swig_add_module macro):
>    swig_add_module(SimpleITKCSharpNative csharp SimpleITK.i)
> For various reasons I need to force the output directory:
>    set_target_properties(SimpleITKCSharpNative PROPERTIES
> LIBRARY_OUTPUT_DIRECTORY ${CSHARP_BINARY_DIRECTORY})
> where CSHARP_BINARY_DIRECTORY =  /SimpleITK/Build/Wrapping/CSharpBinaries
>
> Under Linux the C# binary is nicely created in:
>    /SimpleITK/Build/Wrapping/CSharpBinaries
> However, under Windows (using Visual Studio 10 generator) the binary
> is created in:
>    /SimpleITK/Build/Wrapping/CSharpBinaries/Release
> (notice the configuration name "Release" at the end).
>
> Why is $(Configuration) added to the library output path? Can I prevent
> this?
> (This is not a big deal, but it requires yet another "if (WIN32)"
> check in the CMakeLists.txt which I'd prefer to avoid...)
>
>
>
> 2. Determining the platform in Linux:
> On Windows using Visual Studio generator, there is a VS macro
> $(PlatformShortName) which allows me to detect the platform name (x86
> or x64), eg:
>   add_custom_command(
>    COMMENT "Compiling C# ${type} ${name}"
>    OUTPUT ${name}.${output}
>    COMMAND ${CSHARP_COMPILER}
>    ARGS /t:${type} /out:${name}.${output}
> /platform:$(PlatformShortName) ${refs} ${sources} # <<< Use platform
> here
>    WORKING_DIRECTORY ${CSHARP_BINARY_DIRECTORY}
>    DEPENDS "${sources_dep}"
>  )
>
> Is there an equivalent to $(PlatformShortName) in UNIX make files? How
> can I determine the platform at CMake configuration/generation time
> and/or compile time under Linux?
>
>
> This sounds like to you need a CMake Guru to help you here. I CC'd David
> Cole for hopes of a response.
>
> 3. PixelIDValueEnum is too complex for some parsers/compilers:
> sitkPixelIDValues.h defines the following enum:
>  enum PixelIDValueEnum {
>    sitkUnknown = -1,
>    sitkUInt8 = PixelIDToPixelIDValue< BasicPixelID<uint8_t>
>
> ::Result,   // Unsigned 8 bit integer
>
>    sitkInt8 = PixelIDToPixelIDValue< BasicPixelID<int8_t> >::Result,
>   // Signed 8 bit integer
>    sitkUInt16 = PixelIDToPixelIDValue< BasicPixelID<uint16_t>
>
> ::Result, // Unsigned 16 bit integer
>
>    ...
>  }
>
> I get a number of strange issues related to the (complex) nature of
> the templated code assigning the enum values.
>
> These issues are two fold:
> (a) the SWIG parser does not seem to be able to determine the integer
> enum value. Here is the invalid C# code it generates:
>  public enum PixelIDValueEnum {
>    sitkUnknown = -1,
>    sitkUInt8 = PixelIDToPixelIDValue<(BasicPixelID<(uint8_t)>)>::Result,
>    sitkInt8 = PixelIDToPixelIDValue<(BasicPixelID<(int8_t)>)>::Result,
>    ...
>  }
> SWIG should be generating code like this (and does so nicely for other
> simpler SimpleITK enums):
>  public enum PixelIDValueEnum {
>    sitkUnknown = -1,
>    sitkUInt8 = 1,
>    sitkInt8 = 2,
>    ...
>  }
> Fortunately I can turn on "type safe enum" wrapping, which generates
> valid (but not so nice) C# code like this:
>  public sealed class PixelIDValueEnum {
>    public static readonly PixelIDValueEnum sitkUnknown = new
> PixelIDValueEnum("sitkUnknown", SimpleITKPINVOKE.sitkUnknown_get());
>    public static readonly PixelIDValueEnum sitkUInt8 = new
> PixelIDValueEnum("sitkUInt8", SimpleITKPINVOKE.sitkUInt8_get());
>    public static readonly PixelIDValueEnum sitkInt8 = new
> PixelIDValueEnum("sitkInt8", SimpleITKPINVOKE.sitkInt8_get());
>    ...
>  }
>
> I am glad the you have found a work around. While the C++ compiler can
> figure out the wacky meta-programmed PixelID value at compile time, it just
> too much for most other tools. Most of the target languages, just have some
> constant variables or similar structure to represent the PixelIDValueEnum.
> If the "type safe enum" is just too "not so nice", I suppose we could create
> an executable which prints the actual value of the enums. This output could
> then be fed into SWIG to make a more suitable interface.

I think type safe enums are fine for the moment. Just wanted to
mention it to see if other languages have s similar issue. (I forgot
to mention that Java has the same issue, but uses the type safe enums
by default so it worked out-of-the-box).

> (b) When compiling SimpleITK on Linux, I get lots of warnings stemming
> from PixelIDValueEnum:
> gcc version 4.5.2 (Ubuntu/Linaro 4.5.2-8ubuntu4)
>
>
> OK, most of that was just the instantiation structure of simpleITK's meta
> programming. I would recommend using an in editor compiler, where it
> highlights the error message and you can go directly to the cause of the
> error. Emacs easily does this.
> The following is the only actual warning is the block you sent:
>
> /home/dan/ITK/SimpleITK/Code/Common/sitkMemberFunctionFactory.txx:86:7:
> warning: case value ‘2’ not in enumerated type ‘itk::Image<signed
> char, 3u>::<anonymous enum>’
>
> This is rather unfortunate, and I it's most definitely a false positive. Do
> you know if there is a warning suppression for this particular message.
> It's caused by the usage of the following to define the ImageDimension
> member for the image classes, ( in ITK ):
> #define itkStaticConstMacro(name, type, value) enum { name = value }
> ( it would be nice is we could just use the static constant feature of
> C++0x, which has been a compiler extension for a while on many platforms )
> And the following code in SimpleITK:
>  switch( TImageType::ImageDimension )
>       {
>       case 3:
>         Superclass::m_PFunction3[ pixelID ] = Superclass::BindObject( pfunc,
> m_ObjectPointer );
>         break;
>       case 2:
>         Superclass::m_PFunction2[ pixelID ] = Superclass::BindObject( pfunc,
> m_ObjectPointer );
>         break;
>       default:
>         break;
>       }
> Perhaps the following should quiet it:
>  switch( int(TImageType::ImageDimension) )
>       {
> Additionally, there has just been a long topic to fix many warning just
> pushed to master. We are working on it. However, this particular one is new
> to me.
>
>
> I'm not sure anything can be done to help SWIG or gcc with the
> PixelIDValueEnum complexities, but I thought I should mention it...
>
> 4. Process for contributing changes:
> I guess this is a question for the SimpleITK people...
> What is the process to contribute these changes? I have cloned the
> SimpleITK.git repository and have made the changes against this. Do I
> simply push them to gerrit for review?
>
> Which repo have you clone? We recently moved the main one from git hub to
> kitware, but git hub is still a mirror.
> Basic info about the repository can be found here:
> http://www.itk.org/Wiki/ITK_Release_4/SimpleITK
> You should be able to use either gerrit, github, or as a last resort an
> e-mail patch to contribute.
> It depends on what you are most comfortable with. SimpleITK is currently a
> small development team, so we have not had the opportunity to develop
> detailed documentation for these procedures.

I cloned http://itk.org/SimpleITK.git.

I will submit my changes to gerrit in the coming days.

>
> 5. SimpleITK stability:
> At the moment there is only one C# example.
> How stable is SimpleITK? Is it stable enough that I can spend some
> time writing more C# examples? Or will things change?
>
> We are planning on taking an alpha tomorrow. I don't expect there to be wild
> changes in much of the API, just tweaks and what not. Along with expanding
> to new features.
> Writing new Examples woulds very much be appreciated. It is also important
> that they get executed as test to ensure they remain up to date.
> Additionally, it would help to ensure the stability of the C# interface.
> Please let us know how your experience is using the SImpleITK interface, and
> you are welcome to join the TCON to provide feedback, which is held on
> wednesdays at 9:30am EST.

This sounds pretty stable -- I will write more examples. I will also
make sure I enable them for testing.