Fix linking libvtkWrapping with Python wrapping and kits enabled on Mac

On Mac, the libvtkWrapping-8.1.1 library fails to link to libpython when configuring with VTK_WRAP_PYTHON and VTK_ENABLE_KITS enabled.

This commit ensures that the library links to libpython.

This fixes the following error:

FAILED: lib/libvtkWrapping-8.1.1.dylib
Undefined symbols for architecture x86_64:
  "_PyCallable_Check", referenced from:
      vtkPythonAlgorithm::SetPythonObject(_object*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillInputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillOutputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
  "_PyErr_Clear", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PyErr_Fetch", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PyImport_ImportModule", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PyInt_AsLong", referenced from:
      vtkPythonAlgorithm::CheckResult(char const*, vtkSmartPyObject const&) in vtkPythonAlgorithm.cxx.o
  "_PyInt_FromLong", referenced from:
      vtkPythonAlgorithm::FillInputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillOutputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
  "_PyObject_Call", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::SetPythonObject(_object*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillInputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillOutputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
  "_PyObject_GetAttrString", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::SetPythonObject(_object*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillInputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillOutputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
  "_PyObject_Str", referenced from:
      vtkPythonAlgorithm::PrintSelf(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, vtkIndent) in vtkPythonAlgorithm.cxx.o
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PySequence_Fast", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PySequence_Size", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PyString_AsString", referenced from:
      vtkPythonAlgorithm::PrintSelf(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, vtkIndent) in vtkPythonAlgorithm.cxx.o
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
  "_PyTuple_New", referenced from:
      GetPythonErrorString() in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::SetPythonObject(_object*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::ProcessRequest(vtkInformation*, vtkInformationVector**, vtkInformationVector*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillInputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o
      vtkPythonAlgorithm::FillOutputPortInformation(int, vtkInformation*) in vtkPythonAlgorithm.cxx.o

Do: test

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Branch-at: fcba8a82

added 42 commits

• fcba8a82...94ba4ab1 - 41 commits from branch vtk:master
• 65502d52 - Fix linking libvtkWrapping with Python wrapping and kits enabled on Mac

Compare with previous version

Do: test

This merge request has been queued for testing. Test results may be viewed on CDash or Buildbot (only visible from inside Kitware).

Branch-at: 65502d52

This is related to the changes from !1713 (merged).

+1 This looks good to me, and was necessary in order for me to build kits on OS X without link errors.

@brad.king do you see any potential issues with this change?

@iMichka please take a look.

Linking to python should not be required. I suspect a change like this one need to be done: d0aed867

In other word, since at run time, python symbols can be exported by either the python library or the python executable, we should not have to explicitly link the python library.

Hi. I'm on holidays without my computer, so I won't be able to review this now. I'll be back around the 2 August, so you may either wait for me or just merge it, and I'll do a post-merge review :)

I think @jcfr's suggestion is likely the best path forward. At runtime the symbols will be available. We just need to drop --no-undefined to avoid the complaint at link time.

This issue is specifically for MacOS/clang so --no-undefined doesn't apply, does it? The build never used --no-undefined or any equivalent.

On MacOSX, flag like -undefined dynamic_lookup should be used and this is the role of vtk_target_link_libraries_with_dynamic_lookup.

It looks like (1) something prevent the test _vtkCheckUndefinedSymbolsAllowed from working as expected on MacOSx or (2) vtk_target_link_libraries_with_dynamic_lookup is not used in some location.

Either way, now I am done adding support for Linux and Windows python wheels to https://github.com/jcfr/VTKPythonPackage, I will work on MAcOSX and I will tackle this.

I have another attempt at this which I will push shortly.

added 56 commits

• 65502d52...f3c3f8d4 - 55 commits from branch vtk:master
• de1a9397 - Fix linking libvtkWrapping with Python wrapping and kits enabled on Mac

Compare with previous version

Do: test

This merge request has been queued for testing. Test results may be viewed on CDash or Buildbot (only visible from inside Kitware).

Branch-at: de1a9397

The new code looks a little kludgy but it works for me.

@dgobbi Agreed.

Ideally should have a way to teach the linker to allow dynamic lookup of only a subset of symbols (python symbols in that case). That way, the linking would file if symbols different from the python ones are missing.

In the mean time

Cc: @thewtex