System eigen

[dzenanz]

A project which builds against ITK with system Eigen fails with c:\misc\bluequartz\sdk-rwdi\itk-src\modules\core\common\include\itkSymmetricEigenAnalysis.h(22): fatal error C1083: Cannot open include file: 'itk_eigen.h': No such file or directory (compiling source file C:\Misc\BlueQuartz\DREAM3D_Plugins\ITKImageProcessing\ITKImageProcessingFilters\ITKImageReader.cpp). The ITK is also built without default modules.

[phcerdan]

Thanks @dzenanz. Is that a clean build after eigen3 was introduced? The folder with itk_eigen.h should be included using system eigen3. If still failing I will have a look first thing in a couple of days.

[skn123]

Please reopen this
CMake Error at CMake/ITKModuleMacros.cmake:468 (add_library):
Target "ITKCommon" links to target "Eigen3::Eigen" but the target was not
found. Perhaps a find_package() call is missing for an IMPORTED target, or
an ALIAS target is missing?
Call Stack (most recent call first):
Modules/Core/Common/src/CMakeLists.txt:179 (itk_module_add_library)

[skn123]

[100%] Linking CXX executable ../../../../bin/itkTestDriver
/usr/bin/ld: cannot find -lEigen3::Eigen
clang: error: linker command failed with exit code 1 (use -v to see invocation)
Modules/Core/TestKernel/src/CMakeFiles/itkTestDriver.dir/build.make:153: recipe for target 'bin/itkTestDriver' failed
make[2]: *** [bin/itkTestDriver] Error 1
CMakeFiles/Makefile2:15640: recipe for target 'Modules/Core/TestKernel/src/CMakeFiles/itkTestDriver.dir/all' failed
make[1]: *** [Modules/Core/TestKernel/src/CMakeFiles/itkTestDriver.dir/all] Error 2
Makefile:151: recipe for target 'all' failed
make: *** [all] Error 2

Setting this line solved the issue:

if(ITK_USE_SYSTEM_EIGEN)
set(_eigen_itk_target) <-------
else()
set(_eigen_itk_target ITKInternalEigen3::Eigen)
endif()

Remove that Eigen3::Eigen

[phcerdan]

There is a find_package(Eigen3) in that file in the case of ITK_USE_SYSTEM_EIGEN. Not sure why is not called by other internal modules...

Your problem can be solved adding an extra file: itk-module-init.cmake in the module:

if(ITK_USE_SYSTEM_EIGEN)
  find_package(Eigen3 REQUIRED CONFIG)
endif()

I am going to update Eigen to the latest release (3.7) and check if they have solved the annoying gcc shadowed warnings. If that's the case, we could re-think on changing ITKCommon to only depends on ITKEigen3 at compile time, instead of publicly.