Just got stuck in compiling a simple C++ program with Eigen C++ when using intel oneAPI DPC++/C++ compiler: The example contains two .cpp files (main.cpp and Preprocessing.cpp) and one include file (struct_INFO.h).

I don't know why the compiler gives errors as the image shows. Error messages from Intel compiler:

duplicate symbol: bool const std::_Is_integral<bool>
duplicate symbol: bool const std::_Is_integral<char>
duplicate symbol: bool const std::_Is_integral<signed char> 
duplicate symbol: bool const std::_Is_integral<unsigned char>
duplicate symbol: bool const std::_Is_integral<wchar_t>
duplicate symbol: bool const std::_Is_integral<char16_t>
duplicate symbol: bool const std::_Is_integral<char32_t>

... All the errors are similar, so I just show some of them.

It seems that I can include neither the Eigen head file (<Eigen/Core>) nor the head file struct_INFO.h, which containing Eigen head file, in my subroutine Preprocessing.cpp.

The only way that I know to fix the problem is to merge the two .cpp files into one.

However, this approach is kind of cumbersome that I need to put all the subroutines in one file as long as I need to use the Eigen variables.

Does anyone know how to solve this problem? Thank you.

1. main.cpp:

   #include "struct_INFO.h"
   #include <Eigen/Core>
   
   int Preprocessing(struct_INFO& struct_INFO_obj);
   
   int main(int* argc, char** argv)
   {
       struct_INFO struct_INFO_obj;
       Preprocessing(struct_INFO_obj);
       return 0;
   }
   

2. Preprocessing.cpp

   #include "struct_INFO.h"
   
   int Preprocessing(struct_INFO& struct_INFO_obj)
   {
          return 1;
   }
   

3. struct_INFO.h

   #include <Eigen/Core>
   
   class struct_INFO
   {
          public:
          Eigen::Matrix<float, Eigen::Dynamic, Eigen::Dynamic> Matrix;
   };