platform_specific.cpp

mylib.h

#ifndef MYLIB_H
#define MYLIB_H

std::string get_operating_system_name();

#endif // MYLIB_H



mylib.cpp

#include "mylib.h"

#ifdef __APPLE__
#include "os_x_mylib.cpp"
#elif defined __linux__
#include "linux_mylib.cpp"
#endif

.. any other platform independent code ..



os_x_mylib.cpp
std::string get_operating_system_name() {
  return "os x";
}

linux_mylib.cpp

std::string get_operating_system_name() {
  return "linux";
}