sg_location ();
sg_location(const std::string& path, int line = -1, int column = -1);
explicit sg_location(const char* path, int line = -1, int column = -1);
sg_location ();
sg_location(const std::string& path, int line = -1, int column = -1);
explicit sg_location(const char* path, int line = -1, int column = -1);