Compilare: user.cpp: In function ‘std::ifstream& operator>>(std::ifstream&, PTX&)’: user.cpp:18:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^ user.cpp: In function ‘std::ofstream& operator<<(std::ofstream&, PTX&)’: user.cpp:21:5: warning: no return statement in function returning non-void [-Wreturn-type] } ^