类引用作为函数返回值的问题

class Object{
public:
 static int r(){
    int i=1;
    return i;
  }
};

int main(int argc, char const *argv[]) {
  int& i=Object::r();
   return 0;
}

main.cpp:40:19: error: invalid initialization of non-const reference of type ‘int&’ from an rvalue of type ‘int’

class Object{
public:
    static Object&  new_instance(){
    //只能使用非引用的方式将局部对象变量传出去
    Object o;
    return o;
  }
  static int & f(){
    //这里也有上述问题
    int i=1;
    return i;
  }
}
int main(int argc, char const *argv[]) {
　　const int& i=Object::f();
 　 const Object & o=Object::new_instance();
　　printf("%d\n",i );
　　printf("%d\n",o.i);
}

main.cpp: In static member function ‘static Object& Object::new_instance()’:
main.cpp:17:12: warning: reference to local variable ‘o’ returned [-Wreturn-local-addr]
     Object o;
            ^
main.cpp: In static member function ‘static int& Object::f()’:
main.cpp:22:9: warning: reference to local variable ‘i’ returned [-Wreturn-local-addr]
     int i=1;