/in/foo.cc:4:1: error: ISO C++ forbids declaration of 'monthday' with no type [-fpermissive]
    4 | monthday(int m)
      | ^~~~~~~~
/in/foo.cc:14:1: error: ISO C++ forbids declaration of 'midmonthday' with no type [-fpermissive]
   14 | midmonthday(int m1, int m2)
      | ^~~~~~~~~~~