foo.cc:88:5: error: ISO C++ forbids declaration of ‘output’ with no type [-fpermissive]
   88 |     output()
      |     ^~~~~~
foo.cc: In member function ‘int Person::output()’:
foo.cc:94:5: warning: no return statement in function returning non-void [-Wreturn-type]
   94 |     }
      |     ^