/in/foo.cc:55:7: error: declaration of 'operator void' as non-function
  void sort()
       ^~~~
/in/foo.cc:55:2: error: expected ';' at end of member declaration
  void sort()
  ^~~~
/in/foo.cc:55:12: error: ISO C++ forbids declaration of 'sort' with no type [-fpermissive]
  void sort()
            ^
/in/foo.cc:55:12: error: expected ';' at end of member declaration