/in/foo.cc:12:12: error: variable or field 'ping' declared void
 void ping(x)
            ^
/in/foo.cc:12:11: error: 'x' was not declared in this scope
 void ping(x)
           ^
/in/foo.cc: In function 'bool comp(Point, Point)':
/in/foo.cc:11:1: warning: control reaches end of non-void function [-Wreturn-type]
 }
 ^