duck.cpp: In function ‘void changeX(int&)’:
duck.cpp:5: error: invalid type argument of ‘unary *’
duck.cpp: In function ‘int main()’:
duck.cpp:12: error: invalid initialization of reference of type ‘int&’ from expression of type ‘int*’
duck.cpp:4: error: in passing argument 1 of ‘void changeX(int&)’