/in/foo.cc:4:27: error: declaration of 'arr' as array of references
 void bubble_sort(int &arr[],int n)
                           ^
/in/foo.cc:4:28: error: expected ')' before ',' token
 void bubble_sort(int &arr[],int n)
                            ^
/in/foo.cc:4:29: error: expected unqualified-id before 'int'
 void bubble_sort(int &arr[],int n)
                             ^~~