/in/foo.cc: In function 'int main()':
/in/foo.cc:6:15: warning: format '%lf' expects argument of type 'double*', but argument 2 has type 'double' [-Wformat=]
  scanf("%lf",x);
               ^
/in/foo.cc:6:7: warning: 'x' is used uninitialized in this function [-Wuninitialized]
  scanf("%lf",x);
  ~~~~~^~~~~~~~~