foo.cc: In function ‘int main()’:
foo.cc:19:15: warning: unused variable ‘i’ [-Wunused-variable]
   19 |         int x,i;
      |               ^
foo.cc: In function ‘int f(int)’:
foo.cc:17:18: warning: control reaches end of non-void function [-Wreturn-type]
   17 |                 }}
      |                  ^