/in/foo.c:1:18: error: 'i' undeclared here (not in a function)
    1 | int num = 0, j = i + 1;
      |                  ^
/in/foo.c:2:1: error: expected identifier or '(' before 'while'
    2 | while (s[j] != '\0') {
      | ^~~~~
/in/foo.c:6:1: warning: data definition has no type or storage class
    6 | b = num;
      | ^
/in/foo.c:6:1: warning: type defaults to 'int' in declaration of 'b' [-Wimplicit-int]
/in/foo.c:6:5: error: initializer element is not constant
    6 | b = num;
      |     ^~~