crazy unions

unions.c

enum student_t {
  STUDENT,
  GRADED_STUDENT
};

struct Student {
  char *name;
};

struct GradedStudent {
  struct Student student;
  int grade;
};

struct DynamicStudent {
  enum student_t student_type;
  union {
    Student student;
    GradedStudent graded_student;
  };
};