Typedef struct X{X* pX;}X; - C (СИ)

#include <iostream>
 
struct thing {
    friend std::ostream& operator<< (std::ostream &os, const thing& t);
};
 
std::ostream& operator<< (std::ostream &os, const thing &t) {
    os << "thing";
    return os;
}
 
typedef int counter_t;
typedef thing thing_t;
 
int main() {
    counter_t a = counter_t();
    thing_t t = thing_t();
 
    std::cout << a << ' ' << t << ' ';
}