函数重新声明是未定义的行为吗?

Code:

代码:

#include <iostream>
using namespace std;

int f(int x = 0) {
    cout << "x:" << x << endl;
    return 0;
}
int main() {
    f();
    int f(int x = 1);
    f();
    return 0;
}
#include <iostream>
using namespa