Under normal circumstances, define a pointer p pointing to an integer, define an integer variable i, assign it a value of 1, and then assign the variable to *p, that is, *p = i. At this time, the value of p and the value of *p are printed. They are the address of variable i and the value of i respectively. However, if the integer variable i is no longer defined, but the literal 1 is directly assigned to *p, then the return results of p and *p will be empty.

Case 1: Pointer results can be output

#include <iostream>
using namespace std;
int main() {
    int* p;
    int i = 1;
    *p = i;
    cout << p << endl;
    // 0xef16f0
    cout << *p << endl;
    // 1
    return 0;
}

Case 2: No return value

#include <iostream>
using namespace std;
int main() {
    int* p;
    *p = 1;
    cout << p << endl;
    // No return value
    cout << *p << endl;
    // No return value
    return 0;
}

I would like to ask for advice. What is the cause of this situation? What characteristics are based on pointers?