Question

#include <iostream>
using namespace std;

int recur(int x) {
    1 and recur(--x);
    cout << x;
    return x;
}

int main() {
    recur(10);
    return 0;
}

Answer 1

1 and recur(--x);

is equivalent to

recur(--x);

Clearly you are making infinite recursive calls which leads to stack overflow followed by segmentation fault.

I guess you meant

  x and recur(--x);

which makes the recursive call only when x is non-zero.