#include <iostream>
using namespace std;

int main() {
  int* ptr = new int;
  
  cout << "before: " << ptr << ":" << *ptr << endl; //這行拿掉就會crash
  delete ptr;
  *ptr     = 123;
  cout << "read after free: " << ptr << ":" << *ptr << endl;
  *ptr = 456; // write after free
  cout << "read after free: "<< ptr << ":" << *ptr << endl;
  return 0;
}