变量声明顺序和指针偏移问题示例

#include<iostream>
using namespace std;

void run();

int main() {
  run();
}

void run() {

  //int i2 = 555, i1 = 666; //if opened, the result will be 1, which is the space not allocated
  int i1= 555 , i2 = 666; //跟声明顺序有关，先声明的变量会先被分配到内存空间
  int* ptr = &i1;

  cout << &i1 << " : " << &i2 << endl;

  ptr--;
  int i3 = *ptr;
  cout << i3 << endl;//666
}