/in/foo.cc: In function 'int main()':
/in/foo.cc:21:3: warning: value computed is not used [-Wunused-value]
   *p++; //指针p指向下一个数组元素
   ^~~~
/in/foo.cc:7:7: warning: 'p' may be used uninitialized in this function [-Wmaybe-uninitialized]
  int *p;//定义一个指针，用来比较大小
       ^