C/C++中的const int*和int * const

代码：

 #include <iostream> 

 using namespace std; 

 int main(){
     const int *p;
     int a = ;
     p = &a;
     a = ;

     cout<<p<<" "<<*p<<endl;

     int b = ;
     p = &b;

     cout<<p<<" "<<*p<<endl;

     //*p = 1; 错误，不允许修改，*p是常量
     //cout<<*p<<endl;

     int * const p1 = &a;//此处必须初始化，否则编译错误
     cout<<p1<<" "<<*p1<<endl;

     //p1 = &b; 错误，不允许向常量指针赋值
     //cout<<p1<<" "<<*p1<<endl;

     const int * const p2 = &a;
     cout<<p2<<" "<<*p2<<endl;
     a = ;
     cout<<p2<<" "<<*p2<<endl;
     //*p2 = 290;
     //p2 = &b; 两者都不允许

     return ;
 }

输出：

0x7ffe6a0ecc34 5
0x7ffe6a0ecc30 10
0x7ffe6a0ecc34 5
0x7ffe6a0ecc34 5
0x7ffe6a0ecc34 100

需要注意的是const int是可以修改的，见以下代码：

 int main(){

     const int i = ;
     int *j = (int*)&i;
     *j = ;
     cout<<i<<" "<<*j<<endl;

     return ;
 }

输出：

0 1