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#include <iostream>

using namespace std;

struct Teacher
{
char name[64];
int age;

};

//在被调用函数 获取资源
int getTeacher(Teacher **p)
{
if (p == NULL)
{
return - 1;
}
Teacher *tmp = NULL;
tmp = (Teacher*)malloc(sizeof(Teacher));
if (tmp == NULL)
{
return -2;
}
tmp->age = 20;
*p = tmp;
}

int getTeacher1(Teacher*& p)
{
//给p赋值，相当于给main函数中的pt赋值
p = (Teacher*)malloc(sizeof(Teacher));
if (p == NULL)
{
return -1;
}
p->age = 30;
}

void FreeTeacher(Teacher* tmp)
{
if (tmp == NULL)
{
return;
}
free(tmp);
}

void main()
{
Teacher *pt = NULL;
//C语言中的二级指针
getTeacher(&pt);
cout << "age:" << pt->age << endl;
FreeTeacher(pt);

//C++中的引用（指针引用）
getTeacher1(pt);//引用的本质 间接赋值后2个条件 让C++编译器帮我们做了
cout << "age:" << pt->age << endl;
FreeTeacher(pt);
system("pause");
}

 

 

    //引用：一个指针常量（常指针）
    //常引用：是让变量引用只读属性，y不能修改x
    int x = 20;
    const int &y = x;

    const int a = 10;//C++编译器把a放在符号表中
    const int& m = 11;//C++编译器会分配内存空间

    1）常引用const int &e相当于 const int* const e
    2)普通引用 int &e 相当于 int* const e