C ++ pointer references and pointers to pointers transport structures

#include <iostream>
using namespace std;

struct teacher {
	int id;
	char name[64];	
};

int tea(struct teacher* &a) {//指针引用，a是c的别名
	
	a = (struct teacher*)malloc(sizeof(struct teacher));//a = 开辟的内存，相当于c开辟内存，在写入数据
	if (a == NULL)
	{
		return -1;
	}
	a->id = 100;
	strcpy_s(a->name, "礼仪");
	return 0;
}

int tea1(struct teacher **a) {//指向指针的指针指向a(函数的实参)指针的取地址
	struct teacher *t = NULL;//a=实参的取地址，&a是a（指向指针的指针）的取地址，*a是a指向内存的内容
	if (a==NULL)             
	{
		return -1;
	}
	
	t = (struct teacher*)malloc(sizeof(struct teacher));//理解为某指针指向某地址，指针t = 某指针
	       
	//cout << t << endl;//t是一个指针，指向在内存中开辟的一个地址，t=某地址
	//cout << &t << endl;//&t是t自己的取地址
	//cout << a << endl;//
	//cout << *a << endl;
	//cout << &a << endl;
	//cout << &(*a) << endl;
	t->id = 100;	
	strcpy_s(t->name, "哈哈");
	*a = t;
	return 0;
}

void rea1(struct teacher **a) {
	if (a==NULL)
	{
		return;
	}
	struct teacher* t = *a;
	if (t!=NULL)
	{
		free(t);//开辟内存，要释放
		*a = NULL;		
	}
}

void rea(struct teacher *&a) {
	if (a==NULL)
	{
		return;
	}
	else
	{
		free(a); //开辟内存，要释放
		a = NULL;
	}
}

void main() {
	struct teacher *c = NULL;//定义一个指针作传输体

	tea1(&c);
	cout << "id=" <<c->id<<"名字:"<< c->name << endl;//极有可能是*(c->id)
	rea1(&c);
	tea(c);
	cout<< "id=" <<c->id<<"名字:"<< c->name << endl;
	rea(c);
}

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