关于使用引用类型所引起的错误

#include <iostream>using namespace std;struct node{    int val;    node* previous;    node* next;    void init(int n){        val = n;        previous = NULL;        next = NULL;    }}*head;//指针的引用// head->neck->tailvoid func(node* &p){    if(p->next == NULL){        return;    }    if(p->val == 2){        cout<<"p is neck"<<endl;     //最开始p为neck        p->previous->next = p->next;  //将head的next指针指向tail，表面上p没有改变；                                      // 然而实质上也改变了p，因为p=head->next，此时p指向的是tail        if(p->val == 3)            cout<<"p is tail"<<endl;         //p改为tail        p->next->previous = p->previous; //试图将tail的previous指针指向head，然而此时p为tail，p->next = NULL,报错    }else{        func(p->next);    }}int main(){    head = new node;    head->init(1);    head->next = new node;    node* neck = head->next;    neck->init(2);    neck->previous = head;    neck->next = new node;    node* tail = neck->next;    tail->init(3);    tail->previous = neck;    func(head);    delete head;    delete neck;    delete tail;    return 0;}

使用引用类型时要小心谨慎。