我一用 delete 就运行出错，何解？

[chl]

小弟做C++还是新手，做了个简单的链表，虽然插入、删除、等功能都实现了，但发现只要我的代码中一出现，如下注释了的 delete .. 就运行时报错了，请指点。

#include<iostream.h>

class Node
{
char* mesg;
Node* nextNode;
public :
Node(char* msg);
void setNode(Node* n);
Node* getNode();
char* getMesg();
~Node();
};

char* Node::getMesg(){
return mesg;
}

void Node::setNode(Node* n){
nextNode=n;
}

Node* Node::getNode(){
return nextNode;
}

Node::Node(char* msg)
{
mesg=msg;
nextNode=NULL;
}

Node::~Node(){
delete mesg;
delete nextNode;
cout<<"\n**node delet**\n";
}

// List started.

class List
{
Node* head,* tail;
unsigned int nCount;
void remove(Node* n);
public :
List();
int nodeCount();
void insert(unsigned int count,Node* n);
void add(Node* n);
void removeAll();
void delet(unsigned int count);
void show();
~List();
};

List::List(){
head=new Node("It's head here.");
tail=head;
head->setNode(NULL);
nCount=0;
}

List::~List(){
delete head;
delete tail;
cout<<"\n**delete List**\n";
}

void List::add(Node* n){
if(nCount==0){
head->setNode(n);
tail=n;
}
else{
tail->setNode(n);
tail=n;
}
tail->setNode(NULL);
nCount++;
}

void List::insert(unsigned int count,Node* n){
if(count==0){
cout<<"只从1开始。"<<endl;
return ;
}
if(count>nCount+1){
cout<<"没有那么多个节点。"<<endl;
return ;
}
if(count!=nCount+1){
Node* node=head;
for(unsigned int i=1;i<count;i++){
node=node->getNode();
}
n->setNode(node->getNode());
node->setNode(n);
List::nCount++;
}
else{List::add(n);}
}

void List::delet(unsigned int count){
if(count==0){
cout<<"从1开始。"<<endl;
return ;
}
if(count>nCount){
cout<<"没有那么多个节点。"<<endl;
return ;
}
if(count!=nCount){
Node* node=head;
for(unsigned int i=1;i<count;i++){
node=node->getNode();
}
Node* nn=node->getNode();
node->setNode(nn->getNode());
//delete nn;
nCount--;
}
else{
Node* node=head;
for(unsigned int i=1;i<nCount;i++){
node=node->getNode();
}
Node* nn=tail;
tail=node;
tail->setNode(NULL);
//delete nn;
nCount--;
}
}

void List::removeAll(){
tail=head;
List::remove(head->getNode());
nCount=0;
tail->setNode(NULL);
}

void List::remove(Node* n){
if(n->getNode()!=NULL) {
remove(n->getNode());
}
//delete n;
}

void List::show(){
if(head->getNode()==NULL){
cout<<"Nothing in it.\n";
return;
}
Node* n=head->getNode();
cout<<"\n";
while(n!=NULL){
cout<<" "<<n->getMesg();
n=n->getNode();
}
cout<<"\n\n";
}

//class finished, main method then.

main(){
List* l;
l=new List();
l->show();
Node * n1=new Node("1");
l->add(n1);
l->add(new Node("2"));
l->insert(3,new Node("3"));
l->show();
l->delet(3);
l->show();
l->removeAll();
l->show();
//delete n1;
//delete l;
return 1;
}

[chl]

help!

[zx_sanjin]

太长了吧~~~~~
对基本变量的指针, delete 与 delete[]可通用;
对类或或结构的指针, 就必须用delete[]~~~~~

[leizhengdeng]

For common variable and class, you should use delete;
for array of variable and class, you should use delete [].

[chl]

那我把它弄短些，希望大虾能够帮帮我。
如果在 main() 里面的"delete node"没被注释，也一样运行时出错，改成"delete[] node"也一样不行。究竟是什么回事？

#include<iostream.h>

class Node
{
char* mesg;
Node* nextNode;
public :
Node(char* msg);
void setNode(Node* n);
Node* getNode();
char* getMesg();
~Node();
};

char* Node::getMesg(){
return mesg;
}

void Node::setNode(Node* n){
nextNode=n;
}

Node* Node::getNode(){
return nextNode;
}

Node::Node(char* msg)
{
mesg=msg;
nextNode=NULL;
}

Node::~Node(){
delete mesg;
delete nextNode;
cout<<"\n**node delet**\n";
}

main(){
Node* node=new Node("hello");
cout<<"message:"<<node->getMesg()<<"\n";
//delete node;
return 1;
}

[hz129]

改成：
......
Node::Node(char* msg)
{
mesg = new char[strlen(msg)+1];
strcpy(mesg, msg);
nextNode=NULL;
}
......

你创建node的时候传进去的"hello"是一个const指针，它不是你自己用new创建的，但你的node删除的时候执行delete mesg;试图删除它，所以会出错。
new 和 delete必须成对出现。

[leizhengdeng]

同意楼上的
#include <iostream.h>
#include <string.h>

class Node
{
private:
char* mesg;
Node* nextNode;
public :
Node(char* msg);
~Node();
void setNode(Node* n);
Node* getNode();
char* getMesg();

};

char* Node::getMesg()
{
return mesg;
}

void Node::setNode(Node* node)
{
nextNode = node;
}

Node* Node::getNode()
{
return nextNode;
}

Node::Node(char* msg)
{
mesg = new char[strlen(msg)+1];
strcpy(mesg, msg);
nextNode=NULL;
}

Node::~Node()
{
if (mesg != NULL)
{
delete mesg;
}
if (nextNode != NULL)
{
delete nextNode;
}
cout<<"\n**node deleted**\n";
}

int main()
{
Node* node=new Node("hello");
cout<<"message:"<<node->getMesg()<<"\n";
delete node;
return 1;
}

[jellimy]

同意！
不是自己new的就不需要自己delete;delete之前判断参数是否为空。
对malloc和free同样适用。

[chl]

谢谢各位的帮助。以后还请多多指教。