我已经为实践目的实现了一个C ++ STL列表（显然所有构造函数和方法都不存在）。大多数功能都正常工作。
#ifndef list_H
#define list_H
#include <iostream>
#include <stdexcept>
template <typename T>
class list {
public:
list <T> & operator = (const list<T> &);
~list();
/* Modifiers */
void push_back(T&& data);
void push_back(T const& data);
void push_front(T&& data);
void push_front(T const& data);
void pop_back();
void pop_front();
void swap(list &x);
void clear();
/* Iterators */
typedef T* iterator;
typedef T* const const_iterator;
const_iterator begin() const; // cbegin
iterator begin();
const_iterator end() const; //cend()
iterator end();
const_iterator rbegin() const;
iterator rbegin();
const_iterator rend() const;
iterator rend();
/* Capacity */
size_t size() const;
bool empty() const;
/* Element Access */
T& front();
T const& front() const;
T& back();
T const& back() const;
T& at(T const indx);
T const& at(T const indx) const;
T& operator[] (T const indx);
T const& operator[] (T const indx) const;
private:
struct node {
int data;
node *next, *prev;
node(T const& data, node* next, node* prev)
: data(data)
, next(next)
, prev(prev) {
}
node(T&& data, node* next, node* prev)
: data(std::move(data))
, next(next)
, prev(prev) {
}
};
int elements = 0;
node *head = nullptr;
node *tail = nullptr;
};
template <typename T>
list <T> & list<T>::operator = (const list<T> & that) {
node* tmp = head;
while(head) {
tmp = head;
head = head->next;
delete tmp;
}
elements = that.elements;
head = that.head;
tail = that.tail;
}
template <typename T>
list <T>::~list() {
node* tmp;
while(head) {
tmp = head;
head = head->next;
delete tmp;
}
}
template <typename T>
T& list<T>:: front() {
if(head == nullptr)
throw std::runtime_error("Invalid Action!");
return head->data;
}
template <typename T>
T const& list<T>:: front() const {
if(head == nullptr)
throw std::runtime_error("Invalid Action!");
return head->data;
}
template <typename T>
T& list<T>:: back() {
if(tail == nullptr)
throw std::runtime_error("Invalid Action!");
return tail->data;
}
template <typename T>
T const& list<T>:: back() const {
if(tail == nullptr)
throw std::runtime_error("Invalid Action!");
return tail->data;
}
template <typename T>
void list<T>::push_back(T const& data) {
node* newNode = new node(data, nullptr, tail);
if(head == nullptr)
head = newNode;
if(tail != nullptr)
tail->next = newNode;
tail = newNode;
++elements;
}
template <typename T>
void list<T>::push_back(T&& data) {
node* newNode = new node(std::move(data), nullptr, tail);
if(head == nullptr)
head = newNode;
if(tail != nullptr)
tail->next = newNode;
tail = newNode;
++elements;
}
template <typename T>
void list<T>::push_front(T const& data) {
node* newNode = new node(data, head, nullptr);
if(tail == nullptr)
tail = newNode;
if(head != nullptr)
head->prev = newNode;
head = newNode;
++elements;
}
template <typename T>
void list<T>::push_front(T&& data) {
node* newNode = new node(data, head, nullptr);
if(tail == nullptr)
tail = newNode;
if(head != nullptr)
head->prev = newNode;
head = newNode;
++elements;
}
template <typename T>
void list<T>::pop_front() {
if(head == nullptr)
throw std::runtime_error("Invalid Action");
node *tmp = head;
head = head->next;
if(head != nullptr)
head->prev = nullptr;
--elements;
delete tmp;
}
template <typename T>
void list<T>::pop_back() {
if(tail == nullptr)
throw std::runtime_error("Invalid Action");
node *tmp = tail;
tail = tail->prev;
if(tail != nullptr)
tail->next = nullptr;
--elements;
delete tmp;
}
template <typename T>
bool list<T>::empty() const {
return head == nullptr;
}
template <typename T>
size_t list<T>::size() const {
return elements;
}
template <typename T>
T& list<T>::operator[] (T const indx) {
int cont = 0;
node *curr = head;
while(curr) {
if(cont == indx)
return curr->data;
curr = curr->next;
++cont;
}
return nullptr;
}
template <typename T>
T const& list<T>::operator[] (T const indx) const {
int cont = 0;
node *curr = head;
while(curr) {
if(cont == indx)
return curr->data;
curr = curr->next;
++cont;
}
return nullptr;
}
template <typename T>
T& list<T>::at(T const indx) {
int cont = 0;
node *curr = head;
while(curr) {
if(cont == indx)
return curr->data;
curr = curr->next;
}
return nullptr;
}
template <typename T>
T const& list<T>::at(T const indx) const {
int cont = 0;
node *curr = head;
while(curr) {
if(cont == indx)
return curr->data;
curr = curr->next;
}
return nullptr;
}
template <typename T>
typename list<T>::const_iterator list<T>::begin() const {
return head;
}
template <typename T>
typename list<T>::iterator list<T>::begin() {
return head;
}
template <typename T>
typename list<T>::const_iterator list<T>::end() const {
return tail;
}
template <typename T>
typename list<T>::const_iterator list<T>::rbegin() const {
return tail;
}
template <typename T>
typename list<T>::iterator list<T>::rbegin() {
return tail;
}
template <typename T>
typename list<T>::const_iterator list<T>::rend() const {
return head;
}
template <typename T>
typename list<T>::iterator list<T>::rend() {
return head;
}
template <typename T>
typename list<T>::iterator list<T>::end() {
return tail;
}
template <typename T>
void list<T>::swap(list &that) {
std::swap(head, that.head);
std::swap(tail, that.tail);
std::swap(elements, that.elements);
}
template <typename T>
void list<T>::clear() {
node* curr = head;
while(head) {
curr = head;
head = head->next;
delete curr;
}
head = tail = nullptr;
elements = 0;
}
#endif // list_H
然后我通过以下方式测试了这个程序：
int main(void) {
deque<int> dq;
dq.push_back(1);
dq.push_back(2);
dq.push_back(3);
while(!dq.empty()) {
int value = dq.back();
std::cout << value << std::endl;
dq.pop_back();
}
return 0;
}
嗯，输出是：
3
2
1
但该程序并未终止于我的代码:: blocks 。
然后我用Ideone编译它，输出是：
3
2
1
*** Error in `./prog': double free or corruption (fasttop): 0x08923008 ***
======= Backtrace: =========
/lib/i386-linux-gnu/i686/cmov/libc.so.6(+0x75e72)[0xb75f8e72]
/lib/i386-linux-gnu/i686/cmov/libc.so.6(+0x76bb0)[0xb75f9bb0]
/usr/lib/i386-linux-gnu/libstdc++.so.6(_ZdlPv+0x1f)[0xb77db82f]
./prog[0x8048a17]
/lib/i386-linux-gnu/i686/cmov/libc.so.6(__libc_start_main+0xf5)[0xb759c8f5]
./prog[0x8048b41]
======= Memory map: ========
08048000-08049000 r-xp 00000000 09:03 16269491 /home/TKjJyD/prog
08049000-0804a000 rw-p 00001000 09:03 16269491 /home/TKjJyD/prog
08923000-08944000 rw-p 00000000 00:00 0 [heap]
b7581000-b7583000 rw-p 00000000 00:00 0
b7583000-b772c000 r-xp 00000000 09:03 16394299 /lib/i386-linux-gnu/i686/cmov/libc-2.17.so
b772c000-b772d000 ---p 001a9000 09:03 16394299 /lib/i386-linux-gnu/i686/cmov/libc-2.17.so
b772d000-b772f000 r--p 001a9000 09:03 16394299 /lib/i386-linux-gnu/i686/cmov/libc-2.17.so
b772f000-b7730000 rw-p 001ab000 09:03 16394299 /lib/i386-linux-gnu/i686/cmov/libc-2.17.so
b7730000-b7733000 rw-p 00000000 00:00 0
b7733000-b774e000 r-xp 00000000 09:03 16394343 /lib/i386-linux-gnu/libgcc_s.so.1
b774e000-b774f000 rw-p 0001a000 09:03 16394343 /lib/i386-linux-gnu/libgcc_s.so.1
b774f000-b7750000 rw-p 00000000 00:00 0
b7750000-b7791000 r-xp 00000000 09:03 16394296 /lib/i386-linux-gnu/i686/cmov/libm-2.17.so
b7791000-b7792000 r--p 00040000 09:03 16394296 /lib/i386-linux-gnu/i686/cmov/libm-2.17.so
b7792000-b7793000 rw-p 00041000 09:03 16394296 /lib/i386-linux-gnu/i686/cmov/libm-2.17.so
b7793000-b786f000 r-xp 00000000 09:03 16679929 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.18
b786f000-b7870000 ---p 000dc000 09:03 16679929 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.18
b7870000-b7874000 r--p 000dc000 09:03 16679929 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.18
b7874000-b7875000 rw-p 000e0000 09:03 16679929 /usr/lib/i386-linux-gnu/libstdc++.so.6.0.18
b7875000-b787c000 rw-p 00000000 00:00 0
b787e000-b7882000 rw-p 00000000 00:00 0
b7882000-b7883000 r-xp 00000000 00:00 0 [vdso]
b7883000-b78a2000 r-xp 00000000 09:03 16394256 /lib/i386-linux-gnu/ld-2.17.so
b78a2000-b78a3000 r--p 0001f000 09:03 16394256 /lib/i386-linux-gnu/ld-2.17.so
b78a3000-b78a4000 rw-p 00020000 09:03 16394256 /lib/i386-linux-gnu/ld-2.17.so
bfa1b000-bfa3c000 rw-p 00000000 00:00 0 [stack]
我认为问题出在pop_back()函数中。谁能知道发生了什么？
提前谢谢！
答案 0 :(得分：8)
pop_back需要使head无效;否则，析构函数将使用悬空head指针尝试删除已删除的节点。
赋值运算符也存在一个问题：它会生成一个＆＃34;浅拷贝＆＃34;其他列表的指针，以便两个列表都认为它们拥有（并尝试删除）相同的节点。
（此外，这更接近list而不是deque。一个deque应该允许在固定时间内随机访问;链接列表实现不允许这样做。）