[英]Undefined Reference to Base Class Constructor
這是我的雙向鏈表的實現代碼,它從單個鏈表繼承了以前的代碼,我目前遇到了鏈接器錯誤的問題,過去一個小時在網上沖浪尋找我的問題的答案,但一無所獲遠幫我。 這是我最后的資源 誰能幫忙?
具體來說,當我嘗試使用 g++ 鏈接我的 .o 文件時出現的錯誤是:
DoublyList.o:DoublyList.cpp:(.text+0xf): undefined reference to
`LinkedList::LinkedList()'
collect2.exe: error: ld returned 1 exit status
我發現提出了非常相似的問題,但沒有一個答案對我有幫助,或者至少我不知道如何在我的代碼中具體實現它們,任何幫助都會得到認可。
#ifndef LINKEDLIST_H
#define LINKEDLIST_H
using namespace std;
struct node
{
float value;
node *next;
};
class LinkedList
{
private:
node *first;
public:
LinkedList();
virtual void insert(float val);
virtual void del(float val);
virtual void read();
virtual int search(float val);
};
#endif
#include <iostream>
#include "LinkedList.h"
using namespace std;
LinkedList::LinkedList()
{
this->first = NULL;
}
void LinkedList::insert(float val)
{
if(this->first==NULL or this->first->value >= val)
{
node* a_node = new node();
a_node->value = val;
this->first = a_node;
return;
}
node* n = new node();
n = this->first;
node* new_node = new node();
new_node->value = val;
while(n->next != NULL and n->next->value < new_node->value)
{
n = n->next;
}
new_node->next = n->next;
n->next = new_node;
}
void LinkedList::del(float val)
{
node* n = this->first;
node* prev = new node();
prev = n;//in case if it is the first value
int i = this->search(val);
if(this->first->value == val)
{
this->first = this->first->next;
return;
}
if(i != -1)
{
for(int j = 0; j < i; j++)
{
prev = n;
n = n->next;
}
}
//one last check
if(n->value == val)
{
prev->next = n->next;
}
}
void LinkedList::read()
{
node* n = this->first;
int i = 1;
while(n != NULL)
{
cout << i << ". " << n->value << endl;
n = n->next;
i++;
}
}
int LinkedList::search(float val)
{
int i = 0;
node* n = this->first;
while(n != NULL)
{
if(n->value == val)
return i;
else
{
n = n->next;
i++;
}
}
return -1;
}
#ifndef DOUBLYLIST_H
#define DOUBLYLIST_H
#include "LinkedList.h"
class DoublyList: public LinkedList
{
public:
struct node
{
float value;
node * next;
node * prev;
};
node * first;
DoublyList();
void insert(float val);
void del(float val);
void read();
int search(float val);
};
#endif
#include <cstddef>
#include "DoublyList.h"
#include "LinkedList.h"
using namespace std;
//constructor
DoublyList::DoublyList()
{
first = NULL;
}
//Insert a node into the correct position in the doubly linked list
void DoublyList::insert(float val)
{
//if linked list is empty or val <= the first node
if(this->first == NULL or this->first->value >= val)
{
node * a_node = new node();
a_node->value = val;//set node's value
//begin replacing and assigning pointers
a_node->next = this->first;
a_node->prev = NULL;
this->first = a_node;
return;
}
node * n = new node();
n = this->first;
node * new_node = new node();
new_node->value = val;
node * prev_node = new node();
while(n->next != NULL and n->next->value < new_node->value)
{
prev_node = n;
n = n->next;
}
prev_node->next = new_node;
new_node->next = n->next;
new_node->prev = prev_node;
n->next = new_node;
}
void DoublyList::del(float val)
{
node * n = this->first;
int i = this->search(val);
//if first node
if(this->first->value == val)
{
this->first = this->first->next;
this->first->prev = NULL;
return;
}
//if value found
if(i != -1)
{
for(int j = 0; j < i; j++)
{
n = n->next;
}
//if a middle node
if(n->value == val and n->next != NULL)
{
n->prev->next = n->next;
return;
}
//if last node
if(n->prev != NULL)
{
n->prev->next = n->next;
}
}
return;//value not found so return
}
void DoublyList::read() { }
int DoublyList::search(float val) { }
編輯:忘了提到這個錯誤特別發生在 DoublyList.cpp 的第 8 行,這是從以前的試驗中鏈接 .o 文件。 我用來調用鏈接器的命令是
g++ -g main2.cpp DoublyList.o
其中 main2.cpp 是包含我測試代碼的 main 函數的代碼。
感謝 xskxzr,解決方案是將 LinkedList.o 與所有其余的 .o 文件一起鏈接。 如果有人遇到同樣的問題,這就是答案。
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