Question

可能重复：
  Why can templates only be implemented in the header file?
  Undefined reference to function template when used with string (GCC)
  C++ templates, undefined reference

我觉得我错过了一些链接C ++项目的东西。我不确定问题是在标题源中还是包含在内，所以我制作了一个最小的代码示例来演示它。

主要模块 minmain.cpp：

 #include <stdio.h>
 #include <vector>
 #include <string>
 #include "nodemin.h"

 using namespace std;

 int main()
 {
     // Blist libs are included
     Node<int>* ndNew = ndNew->Root(2);

     return 0;
 }

头文件 nodemin.h：

 #ifndef NODETEMP_H_
 #define NODETEMP_H_

 using namespace std;

 template<class T>
 class Node
 {
 protected:

    Node* m_ndFather;
    vector<Node*> m_vecSons;
    T m_Content;

    Node(Node* ndFather, T Content);

 public:

     // Creates a node to serve as a root
         static  Node<T>* Root(T RootTitle);
 };

 #endif

节点模块 nodemin.cpp：

 #include <iostream>
 #include <string.h>
 #include <vector>
 #include "nodemin.h"

 using namespace std;

 template <class T>
 Node<T>::Node(Node* ndFather, T Content)
 {
    this->m_ndFather = ndFather;
    this->m_Content = Content;
 }

 template <class T>
 Node<T>* Node<T>::Root(T RootTitle) { return(new Node(0, RootTitle)); }

编译行：

 #g++ -Wall -g mainmin.cpp nodemin.cpp

输出：

 /tmp/ccMI0eNd.o: In function `main':
 /home/******/projects/.../src/Node/mainmin.cpp:11: undefined reference to`Node<int>::Root(int)'
 collect2: error: ld returned 1 exit status

我尝试编译成对象，但链接仍然失败。

Answer 1

将template class Node<int>;添加到nodemin.cpp：

#include <iostream>
#include <string.h>
#include <vector>
#include "nodemin.h"

using namespace std;

template <class T>
Node<T>::Node(Node* ndFather, T Content)
{
   this->m_ndFather = ndFather;
   this->m_Content = Content;
}

template <class T>
Node<T>* Node<T>::Root(T RootTitle) { return(new Node(0, RootTitle)); }

template class Node<int>;

C ++链接失败，未定义引用

1 个答案: