除錯了一上午，搞了半天是這個g++編譯器本身的問題，模板類果然是個麻煩的傢伙。
  g++不支援模板類的分離編譯，因此模板的實現最好都些在.h檔案中，否則將出現undefined reference to XXXX 的錯誤。下面是一個出錯的例子，解決方法就是將unilinklist.c中的程式碼移到unilinklist.h中。
//unilinklist.h

#ifndef UNILINKLIST_H_INCLUDED
#define UNILINKLIST_H_INCLUDED template <typename T>
class Unilinklist
{
    public:
    typedef struct Node
        {
        Node *next ;
        T data;
        }Node;
     Unilinklist();
     Unilinklist(Unilinklist<T>& o_link);
     Unilinklist(T data, int length);
     ~Unilinklist();      int getlength();
     void* gethead();
     bool travelover();
     void copyself(Node** tothird);
     bool isempty();
     void add_back(T data);
     void del_back();
     bool insert(int pos, T data);     private:      Node* head ;
     Node* prevent;
     Node* end;
     int count ; }; template <typename T>
Unilinklist<T>::Unilinklist()
{
    prevent = end = head = new Node;
    count = 0;
}
template <typename T>
Unilinklist<T>::Unilinklist(T data, int length)
{
    count = 0;
    prevent = end = head = new Node;
    while(length-- > 0)
    {
        prevent = new Node;
        prevent->data = data;
        end->next = prevent;
        end = prevent;
        end->next = NULL;
        count++;
    }
}
template <typename T>
Unilinklist<T>::Unilinklist(Unilinklist<T>& o_link)
{
    count = 0;
    prevent = end = head = new Node;
    o_link.copyself(&head);
    end = prevent = head->next;
    while(prevent->next != NULL)
    {
        prevent = prevent->next;
        end = prevent;
        count++;
        //cout<< count << endl;
    }
    end->next = NULL;
}
template <typename T>
Unilinklist<T>::~Unilinklist()
{
    while (head->next != NULL)
    {
        del_back();
        //cout <<count<<endl;
    }
} template <typename T>
int Unilinklist<T>::getlength()
{
    return count;
}
template <typename T>
bool Unilinklist<T>::travelover()
{
    std::cout << "********The data is:*******" << std::endl;
    prevent = head->next;
    while (prevent == NULL)
        return false;     do
    {
        std::cout<<prevent->data<<std::endl;
        prevent = prevent->next;
    }
    while(prevent != NULL);
    std::cout << "*******The end************\n"<<std::endl;
    return true;
}
template <typename T>
void* Unilinklist<T>::gethead()
{
    return head;
}
template <typename T>
void Unilinklist<T>::copyself(Node** tothird)
{
    std::cout<<"Copy constructor is running"<<std::endl;
    Node* temp;
    Node* tempre;
    Node* tempend;
    temp = new Node;
    tempend = tempre= temp;
    prevent = head->next;
    while(prevent != NULL)
    {
        tempre = new Node;
        tempre->data = prevent->data;
        prevent = prevent->next;
        tempend->next = tempre;
        tempend = tempre;
        tempend->next = NULL;
    }     *tothird = temp;
    std::cout<<"Copy success"<<std::endl;
}
template <typename T>
bool Unilinklist<T>::isempty()
{
    return (head->next == NULL);
}
template <typename T>
void Unilinklist<T>::add_back(T data)
{
    prevent = new Node;
    prevent->data = data;
    end->next = prevent;
    end = prevent;
    end->next = NULL;
    count++;
}
template <typename T>
void Unilinklist<T>::del_back()
{
    prevent = head;
    while (prevent->next->next != NULL)
    {
        prevent = prevent->next;
    }
    if(prevent->next != NULL)
    {
        end = prevent;
        delete(prevent->next);
        end->next = NULL;
        count--;
    }
    // cout<<count<<endl; }
template <typename T>
bool Unilinklist<T>::insert(int pos, T data)
{
    if(pos > count)
    {
        std::cout<<"The position is wrong" <<std::endl;
        return false;
    }
    prevent = head;
    while(--pos != 0)
    {
        prevent = prevent->next;
    }
    Node* temp = new Node;
    temp->data = data;
    temp->next = prevent->next;
    prevent->next = temp;
    return true;
} #endif // UNILINKLIST_H_INCLUDED
 

//test.c

#include <iostream>
#include "unilinklist.h"

int main()
{
    std::cout << "Default Constructor:\n" << std::endl;
    Unilinklist<int> lk1(325, 6);
    lk1.add_back(1);
    lk1.add_back(2);
    lk1.add_back(8);
    lk1.add_back(9);
    lk1.add_back(88);
    lk1.insert(3, 3233539);
    lk1.travelover();
    lk1.del_back();
    lk1.travelover();
    Unilinklist<int>lk2 = lk1;
    lk2.travelover();
    lk2.del_back();
    lk2.travelover();

    return 0;
}