不会生成模板中的虚拟方法

可能的重复：
为什么使用模板时出现"未解析的外部符号"错误？

我有一套有点复杂的课程。
具有子参数化 A 类的类 _A，该类有两个子级 A1 和 A2。
类 B. 包含作为成员的类_A对象的指针。有两个子类 B1 和 B2，分别对应于类 A1 和 A2。B1 将_A构造为 A1。B2 作为 A2 尊重。
最后是类 Y，它在类 B 中定义了子 BY.
现在它是如何在文件中存在的。

TF1.h

#include <iostream>
struct Y{ // goes to the file tf2.h as ancestor of the class B::BY
};

struct _A{ // goes to the file tf2.h as a member of the class B
};
template<class X>
struct A: public _A {  // goes to two classes below only as an ancestor
virtual void method();
protected:
virtual void m() = 0;
};
template<class X>
struct A1: public A<X>{  // goes to the file tf2.h to the class B1
protected:
void m();
};
template<class X>
struct A2: public A<X>{  // goes to the file tf2.h to the class B2
protected:
void m();
};

TF1.cpp

#include "tf1.h"

template<class X>
void A<X>::method(){
/* here the class X used */
std::cout << "A::method called" << std::endl;
m();
}
template<class X>
void A1<X>::m(){
std::cout << "A1::m called" << std::endl;
}
template<class X>
void A2<X>::m(){
std::cout << "A1::m called" << std::endl;
}

TF2.h

#include "tf1.h"
class B{   // is the counterpain of the class _A
protected:
class BY: public Y{
};
_A * mp_x;
};

class B1: public B{  // is the counterpain of the class A1
public:
B1(){mp_x = new A1<BY>; std::cout << "B::B is called" << std::endl;}
};
class B2: public B{  // is the counterpain of the class A2
public:
B2(){mp_x = new A2<BY>; std::cout << "C::C is called" << std::endl;}
};

TFMAIN.cpp

#include <stdlib.h>
#include "tf2.h"
int main (int,char**){
B2 b2;
system ("PAUSE");
}

最后，问题。

d:>g++ -std=c++0x tfmain.cpp -o tfmain.exe
ccB2BnSP.o:tfmain.cpp:(.rdata$_ZTV2A2IN1B2BYEE[__ZTV2A2IN1B2BYEE]+0x8): undefined reference to `A<B::BY>::method()'
ccB2BnSP.o:tfmain.cpp:(.rdata$_ZTV2A2IN1B2BYEE[__ZTV2A2IN1B2BYEE]+0xc): undefined reference to `A2<B::BY>::m()'
ccB2BnSP.o:tfmain.cpp:(.rdata$_ZTV1AIN1B2BYEE[__ZTV1AIN1B2BYEE]+0x8): undefined reference to `A<B::BY>::method()

我正在使用 MinGW v4.7.2