为什么这段代码运行报错啊？

C/C++ code

//Listing 10.10//operator++ returns a nameless temporary object#include <iostream>using namespace std;class Counter{public:    Counter();    Counter(int val);    ~Counter(){}    int GetItsVal() const {return itsVal;}    void SetItsVal(int x) {itsVal = x;}    void Increment() {++itsVal;}    Counter operator ++() {}private:    int itsVal;};Counter::Counter():itsVal(0){}Counter::Counter(int val):itsVal(val){}Counter Counter::operator ++(){    ++itsVal;    return Counter(itsVal);}int main(){    Counter i;    cout<<"The value of i is "<<i.GetItsVal()<<endl;    i.Increment();    cout<<"The value of i is "<<i.GetItsVal()<<endl;    ++i;    cout<<"The value of i is "<<i.GetItsVal()<<endl;    Counter a = ++i;    cout<<"The value of a: "<<a.GetItsVal();    cout<<" and i: "<<i.GetItsVal()<<endl;    return 0;}

[解决办法]
Counter operator ++() {} //已经定义了函数，不过是空的。。
=》Counter operator ++()；
[解决办法]
楼上说得对，Counter operator ++() {} 是一个inline成员函数了，再次定义会冲突