Weird protected access problem.

[=?gb2312?B?wfXquw==?=]

Hi, folks,
My g++ is of version 3.4.2, here is the code snippet:

#include <iostream>

using namespace std;

class Base {
protected:
Base() {
cout << "This is B\n";
}
};

template<typename T>
class Derived: public Base {
public:
Derived(){}
Derived(const Base& b): Base(b) {}

Derived<TD() {
Base b;
return Derived<T>(b);
}
};

int main() {
Derived<intobj;

obj.D();

return 1;
}

When I tried to build this program, an error arraised:

test.cpp:7: error: `Base::Base()' is protected
test.cpp:18: error: within this context

Any informative tips will be appreciated, thank you.

Best regards.