例如,对于以下代码片段:
#include <iostream>
using namespace std;
template <class T>
class A {
protected:
T value;
T getValue() { return value; }
public:
A(T value) { this->value = value; }
};
template <class T, template <class U> class A>
class B : protected A<T> {
public:
B() : A<T>(0) { /* Fake value */ }
void print(A<T>& input) {
cout << input.getValue() << endl;
}
};
int main(int argc, char *argv[]) {
B<int, A> b;
A<int> a(42);
b.print(a);
}
编译器(在OS X上是clang,但gcc返回相同类型的错误)返回以下错误:
Untitled.cpp:18:21: error: 'getValue' is a protected member of 'A<int>'
cout << input.getValue() << endl;
^
Untitled.cpp:25:5: note: in instantiation of member function 'B<int, A>::print' requested here
b.print(a);
^
Untitled.cpp:8:7: note: can only access this member on an object of type 'B<int, A>'
T getValue() { return value; }
^
1 error generated.
奇怪的是编译器的最后一条注释完全正确,但已经应用于类型为“B ”的对象“b”。这是编译器的错误还是代码存在问题?谢谢。