使用模板访问 C++ 中超类的受保护成员

Why can't a C++ compiler recognize that g() and b are inherited members of Superclass as seen in this code:

template<typename T> struct Superclass {
 protected:
  int b;
  void g() {}
};

template<typename T> struct Subclass : public Superclass<T> {
  void f() {
    g(); // compiler error: uncategorized
    b = 3; // compiler error: unrecognized
  }
};

如果我简化 Subclass 并且只是从 Subclass 继承然后它编译.当将 g() 完全限定为 Superclass::g() 和 Superclass::b 时，它也会编译.我使用的是 LLVM GCC 4.2.

template<typename T> struct Subclass : public Superclass<T> {
  using Superclass<T>::b;
  using Superclass<T>::g;

  void f() {
    g();
    b = 3;
  }
};

template<typename T> struct Subclass : public Superclass<T> {
  void f() {
    this->g();
    this->b = 3;
  }
};