클래스 템플릿을 상속할 때 기본 클래스의 공용 멤버가 보이지 않는 이유는 무엇이며, 이 문제에 대한 해결책은 무엇입니까?

<code class="cpp">class CBase
{
public:
    int Fn1(void) { ... }
};

class CDerived : public CBase
{
public:
    int FnSum(void) { ... CBase::Fn1(); ... }
};</code>

<code class="cpp">template<unsigned int BYTES>
class CBase
{
public:
    int Fn1(void) { ... }
};

template<unsigned int BYTES>
class CDerived : public CBase<BYTES>
{
public:
    int FnSum(void) { ... Fn1(); ... } // Error: Fn1 not found!
};</code>

<code class="cpp">int FnSum(void) {
    return CBase<BYTES>::Fn1() + CBase<BYTES>::Fn2() + CBase<BYTES>::Arr[0];
}</code>

<code class="cpp">int FnSum(void) {
    return this->Fn1() + this->Fn2() + this->Arr[0];
}</code>

<code class="cpp">using CBase<BYTES>::Arr;
using CBase<BYTES>::Fn1;
using CBase<BYTES>::Fn2;</code>

<code class="cpp">// Compiler flags: /permissive- (MSVC), -fpermissive (GCC/Cl), -fno-implicit-templates (Clang)</code>

<code class="cpp">#include <boost/preprocessor.hpp>

#define USING_ONE(r, base, member) using base::member;

#define USING_ALL(base, ...) BOOST_PP_SEQ_FOR_EACH(USING_ONE, base, BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__))

#define USING_CBASE(param) USING_ALL(CBase<param>, Arr, Fn1, Fn2, Fn3, Fn4, Fn5)</code>

<code class="cpp">USING_CBASE(BYTES); // Makes all mentioned CBase members directly accessible</code>