c – 派生纯虚函数的实现

#include <iostream>

struct PureVirtual {
    virtual void Function() = 0;
};

struct FunctionImpl {
    virtual void Function() {
        std::cout << "FunctionImpl::Function()" << std::endl;
    }   
};

struct NonPureVirtual : public FunctionImpl,public PureVirtual {
    using FunctionImpl::Function;
};

int main() {
    NonPureVirtual c;
    c.Function();
}

编译器(GCC 4.9,Clang 3.5)出现错误

test.cpp:18:20: error: variable type 'NonPureVirtual' is an abstract class
    NonPureVirtual c;
                   ^
test.cpp:4:18: note: unimplemented pure virtual method 'Function' in 'NonPureVirtual'
    virtual void Function() = 0;
                 ^

但是当我没有派生PureVirtual的形式时,一切都可以.这是奇怪的,因为标准10.4.4说

A class is abstract if it contains or inherits at least one pure
virtual function for which the final overrider is pure virtual.

他们并不在说什么是最终的覆盖者,但我认为它应该是FunctionImpl :: Function(),特别是当我通过使用指令可用.那么为什么还有NonPureVirtual抽象类,我该如何解决这个问题.