如何多次繼承相同的 class？

Question

是否可以像這樣繼承兩個相同的類？ 我能夠在 msvc 上編譯它，但無法在 g++/clang++ 上編譯。 我收到錯誤：

Source.cpp:14:12: warning: direct base 'a' is inaccessible due to ambiguity:
    struct b -> struct a
    struct b -> class_combiner<struct a> -> struct a [-Winaccessible-base]
struct b : public a, public class_combiner<a> {
           ^~~~~~~~
Source.cpp:17:12: error: ambiguous conversion from derived class 'b' to base class 'a':
    struct b -> struct a
    struct b -> class_combiner<struct a> -> struct a
        a::f();

資源：

template <typename T>
struct class_combiner : public T {

    using T::T;

};

struct a {

    void f() {}

};

struct b : public a, public class_combiner<a> {

    void f2() {
        a::f();
        b::class_combiner::f();
    }

};


int main() {
    b x;
    x.f2();
}

Answer 1

我想出了可行的快速修復：

template <typename T, unsigned int instance>
struct class_combiner : public T {

    using T::T;

};

struct a {

    void f() {}

};

struct b : public class_combiner<a, 0>, public class_combiner<a, 1> {

    void f2() {
        class_combiner<a, 0>::f();
        class_combiner<a, 1>::f();
    }

};


int main() {
    b x;
    x.f2();
}