C ++私有虚拟继承问题 [英] C++ private virtual inheritance problem

问题描述

在下面的代码中，似乎C类不能访问A的构造函数，这是必需的，因为虚拟继承。然而，代码仍然编译和运行。为什么它可以工作？

In the following code, it seems class C does not have access to A's constructor, which is required because of the virtual inheritance. Yet, the code still compiles and runs. Why does it work?

class A {};
class B: private virtual A {};
class C: public B {};

int main() {
    C c;
    return 0;
}

<

Moreover, if I remove the default constructor from A, e.g.

class A {
public:
    A(int) {}
};
class B: private virtual A {
public:
    B() : A(3) {}
};

然后

class C: public B {};

会（意外）编译，但

class C: public B {
public:
    C() {}
};

无法正常编译。

使用g ++（GCC）3.4.4（cygming special，gdc 0.12，使用dmd 0.125）编译的代码，但已经验证其与其他编译器的行为相同。

Code compiled with "g++ (GCC) 3.4.4 (cygming special, gdc 0.12, using dmd 0.125)", but it has been verified to behave the same with other compilers as well.

推荐答案

根据 C ++无法从中衍生出具有虚拟专用库的Core Issue＃7 类。这是编译器中的错误。

According to C++ Core Issue #7 class with a virtual private base can't be derived from. This is a bug in compiler.

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