c – 朋友类无法访问受保护的成员

此代码曾用于Visual Studio 2015,但它不再适用于Visual Studio 2015更新1.

class Foo
{
protected:

    virtual ~Foo() {};
    friend class Foo__init;
};

class Foo__init
{
public:

    Foo _init;
};

static Foo__init _Foo_init;

它失败并出现以下错误：

Error   C2248   'Foo::~Foo': cannot access protected member declared in class 'Foo'

这是编译器错误还是代码生成错误？

解决方法

从 here开始：

The friend declaration appears in a class body and grants a function or another class access to private and protected members of the class where the friend declaration appears.

所以这是一个编译器错误. g(Ubuntu 5.2.1-22ubuntu2)5.2.1 20151010和Ubuntu clang版本3.6.2-1(标签/ RELEASE_362 / final)(基于LLVM 3.6.2)编译此代码(我添加了int main(){} ).