类内静态成员初始化

Question

Given

struct X {};

constexpr auto x = X{};

struct S {
    static constexpr auto& rx = x;  
};

gcc 4.8 says

error: non-constant in-class initialization invalid for static member 'S::rx'

static constexpr auto& rx = x;  
                            ^

error: (an out of class initialization is required)

error: 'S::rx' cannot be initialized by a non-constant expression when being declared

I expect x to be a constant expression, suitable for such initialization. Is this a gcc bug? If not, what is going on here?

Answer 1

这是一个错误，似乎已经报道过了 。

Answer 2

You may do the below instead:

struct X {};

const auto x = X{};

struct S {
    static constexpr auto& rx = x;  
};