Initialize aggregate as class member

Question

In this code:

#include <array>
#include <cstdint>

struct K {
    std::array<char, 4> a;
    std::uint8_t b;
};

const K k1 = { {'T', 'e', 's', 't'}, 1 };

class X {
    const K k2 = { {'A', 'b', 'c', 'd'}, 2 };
};

I can initialize a global object k1 just fine. But trying to use the same syntax on a default initializer of the class member k2 gives compiler errors (similar errors from g++-4.8.2 and g++-5.2.0):

main.cpp:12:44: error: array must be initialized with a brace-enclosed initializer
     const K k2 = { {'A', 'b', 'c', 'd'}, 2 };
                                            ^
main.cpp:12:44: error: too many initializers for 'std::array<char, 4ul>'

What's the correct way to initialize k2 at its declaration?

Answer 1

You just need an extra pair of braces:

class X {
    const K k2 = { {{'A', 'b', 'c', 'd'}}, 2 };
};