具有默认参数的initializer_list构造函数

Question

I define a initializer list ctor (sequence ctor) in a class and give it a default argument like this:

class Box 
{
public:
    Box(std::initializer_list<XMFLOAT3> vertices = {XMFLOAT3(), XMFLOAT3(), XMFLOAT3(), XMFLOAT3(), XMFLOAT3(), XMFLOAT3(), XMFLOAT3(), XMFLOAT3()});
    ~Box();
    void SetVertices(std::initializer_list<XMFLOAT3> vertices);
    XMFLOAT3 (&GetVertices())[8];
    Mesh &GetMesh() { return mMesh; }
private:
    XMFLOAT3 mVertices[8];
    Mesh mMesh;
};

but when I put an object of type Box inside another class the compiler complains that there's no default ctor available. Why?

EDIT if I call the default ctor into the containing class ctor's initialization list:

Bone::Bone(std::string const &name) : mName(name), mCollisionBox{}
{
}

(I understand that when an initializer_list ctor is present the brace notation calls the default ctor first, not the initializer_list ctor with an empty list) it calls the default ctor.

The default ctor is also called if I explicitly call it:

Bone::Bone(std::string const &name) : mName(name), mCollisionBox()
{
}

I'm using VisualC++ with Visual studio 2017 that's really strange..

EDIT 2

in this example it works, but as I pointed out on the commented line it doesn't in VS 2017

http://coliru.stacked-crooked.com/a/e1de3b215c6c4634

Answer 1

You are asking the wrong question - because it is perfectly legal what you are asking for. Could be the error is something else or you need to provide a minimal and complete example.