Does std::array default-initialize or value-initialize?

Question

According to cppreference, std::array\'s constructor performs default-initialization when an std::array is created. However, when I\'m doing some t

Answer 1

std::array is an aggregate, it does not have constructors (and that's intentional). So when default-initialised, it default-initialises its elements. When value-initialised, it value-initialises them.

To analyse your code:

std::array<int, 3> arr1;  // gives me some garbage values, as expected
auto arr2 = std::array<int, 3>();  // gives me three 0, value-initialize?

arr1 is default-initialised. arr2 is copy-initialised from a temporary which was initialised with (), i.e. value-initialised.

Container() {}

This leaves the member arr default-initialised.

Container():
    arr()  // arr contains 0, 0, 0
{}

This initialises arr using (), which is value-initialisation.

Container() :
    arr{ 0, 1, 2 }
{}

This is legal C++11, but VS 2013 apparently doesn't support it (its C++11 support is incomplete).