value initializing unions inside a struct

output from webcompiler.cloudapp.net

Compiled with /EHsc /nologo /W4
main.cpp

Compilation successful!

Total compilation time: 109ms

0 0 0 0 0 0 0 0 0 0 

50790056 50790132 50790220 49536592 -1801320171 -2 49555713 49555747 49683692 6 

Total execution time: 515ms

test.cpp

#include <iostream>
using namespace std;

union U
{
    int x;
    float y;
};
	
struct A
{
    U us[10]{};
};

int main()
{
    // array of union:
    // value init seems to zero out
    U us[10]{};
    for (U u : us)
    {
        cout << u.x << " ";
    }
    cout << "\n";

    // struct of array of union:
    // the array member is value initialized,
    // yet contains garbage initially.
    // Compiler bug? Spec bug? C++ shenanigans?
    A a;
    for (U u : a.us)
    {
        cout << u.x << " ";
    }
    cout << "\n";
}