Different output between GCC and MSVC. What is going on here?

main.cpp

#include <stdio.h>
#include <stdint.h>
#include <new>

struct Empty { }; // implicitly-defined default ctor

struct Foo : Empty
{
    uint8_t a;
    uint8_t b;
};

int main()
{
    printf("sizeof(Empty) = %lu\n", sizeof(Empty)); // == 1 on both GCC and MSVC.
    printf("sizeof(Foo) = %lu\n", sizeof(Foo));  // == 2

    uint8_t buffer[128];

    Foo* foo = (Foo*)buffer;
    foo->a = 1;
    foo->b = 2;

    Empty* ee = (Empty*)foo;
    ee = ::new(ee) Empty(); // Here MSVC initializes Empty with 0 and overrides foo.a !!

    printf("%d %d\n", foo->a, foo->b); // Outputs '1 2' on GCC but '0 2' on MSVC.

    return 0;
}

This apparently is the case on VS2013 and not on VS2015. Ref: https://twitter.com/GemsMarlo/status/871543098052161537