C++ :: Initializing A POD Bitfield Struct?

I'm wondering what is the "best" way to initialize a bitfield struct. I have this bitfield, defined as:

Code:
struct S
{
unsigned int a : 1;
unsigned int b : 1;
};

If I'm "using" the bitfield, I can initialize it easily when declaring it, as so:

Code:
int main()
{
S s = {0};
}

Now, the issue I'm facing is that I want to embed S inside another struct, which I'll name "outer". EG:

Code:
struct Outer
{
S s;
};

I'm wondering what the "best" way to have Outer initialize S is? I've seen a lot of people use the "union" approach:

Code:
struct Outer
{
Outer()
{
u.all = 0;
}
union
{
unsigned char all;
S s;
} u;
};

but:This adds an extra field depth (the union's u)Does bit hacking, in a way (is the bitfield as large as my field?) I'd have wanted to initialize the field in my constructor, as so:

Code:
Outer::Outer() : s({0})

However, this would appear to be a C++11 feature only.

I have, however, "observed" that by simply "empty constructing" s, eg:

Code:
Outer::Outer() : s(){} //Initialize s ?
vs
Outer::Outer(){}

Then my bitfield "appears" initialized.