Function local static function-object that's initialized by lambda, thread-safe or not?

Is the following function thread-safe? And if it's not thread-safe, then is there really any overhead in making that funImpl non-static? Or does the compiler actually inline that function-object function and skip creating the function object altogether?

int myfun(std::array<int, 10> values)
{
    static const auto funImpl = [&]() -> int
    {
        int sum = 0;

        for (int i = 0; i < 10; ++i)
        {
            sum += values[i];
        }
        return sum;
    };

    return funImpl();
}

EDIT: I edited the function signature from:

int myfun(const std::array<int, 10>& values)

to:

int myfun(std::array<int, 10> values)

so that it is clear that I'm not asking about the tread-safety of values, but the thread-safety of the function local static variable funImpl.