GDB C++11 failure

template <class T>
class Vector3t
{
public:
    T x;
    T y;
    T z;

    Vector3t(T _x = static_cast<T>(0.0), T _y = static_cast<T>(0.0), T _z = static_cast<T>(0.0));
    template <class U> auto operator+(const Vector3t<U> &a) const->Vector3t<decltype(T()*U())>;
};

template <class T>
inline Vector3t<T>::Vector3t(T _x, T _y, T _z) : x(_x), y(_y), z(_z)
{
}

template <class T> template <class U>
inline auto Vector3t<T>::operator+(const Vector3t<U> &a) const -> Vector3t<decltype(T()*U())>
{
    return Vector3t<decltype(T()*U())>(x + a.x, y + a.y, z + a.z);
}



void android_main(struct android_app* appState)
{
    Vector3t<float> vec1;
    Vector3t<float> vec2;

    auto vec3 = vec2 + vec1;

    int x = 0;

    while (1)
    {
        x++;
    }
}