Let's say I have two unrelated structs A and B which have exactly the same data members and everything. Checked with a static assert like this:

template
constexpr bool CheckCompatibility() noexcept
{
    static_assert(sizeof(From) == sizeof(To));
    static_assert(alignof(From) == alignof(To));

    static_assert(std::is_standard_layout_v);
    static_assert(std::is_standard_layout_v);

    static_assert(std::is_trivially_destructible_v);
    static_assert(std::is_trivially_destructible_v);

    static_assert(std::is_trivially_copyable_v);
    static_assert(std::is_trivially_copyable_v);

    return true;
}

Would this be allowed or UB?

struct A{
    int x,
    float y,
    double z,
    int arr[3];
};


struct B{
    int x,
    float y,
    double z,
    int arr[3];
};

A* a = new A();
B* b = reinterpret_cast(a);

// Using a & b (with proper synchronization and so on)