int * get_arr() {
    int loc[] = { 1, 2, 3, 4, 5};
    return loc;   // NO!!! returns a dangling pointer
}

int get_size(int arr[]) {
    return sizeof(arr);   // NO!!! returns sizeof(int *)
}

std::array<int> get_arr() {
    std::array<int, 5> arr = { 1, 2, 3, 4, 5 };
    return arr;   // fine, returning an object by copy (probably elided)
}

int get_size(const std::array<int>& arr) {
    return arr.size();       // fine and was passed by reference: no copy involved
}