Question

Consider this code:

using namespace std;

int* get()
{
    unique_ptr<int> p (new int[4]);
    return p.get();
}
int main(int argc, char **argv)
{
    int *arr1=get();
    int* arr2=get();
    for(int i=0;i<4;i++)
    {
        arr1[i]=i;
        arr2[i]=i*2;
    }
    for(int i=0;i<4;i++)
        cout << arr1[i];
    return 0;
}

arr1 and arr2 point to the same area of memory.
So they share the same values.
I don’t understand why, when I call arr2=get() :

unique_ptr<int> p (new int[4]);

This object shouldn’t be created again? It isn’t deleted because still reachable by arr1.
How to get two arrays of different memory areas?

Answer 1

I am fairly sure you are playing with undefined behavior which is bad.

the data being pointed to was destroyed when the unique pointer was destroyed, the fact the values are the same, and the same slot was chosen is luck.

for pointers to array type use a vector

std::vector<int> get()
{
    return std::vector<int>(4);
}

int main()
{ 
    std::vector<int> arr1=get();
    std::vector<int> arr2=get();
    return 0;
}

for normal single value pointers then you can return a unique_ptr;

std::unique_ptr<int> get(){
    return std::unique_ptr<int>(new int(0));
}
:::
std::unique_ptr<int> ptr=get();