Introduction to smart pointers

Intuition

Smart pointers were created as wrappers around raw pointers to deal with two of the most common memory management problems: (i) Failing to deallocate memory appropriately leading to memory leaks (ii) Trying to access/deallocate already deallocated memory

Explanation

In order these problems, there exist 3 classes of smart pointers:

(i) auto_ptr/unique_ptr - This kind of pointer is focussed on the first problem and follows the exclusive ownership pattern. It deallocates when it goes out of scope. auto_ptr was the original class created for this purpose that got deprecated in C++11 and was replaced by unique_ptr.

(ii) shared_ptr - This pointer is focussed on the second problem and follows the shared ownership pattern. It maintains a count of the number of owners the memory has and only deallocates when all the owners relinquish control.

(iii) weak_ptr - This pointer takes a non-owning view on the object following the shared ownership pattern. IT can view the data but doesn't augment the count of the number of owners.

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#include <iostream>
#include <memory>

int main()
{
    std::unique_ptr<int> u_p = std::make_unique<int>(5);
    std::cout << *u_p << std::endl;

    std::shared_ptr<int> s_p = std::make_shared<int>(6);
    std::cout << *s_p << std::endl;

    std::weak_ptr<int> w_p = s_p;
    std::shared_ptr<int> temp_p = w_p.lock();

    std::cout << *temp_p << std::endl;

    return 0;
}

Goal

By the end of these series, you should understand and be able to implement smart pointer classes.