What is the purpose of weak_ptr in C++11?

What is the purpose of weak_ptr in C++11?

In C++11, weak_ptr is used to break circular references in shared_ptr, preventing memory leaks.

Can you give me an example of how to use weak_ptr?

Sure! Here's a simple example:

#include <iostream>
#include <memory>

class B; // Forward declaration

class A {
public:
    std::shared_ptr<B> b;
};

class B {
public:
    std::weak_ptr<A> a; // weak_ptr to avoid circular reference
};

int main() {
    std::shared_ptr<A> a = std::make_shared<A>();
    std::shared_ptr<B> b = std::make_shared<B>();
    a->b = b;
    b->a = a; // No circular reference
    return 0;
}

What happens if I try to access a weak_ptr?

If you try to access a weak_ptr directly, you'll need to convert it to a shared_ptr using the lock() method. If the object has been deleted, lock() will return a null shared_ptr.

Are there any performance implications of using weak_ptr?

Yes, using weak_ptr can have a slight overhead due to the need to manage the reference count, but it is generally negligible compared to the benefits of preventing memory leaks.