What is std::weak_ptr and when is it used?

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Accepted Answer

**std::weak_ptr** — non-owning reference to shared_ptr-managed object. ```cpp #include // Breaking circular references class Node { public: std::shared_ptr next; std::weak_ptr prev; // weak to break cycle }; auto node1 = std::make_shared(); auto node2 = std::make_shared(); node1->next = node2; node2->prev = node1; // weak, doesn't increase count // Accessing weak_ptr std::weak_ptr wptr = sp1; if (auto locked = wptr.lock()) { // Object still alive std::cout << *locked; } else { // Object destroyed } // Check if expired if (wptr.expired()) { // Object is gone } ``` **Key points:** - Does not prevent destruction. - Must lock() before use. - Use to break circular references.

C++: What is std::weak_ptr and when is it used?