std::weak_ptr<T>:: ~weak_ptr

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C++
Utilities library
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Relational operators (deprecated in C++20)
Dynamic memory management
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(C++11) (until C++23)
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(C++11) (until C++23)



std::weak_ptr
~weak_ptr ( ) ;
(since C++11)

Destroys the weak_ptr object. Results in no effect to the managed object.

Example

The program shows the effect of "non-breaking" the cycle of std::shared_ptr s.

Run this code 
#include <iostream>
#include <memory>
#include <variant>
 
class Node
{
    char id;
    std::variant<std::weak_ptr<Node>, std::shared_ptr<Node>> ptr;
public:
    Node(char id) : id{id} {}
    ~Node() { std::cout << "  '" << id << "' reclaimed\n"; }
    /*...*/
    void assign(std::weak_ptr<Node> p) { ptr = p; }
    void assign(std::shared_ptr<Node> p) { ptr = p; }
};
 
enum class shared { all, some };
 
void test_cyclic_graph(const shared x)
{
    auto A = std::make_shared<Node>('A');
    auto B = std::make_shared<Node>('B');
    auto C = std::make_shared<Node>('C');
 
    A->assign(B);
    B->assign(C);
 
    if (shared::all == x)
    {
        C->assign(A);
        std::cout << "All links are shared pointers";
    }
    else
    {
        C->assign(std::weak_ptr<Node>(A));
        std::cout << "One link is a weak_ptr";
    }
    /*...*/
    std::cout << "\nLeaving...\n";
}
 
int main()
{
    test_cyclic_graph(shared::some);
    test_cyclic_graph(shared::all); // produces a memory leak
}

Output: 

One link is a weak_ptr
Leaving...
  'A' reclaimed
  'B' reclaimed
  'C' reclaimed
All links are shared pointers
Leaving...

See also

destructs the owned object if no more shared_ptr s link to it
(public member function of std::shared_ptr<T> )
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