std::weak_ptr<T>::expired

bool expired() const noexcept;

(since C++11)
(constexpr since C++26)

Checks if the managed object has already been deleted. The destructor for the managed object may not yet have been called, but this object's destruction is imminent (or may have already happened).

Return value

use_count() == 0

Notes

If the managed object is shared among threads, it is only meaningful when expired() returns true.

Example

Demonstrates how expired is used to check validity of the pointer.

#include <iostream>
#include <memory>

std::weak_ptr<int> gw;

void f()
{
    if (!gw.expired())
            std::cout << "gw is valid\n";
    else
        std::cout << "gw is expired\n";
}
 
int main()
{
    {
        auto sp = std::make_shared<int>(42);
            gw = sp;
        f();
    }
    
    f();
}

Output:

gw is valid
gw is expired

lock	creates a `shared_ptr` that manages the referenced object (public member function)
use_count	returns the number of `shared_ptr` objects that manage the object (public member function)

std::weak_ptr<T>::expired

Return value

Notes

Example

See also