std::weak_ptr::expired

std::weak_ptr::expired

bool expired() const;

Checks whether the managed object has already been deleted. Equivalent to use_count() == 0.

Parameters

(none).

Return value

true if the managed object has already been deleted, false otherwise.

Exceptions

Notes

This function is inherently racy if the managed object is shared among threads. In particular, a false result may become stale before it can be used. A true result is reliable.

Example

#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();
}

gw is valid
gw is expired

See also