NAME¶

std::weak_ptr::expired - std::weak_ptr::expired

Synopsis¶

bool expired() const noexcept; (since C++11)

Equivalent to use_count() == 0. The destructor for the managed object may not yet
have been called, but this object's destruction is imminent (or may have already
happened).

Parameters¶

(none)

Return value¶

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

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¶

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

// Run this code

#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

See also¶

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)