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std::weak_ptr::expired(3) | C++ Standard Libary | std::weak_ptr::expired(3) |
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)
2024.06.10 | http://cppreference.com |