std::weak_ptr<T>::expired
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std::weak_ptr
Member functions
Modifiers
Observers
weak_ptr::expired
(C++26)
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(C++20)
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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).
Contents
[edit] Parameters
(none)
[edit] Return value
true if the managed object has already been deleted, false otherwise.
[edit] Notes
If the managed object is shared among threads, it is only meaningful when expired() returns true.
[edit] 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