std::packaged_task<R(Args...)>:: valid

From cppreference.com
Concurrency support library
Threads
(C++11)
(C++20)
this_thread namespace
(C++11)
(C++11)
Cooperative cancellation
Mutual exclusion
Generic lock management
Condition variables
(C++11)
Semaphores
Latches and Barriers
(C++20)
(C++20)
Futures
(C++11)
(C++11)
(C++11)
Safe Reclamation
Hazard Pointers
Atomic types
(C++11)
(C++20)
Initialization of atomic types
(C++11) (deprecated in C++20)
(C++11) (deprecated in C++20)
Memory ordering
Free functions for atomic operations
Free functions for atomic flags
bool valid ( ) const noexcept ;
(since C++11)

Checks whether * this has a shared state.

Parameters

(none)

Return value

true if * this has a shared state, false otherwise.