From cppreference.com
classthread::id;(since C++11)The class thread::id is a lightweight, trivially copyable class that serves as a unique identifier of
and
(since C++20) objects.
Instances of this class may also hold the special distinct value that does not represent any thread. Once a thread has finished, the value of std::thread::id may be reused by another thread.
This class is designed for use as key in associative containers, both ordered and unordered.
Member functions
constructs an id that does not represent a thread
(public member function)Non-member functions
Helper classes
See also
returns the id of the thread
(public member function)
(C++11)
returns the thread id of the current thread
(function)