std::thread::joinable
bool joinable() const noexcept; |
(since C++11) |
Checks if the std::thread
object identifies an active thread of execution. Specifically, returns true
if get_id() != std::thread::id()
. So a default constructed thread is not joinable.
A thread that has finished executing code, but has not yet been joined is still considered an active thread of execution and is therefore joinable.
Parameters
(none).
Return value
true
if the thread object identifies an active thread of execution, false
otherwise.
Example
#include <iostream> #include <thread> #include <chrono> void foo() { std::this_thread::sleep_for(std::chrono::seconds(1)); } int main() { std::thread t; std::cout << "before starting, joinable: " << std::boolalpha << t.joinable() << '\n'; t = std::thread(foo); std::cout << "after starting, joinable: " << t.joinable() << '\n'; t.join(); std::cout << "after joining, joinable: " << t.joinable() << '\n'; }
Output:
before starting, joinable: false after starting, joinable: true after joining, joinable: false
References
- C++20 standard (ISO/IEC 14882:2020):
- 32.4.2.5 Members [thread.thread.member]
- C++17 standard (ISO/IEC 14882:2017):
- 33.3.2.5 thread members [thread.thread.member]
- C++14 standard (ISO/IEC 14882:2014):
- 30.3.1.5 thread members [thread.thread.member]
- C++11 standard (ISO/IEC 14882:2011):
- 30.3.1.5 thread members [thread.thread.member]
See also
returns the id of the thread (public member function) |
|
waits for the thread to finish its execution (public member function) |
|
permits the thread to execute independently from the thread handle (public member function) |
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