std::thread::thread

 

C++

Language

Concepts

Utilities library

Strings library

Containers library

Algorithms library

Iterators library

Numerics library

Input/output library

Localizations library

Regular expressions library (C++11)

Atomic operations library (C++11)

Thread support library (C++11)

 

Thread support library

Threads
thread (C++11)
this_thread namespace
get_id (C++11) yield (C++11)	sleep_for (C++11) sleep_until (C++11)
Mutual exclusion
mutex (C++11) timed_mutex (C++11)	recursive_mutex (C++11) recursive_timed_mutex (C++11)
Generic lock management
lock_guard (C++11) unique_lock (C++11) defer_lock_t try_to_lock_t adopt_lock_t (C++11) (C++11) (C++11)	lock (C++11) try_lock (C++11) defer_lock try_to_lock adopt_lock (C++11) (C++11) (C++11)
Condition variables
condition_variable (C++11)
condition_variable_any (C++11)
notify_all_at_thread_exit (C++11)
cv_status (C++11)
Futures
promise (C++11) future (C++11) shared_future (C++11) packaged_task (C++11) async (C++11)	launch (C++11) future_status (C++11) future_error (C++11) future_category (C++11) future_errc (C++11)

 

std::thread

Member classes

thread::id

Member functions

thread::thread

thread::~thread

thread::operator=

Observers

thread::joinable

thread::get_id

thread::native_handle

thread::hardware_concurrency

Operations

thread::join

thread::detach

thread::swap

Non-member functions

std::swap

 

thread();	(1)	(since C++11)
thread( thread&& other );	(2)	(since C++11)
template< class Function, class... Args > explicit thread( Function&& f, Args&&... args );	(3)	(since C++11)
thread(const thread&) = delete;	(4)	(since C++11)

Constructs new thread object.

1) Creates new thread object which does not represent a thread.

2) Move constructor. Constructs the thread object to represent the thread of execution that was represented by other. After this call other no longer represents a thread of execution.

3) Creates new std::thread object and associates it with a thread of execution. First copies all arguments args... to thread-local storage as if by the function template <class T>
typename decay<T>::type decay_copy(T&& v) {
    return std::forward<T>(v);
} and then executes the given function f as f(copied_args...) on the new thread of execution, where copied_args are the results of calling decay_copy as defined above. Any exceptions during evaluation and copying of the arguments are thrown in the current thread, not the new thread.

4) The copy constructor is deleted; threads are not copyable. No two std::thread objects may represent the same thread of execution.

Parameters

other	-	another thread object to construct this thread object with
f	-	function to execute in the new thread
args...	-	arguments to pass to the new function

Exceptions

1-2)

noexcept specification:  

noexcept

  (since C++11)

3) std::system_error if the thread could not be started. The exception may represent the error condition std::errc::resource_unavailable_try_again or another implementation-specific error condition.

Notes

The arguments to the thread function are copied by value. If a reference argument needs to be passed to the thread function, it has to be wrapped, e.g. with std::ref or std::cref

Any return value from the function is ignored. If the function throws an exception, std::terminate() is called. In order to pass return values or exceptions back to the calling thread, std::promise or std::async may be used.

Example

#include <iostream>
#include <utility>
#include <thread>
#include <chrono>
#include <functional>
#include <atomic>
 
void f1(int n)
{
    for(int i=0; i<5; ++i) {
        std::cout << "Thread " << n << " executing\n";
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }
}
 
void f2(int& n)
{
    for(int i=0; i<5; ++i) {
        std::cout << "Thread 2 executing\n";
        ++n;
        std::this_thread::sleep_for(std::chrono::milliseconds(10));
    }
}
 
int main()
{
    int n = 0;
    std::thread t1; // t1 is not a thread
    std::thread t2(f1, n+1); // pass by value
    std::thread t3(f2, std::ref(n)); // pass by reference
    std::thread t4(std::move(t3)); // t4 is now running f2(). t3 is no longer a thread
    t2.join();
    t4.join();
    std::cout << "Final value of n is " << n << '\n';
}

Output:

Thread 1 executing
Thread 2 executing
Thread 1 executing
Thread 2 executing
Thread 1 executing
Thread 2 executing
Thread 1 executing
Thread 2 executing
Thread 1 executing
Thread 2 executing
Final value of n is 5