C++ Concurrency (std::thread) Cheat Sheet

#include <thread>void task(int id) {    std::cout << "Thread " << id << " running\n";}std::thread t1(task, 1);                        // function + argsstd::thread t2([] { std::cout << "lambda\n"; }); // lambdastruct Functor {    void operator()() { std::cout << "functor\n"; }};std::thread t3(Functor{});t1.join();t2.join();t3.join();

void modify(int& value) { value *= 2; }int x = 10;// std::thread t(modify, x);         // ERROR: would copy x, function expects int&std::thread t(modify, std::ref(x));  // pass by reference explicitlyt.join();std::cout << x;   // 20// Move-only arguments must be moved instd::unique_ptr<int> p = std::make_unique<int>(5);std::thread t2([](std::unique_ptr<int> up) { std::cout << *up; }, std::move(p));t2.join();

std::thread worker(longRunningTask);worker.join();     // blocks the current thread until worker finishes// ORworker.detach();   // worker runs independently; caller no longer manages it                    // detached threads must not access destroyed local state// Both throw std::system_error if called on a thread that's not joinableif (worker.joinable()) {    worker.join();}// RAII wrapper to guarantee join on scope exit (avoids std::terminate)struct ThreadGuard {    std::thread& t;    ~ThreadGuard() { if (t.joinable()) t.join(); }};

std::cout << std::this_thread::get_id();unsigned n = std::thread::hardware_concurrency();  // approx # of hw threads, 0 if unknownstd::this_thread::sleep_for(std::chrono::milliseconds(100));thread_local int callCount = 0;   // separate instance per thread