Threads_basics

Thread Basics

C++11 introduced native threading support. This chapter covers how to create and manage threads in C++.

Creating Threads

#include <thread>
#include <iostream>

void hello() {
    std::cout << "Hello from thread!\n";
}

int main() {
    std::thread t(hello);  // Create thread running hello()
    t.join();  // Wait for thread to complete

    std::cout << "Main thread continues\n";
    return 0;
}

Passing Arguments to Threads

#include <thread>
#include <iostream>

void print(int x, const std::string& msg) {
    std::cout << msg << ": " << x << "\n";
}

int main() {
    // Arguments are copied by default
    std::thread t1(print, 42, "Answer");

    // Use std::ref for references
    int value = 100;
    std::thread t2(print, value, "Value");  // Copies value

    t1.join();
    t2.join();

    return 0;
}

Thread Management

#include <thread>

void worker() {}

int main() {
    std::thread t(worker);

    // Join - wait for thread to finish
    t.join();

    // Detach - let thread run independently
    std::thread t2(worker);
    t2.detach();  // Now runs in background

    // Check if joinable
    if (t.joinable()) { t.join(); }

    return 0;
}

Lambda Threads

int main() {
    int counter = 0;

    std::thread t([&counter]() {
        for (int i = 0; i < 1000; i++) {
            counter++;
        }
    });

    t.join();
    std::cout << "Counter: " << counter << "\n";

    return 0;
}

Thread ID

#include <thread>
#include <iostream>

int main() {
    std::thread t([]() {});

    std::cout << "Main thread ID: " << std::this_thread::get_id() << "\n";
    std::cout << "Worker thread ID: " << t.get_id() << "\n";

    t.join();
    return 0;
}

Key Takeaways

• Use std::thread to create concurrent execution
• Always join() or detach() threads before destruction
• Use lambdas with captures for complex thread functions
• Thread arguments are copied by default

Next Steps

Let’s learn about mutexes for thread synchronization.

Next Chapter: 36_mutex_locks.md - Mutexes and Locking