What is std::condition_variable in C++?

Can you explain what std::condition_variable is in C++?

Sure! std::condition_variable is a synchronization primitive that allows threads to wait until a particular condition is met.

How does it work with mutexes?

It works in conjunction with std::mutex. A thread can lock a mutex and then wait on a condition variable, releasing the mutex while waiting.

Can you give me a simple code example?

Certainly! Here's a basic example:

#include <iostream>
#include <thread>
#include <condition_variable>
#include <mutex>

std::condition_variable cv;
std::mutex m;
bool ready = false;

void worker() {
    std::unique_lock<std::mutex> lock(m);
    cv.wait(lock, [] { return ready; });
    std::cout << "Worker thread proceeding..." << std::endl;
}

int main() {
    std::thread t(worker);
    {
        std::lock_guard<std::mutex> lock(m);
        ready = true;
    }
    cv.notify_one();
    t.join();
    return 0;
}

What are some common use cases for condition variables?

Common use cases include producer-consumer scenarios, where one thread produces data and another consumes it, waiting for data to be available.