What is a condition variable in C++?

Can you explain what a condition variable is in C++?

Sure! A condition variable in C++ is a synchronization primitive that allows threads to wait until a particular condition occurs.

How do I use condition variables in my code?

You typically use condition variables with a mutex. You lock the mutex, check the condition, and if it's not met, you call wait on the condition variable.

Can you give me a code example?

Certainly! Here's a simple example:

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

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

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

int main() {
    std::thread t(worker);
    std::this_thread::sleep_for(std::chrono::seconds(1));
    {
        std::lock_guard<std::mutex> lock(mtx);
        ready = true;
    }
    cv.notify_one();
    t.join();
    return 0;
}

This code demonstrates a worker thread waiting for a condition to be met.

What happens if I forget to notify the condition variable?

If you forget to notify the condition variable, the waiting thread will remain blocked indefinitely, which can lead to deadlocks.