What are some examples of condition variables in C++?

What are some examples of condition variables in C++?

Condition variables in C++ are used for synchronizing threads. They allow threads to wait until a particular condition is met.

Can you show me a simple code example?

Sure! Here's a basic 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 before proceeding.

What does the cv.wait function do?

The cv.wait function releases the mutex and puts the thread into a waiting state until it is notified. When notified, it re-acquires the mutex.

Are there any potential issues with using condition variables?

Yes, potential issues include deadlocks if not managed properly, and spurious wakeups where a thread wakes up without being notified.