How do I use std::lock in C++?

Can you explain how to use std::lock in C++?

Sure! std::lock is used to lock multiple mutexes at once to avoid deadlocks. You can pass the mutexes as arguments.

What happens if I try to lock a mutex that is already locked?

If you try to lock a mutex that is already locked by the same thread, it will cause a deadlock. std::lock helps prevent this.

Can you show me a simple code example?

Of course! Here's a basic example:

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

std::mutex m1, m2;

void func1() {
    std::lock(m1, m2);
    std::lock_guard<std::mutex> lg1(m1, std::adopt_lock);
    std::lock_guard<std::mutex> lg2(m2, std::adopt_lock);
    // critical section
}

void func2() {
    std::lock(m1, m2);
    std::lock_guard<std::mutex> lg1(m1, std::adopt_lock);
    std::lock_guard<std::mutex> lg2(m2, std::adopt_lock);
    // critical section
}

Are there any performance considerations I should be aware of?

Yes, locking can introduce overhead. It's best to minimize the time spent in locked sections and avoid locking too many mutexes at once.