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

What is std::lock and how do I use it in my C++ code?

std::lock is a function that locks multiple mutexes to prevent deadlocks. You can use it by passing the mutexes you want to lock.

Can you show me a simple example of using std::lock?

Sure! 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
}

What happens if I try to lock the same mutex twice?

If you try to lock the same mutex twice from the same thread, it will cause a deadlock. Always ensure that each mutex is locked only once per thread.

Are there any performance considerations when using std::lock?

Yes, using std::lock can introduce overhead due to the locking mechanism. It's important to minimize the time spent in critical sections to improve performance.