How to std::mutex::lock until function returns

Question

I want to return a std::vector. This std::vector may be accessed from other threads (read and write). How can I unlock my std::mutex just

Answer 1

Use a std::lock_guard to handle locking and unlocking the mutex via RAII, that is literally what it was made for.

int foo()
{
    std::lock_guard lg(some_mutex);  // This now locked your mutex
    for (auto& element : some_vector)
    {
        // do vector stuff
    }
    return 5;
}  // lg falls out of scope, some_mutex gets unlocked

After foo returns, lg will fall out of scope, and unlock some_mutex when it does.