static lock_guard with static mutex too?

Question

So I've some thread-unsafe function call which I need to make thread safe so I'm trying to use a std::mutex and a std::lock_guard. Currently code looks like this -

int myFunc(int value){
    static std::mutex m;
    std::lock_guard lock(m);
    auto a = unsafe_call(value);
    return a;
}

the unsafe_call() being the thread-unsafe function. I've also put static around the mutex because then the function will have different mutexes for each separate call.

What I want to know is, should I also make lock_guard static because the mutex is static one, as I was told by some coworker of mine. I don't see a reason why should I do this, because I consider lock_guard to be a simple .lock() and .unlock() call, but the suggestion from coworker is confusing me.

Answer 1

should I also make lock_guard static because the mutex is static one, as I was told by some coworker of mine.

Your coworker is completely wrong, lock_guard is using RAII mechanism to control resource (mutex in this case) and making it static would completely defeat it's purpose - mutex would be locked once on the first execution of the function and released only when program terminates, ie effectively you would not be using mutex at all.