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

using namespace std ;

mutex myMutex ;

void protectedFunction()
{
    lock_guard<mutex> lock(myMutex) ; // Locks myMutex
    cout << "Inside protected function." << endl;
    lock_guard<mutex> lock1 = lock  ;
    // ... critical section code ...
} // myMutex is automatically unlocked when 'lock' goes out of scope

void anotherFunction( lock_guard<mutex> lockGuardObject )
{

}

int main()
{
    lock_guard<mutex> lock1(myMutex); // Locks myMutex
    cout << "Lock1 acquired." << endl;
    anotherFunction( lock1 ) ;
    // The following line would result in a compilation error:
    // lock_guard<mutex> lock2 = lock1; // ERROR: Cannot copy lock_guard

    // You also cannot pass a lock_guard by value to a function:
    // void anotherFunction(lock_guard<mutex> l) {}
    // anotherFunction(lock1); // ERROR: Cannot copy lock_guard

    thread t1(protectedFunction);
    t1.join();

    cout << "Lock1 released." << endl; // lock1 goes out of scope here
    return 0;
}