Effective C++ 14. Think carefully about copying behavior in resource-managing classes

class Mutex {

};

void lock(Mutex *pm);
void unlock(Mutex *mp);

class Lock {
public:
    explicit Lock(Mutex *pm): mutexPtr(pm) {
        lock (mutexPtr);
    }
    ~Lock() {
        unlock (mutexPtr);
    }
private:
    Mutex *mutexPtr;
};

Mutex m;
Lock ml1(&m);
Lock ml2(ml1); // point to same object

I. Prohibit copying

class Uncopyable {
private:
Uncopyable(const Uncopyable&);
Uncopyable& operator=(const Uncopyable&);

class Lock: private Uncopyable {
};

II. Reference-count the underlying resource

tr1::shared_ptr allows specification of a “deleter” - a function or function object to be called when the reference count goes to zero.

class Lock {
public:
    explicit Lock(Mutex *pm): mutexPtr(pm, unlock) {
        lock(mutexPtr.get());
    }
private:
    std::tr1::shared_ptr<Mutex> multexPtr;
};