Tag Archive for magic static

Implementing a Thread-Safe Singleton with C++11 Using Magic Statics

10 Aug, 2017  5 Comments

A couple of years ago I wrote a blogpost on how to write a thread-safe singleton using C++11. That implementation used std::call_once().

However, if your compiler is fully C++11 compliant, and by now, all major compilers are fully compliant, then the best way to implement a singleton is to use a magic static, as follows:

class CSingleton final
{
public:
	static CSingleton& GetInstance();

private:
	CSingleton() = default;
	~CSingleton() = default;

	CSingleton(const CSingleton&) = delete;
	CSingleton& operator=(const CSingleton&) = delete;
	CSingleton(CSingleton&&) = delete;
	CSingleton& operator=(CSingleton&&) = delete;
};

CSingleton& CSingleton::GetInstance()
{
	static CSingleton instance;
	return instance;
}

The most important change is the implementation of GetInstance() which now contains a local static variable (magic static). C++11 guarantees that this will be initialized in a thread-safe way.
I have now also marked the class as final, made the destructor non-virtual and private, and deleted the move constructor and move assignment operator.

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