Re: The singleton design pattern in D, C++ and Java

[Max Samukha]

On 16.07.2010 16:49, dsimcha wrote:

D makes it very easy to create an efficient thread-safe Singleton 
implementation,
using a method that was inspired by broken double-checked locking, but uses
thread-local storage to be correct.  The following algorithm guarantees that the
synchronized block guarding the Singleton will be entered at most once per 
thread
throughout the lifetime of the program.  I invented it myself, but it's fairly
simple and might have been independently invented elsewhere:

class Singleton {
private:
     static bool initialized;  // Thread-local
     __gshared static Singleton instance;

     this() {}

public:

     static Singleton getInstance() {
         if(initialized) {
             return instance;
         }

         synchronized(Singleton.classinfo) {
             scope(success) initialized = true;
             if(instance !is null) {
                 return instance;
             }

             instance = new Singleton;
             return instance;
        }
     }
}

I invented it here:

http://www.digitalmars.com/d/archives/digitalmars/D/Static_constructors_in_circularly_imported_modules_-_again_110518.html#N110527

Which proves we are great minds :)