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 :)