efficient thread-safe singleton in C++

Question

The usual pattern for a singleton class is something like

static Foo &getInst()
{
  static Foo *inst = NULL;
  if(inst == NULL)
    inst = new Foo(...);
         


        

Answer 1

Use pthread_once, which is guaranteed that the initialization function is run once atomically.

(On Mac OS X it uses a spin lock. Don't know the implementation of other platforms.)