GLib-2.0 ▶ GLib ▶ once_init_enterSince 2.14

Function to be called when starting a critical initialization section. The argument location must point to a static 0-initialized variable that will be set to a value other than 0 at the end of the initialization section. In combination with g_once_init_leave() and the unique address value_location, it can be ensured that an initialization section will be executed only once during a program's life time, and that concurrent threads are blocked until initialization completed. To be used in constructs like this:

  static gsize initialization_value = 0;

  if (g_once_init_enter (&initialization_value))
    {
      gsize setup_value = 42; // initialization code here

      g_once_init_leave (&initialization_value, setup_value);
    }

  // use initialization_value here
Copy

While location has a volatile qualifier, this is a historical artifact and the pointer passed to it should not be volatile.