Memory-managed wrapper type.

Construct a Once struct initialized to zero.

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 onceInitLeave and the unique address valueLocation, 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:

C code

 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

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

Since: 2.14

Counterpart to onceInitEnter. Expects a location of a static 0-initialized initialization variable, and an initialization value other than 0. Sets the variable to the initialization value, and releases concurrent threads blocking in onceInitEnter on this initialization variable.

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

Since: 2.14

Set the value of the “retval” field to Nothing. When overloading is enabled, this is equivalent to

clear #retval

Get the value of the “retval” field. When overloading is enabled, this is equivalent to

get once #retval

Set the value of the “retval” field. When overloading is enabled, this is equivalent to

set once [ #retval := value ]

Get the value of the “status” field. When overloading is enabled, this is equivalent to

get once #status

Set the value of the “status” field. When overloading is enabled, this is equivalent to

set once [ #status := value ]