Apply stub

A procedure corresponding to a particular method that accepts as arguments: the object on which the method is to be invoked, a pointer to a location in memory where the method's result should be stored, a pointer to the method's procedure, and the method's arguments in the form of a va_list. The apply stub extracts the arguments from the va_list, invokes the method with its arguments, and stores its result in the specified location. Apply stubs are registered with class objects when instance methods are defined, and are invoked using the somApply function. Typically, implementations that override somDispatch call somApply to invoke a method on a va_list of arguments.