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Free

Recall the refcount_free function that you wrote in the previous chapter. It should have looked something like this:

void refcount_free(snek_object_t *obj) {
  switch (obj->kind) {
    case INTEGER:
    case FLOAT:
      break;
    case STRING:
      free(obj->data.v_string);
      break;
    case VECTOR3: {
      snek_vector_t vec = obj->data.v_vector3;
      refcount_dec(vec.x);
      refcount_dec(vec.y);
      refcount_dec(vec.z);
      break;
    }
    case ARRAY: {
      snek_array_t *array = &obj->data.v_array;
      for (size_t i = 0; i < array->size; i++) {
        refcount_dec(array->elements[i]);
      }
      free(array->elements);
      break;
    }
  }
  free(obj);
}

Assignment

Let's rewrite our free-ing logic for mark-and-sweep. Because the virtual machine is the one tracking objects, all of the refcount_dec work can be removed! There's some very cool tricks coming up for mark-and-sweep to manage this, but for now you can just trust me that we'll correctly free any of the contained elements if they are no longer alive.

In snekobject.c complete the snek_object_free function.
1. INTEGER, FLOAT, and STRING objects should all work the same as the refcount version (non container types).
2. VECTOR3 doesn't need to do anything before freeing the object, because the mark-and-sweep will handle the contained objects.
3. ARRAY should free the elements array, but not the objects themselves because the mark-and-sweep will handle that.
In vm.c complete the vm_free function.
1. Iterate over all the VM's frames and free them using frame_free.
2. Free the frames stack itself using stack_free.
3. Iterate over all the VM's objects and free them using snek_object_free.
4. Free the objects stack itself using stack_free.
5. Free the VM struct itself.