It says 'dataIn was nullptr'.

QUEUE* Node = createQueue();

int* dataIn;

int* dataOut;

void BreadthFirstprint(Tree* tree) {


    if (tree) {
        *dataIn = tree->data;
        enqueue(Node, &dataIn);
        BreadthFirstprint(tree->left);
        BreadthFirstprint(tree->right);
    }
    while (!emptyQueue(Node))
    {
        dequeue(Node, (void**)&dataOut);
        printf("[ %d ] ", *dataOut);
    }}