Some C because I'm bored

So it was C programming day in IRC. I wrote a linked list:

#ifndef _LIST
#define _LIST
// List of things

#include 
#include 
#define null NULL
typedef struct Node Node;
typedef struct List List;
struct Node{
    // A node in the list
    Node* next;
    Node* prev;
    void* val;
};

struct List {
    // A list, has a front and an end
    // Maintains a pointer into the list
    Node* current;
    Node* front;
    Node* end;
    size_t size;
};

Node* append(List *list, void* val) {
    // Adds an element to the end of the list
    Node* new = malloc(sizeof(Node));
    list->end->prev->next = new;
    new->val = val;
    new->next = list->end;
    new->prev = list->end->prev;
    list->end->prev = new;
    list->size++;
    return new;
}

Node* preprend(List* list, void* val) {
    // Adds an element before the list
    Node* new = malloc(sizeof(Node));
    list->front->next->prev = new;
    new->val = val;
    new->prev = list->front;
    new->next = list->front->next;
    list->front->next = new;
    list->size++;
    return new;
}

Node* insert_after_current(List* list, void* val) {
    Node* new = malloc(sizeof(Node));
    new->val = val;
    new->next = list->current->next;
    new->prev = list->current;
    list->current->next->prev = new;
    list->current->next = new;
    return new;
}

List* delete_current(List* list) {
    // Removes the current node in the list
    Node* t1 = list->current->prev;
    Node* t2 = list->current->next;
    free(list->current);
    t1->next = t2;
    t2->prev = t1;
    list->size--;
    return list;
}

void* pop(List* list) {
    // Pops the element off the end of the list
    void* x = list->end->val;
    Node* temp = list->end->prev;
    free(list->end);
    list->end = temp;
    list->size--;
    return x;
}

Node* get_val(List* list) {
    // Returns the current node
    if(list->current->val == NULL)
        list->current = list->current->next;
    return list->current;
}

int is_front(List* list) {
    // Tests if current is at front of list
    return (list->current->prev == list->front);
}

int is_end(List* list) {
    // Tests if current is at end of list
    return (list->current->next == list->end);
}

Node* to_front(List* list) {
    // Set current to front of list
    return (list->current = list->front);
}

Node* to_end(List* list) {
    // For reverse iteration
    return (list->current = list->end);
}
Node* next(List* list) {
    // Increments pointer to next value in list
    // will not go off end of list
    if(list->current->next)
        list->current = list->current->next;
    return list->current;
}
Node* prev(List* list) {
    // Set pointer to previous value in list
    // will not go off end of list
    if(list->current->prev)
        list->current = list->current->prev;
    return list->current;
}

size_t count(List* list) {
    return list->size;
}

List* init_list() {
    List* list = malloc(sizeof(List));
    list->size = 0;
    list->front = malloc(sizeof(Node));
    list->end = malloc(sizeof(Node));
    int x = 0;
    list->front->val = list->end->val = NULL;
    list->front->prev = NULL;
    list->front->next = list->end;
    list->end->next = NULL;
    list->end->prev = list->front;
    list->current = list->front;
    return list;
}

#endif

And here is the code to use it:

#include "list.c"
#include 
#include 
int main() {
    List* l = init_list();
    int nums[] = {1,2,3,4,5,5,6};
    int i;
    for(i = 0;i < 7;i++) {
        printf("Adding to list: %d\n",nums[i]);
        append(l,(void*) &(nums[i]));
    }
    printf("List size: %d\n",count(l));
    while(!is_end(l)) {
        next(l);
        printf("%d\n",*(int*)(get_val(l)->val));
    }
    return 0;
}