Iterating over doubly linked lists

main.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

typedef struct Node {
    int x;
    struct Node* next;
    struct Node* prev;
} Node;

int main(int argc, char* argv[]) {
    Node* tail = malloc(sizeof(Node));
    if (tail == NULL) {
        return 1;
    }
    tail->x = 1;
    tail->prev = NULL;
    tail->next = malloc(sizeof(Node));
    if (tail->next == NULL) {
        return 2;
    }
    
    tail->next->x = 3;
    tail->next->prev = tail;
    tail->next->next = malloc(sizeof(Node));
    if (tail->next->next == NULL) {
        return 3;
    }

    tail->next->next->x = 7;
    tail->next->next->prev = tail->next;
    tail->next->next->next = NULL;
    
    Node* head = tail->next->next;
    
    // Forward
    for (Node* curr = tail; curr != NULL; curr = curr->next) {
        printf("%d ", curr->x);
    }
    
    // Backwards
    for (Node* curr = head; curr != NULL; curr = curr->prev) {
        printf("%d ", curr->x);
    }

    return 0;
}