int make_post(const User *author, User *target, char *contents) {
        if (author == NULL || target == NULL){
                return 2;
        } else if (already_friends((User *) author, (User *) target) != 0) {
                return 1;
        } else {
                time_t *t;
                time(t);
                if (target->first_post == NULL) {
                        target->first_post = malloc(sizeof(Post));
                        strcpy((target->first_post)->author, author->name);
                        strcpy((target->first_post)->contents, contents);
                        (target->first_post)->date = t;
                        (target->first_post)->next = NULL;
                } else {
                        Post *new_post = malloc(sizeof(Post));
                        strcpy(new_post->author, author->name);
                        strcpy(new_post->contents, contents);
                        new_post->date = t;
                        new_post->next = target->first_post;
                        target->first_post = new_post;
                }
                return 0;
        }
}

Add a new post to the start of the linked list target->first_post with contents contents and a pointer to current time.