链接列表追加最后一次不起作用

Question

为什么最后一次追加电话不起作用？我必须在这里添加一些垃圾，因为它抱怨我的帖子主要是代码，我希望它现在已经足够了。

typedef struct node {
    int val;
    struct node * next;
} node_t;

void append_node(node_t * head, int val) {
    node_t * current = head;

    while(current->next != NULL) {
        current = current->next;
    }

    current->next = malloc(sizeof(node_t));
    if(current->next == NULL)
    printf("err");

    current = current->next;
    current->val = val;
    current->next = NULL; //malloc(sizeof(node_t));
}

void print_list(node_t * head) {
    node_t * current = head;
    while(current->next != NULL) {
        printf("%d ", current->val);
        current = current->next;
    }
    printf("\n");
}

int main() {
    node_t * list = malloc(sizeof(node_t));
    list->val = 1;
    list->next = NULL;
    append_node(list,12);
    append_node(list,14);
    append_node(list,17);

    print_list(list);
    return 0;
}

输出：

1 12 14