c - 取消引用 NULL 指针 'head' ,'tail

Question

我用链表制作了一个蛇程序，该程序正在运行，但我有一些警告，我想知道我是否做错了什么，或者只是忽略了一些东西。程序本身运行没有任何错误。

我

//Thats what I send from main

SNAKE* snake = (SNAKE*)malloc(sizeof(SNAKE));





//Thats the function
void initialSnaKE(SNAKE* snake){
    NODE* tail = (NODE*)(malloc(sizeof(NODE)));
    NODE* head = (NODE*)(malloc(sizeof(NODE)));
    head->prev = NULL;
    tail->prev = head;
    head->next = tail;
    tail->next = NULL;
    head->x = ROWS / 2;
    head->y = COLS / 2;
    snake->head = head;
    snake->tail = tail;
}

Answer 1

malloc 可能会失败，这就是编译器所提示的。在取消引用指针之前，您必须进行适当的 NULL 检查。

void initialSnaKE(SNAKE* snake){

    if (!snake) return; //invalid input

    NODE* tail = (NODE*)(malloc(sizeof(NODE)));
    if (!tail) return; //allocation failed.

    NODE* head = (NODE*)(malloc(sizeof(NODE)));
    if (!head) {
       free(tail);
       return;
     }


    head->prev = NULL;
    tail->prev = head;
    head->next = tail;
    tail->next = NULL;
    head->x = ROWS / 2;
    head->y = COLS / 2;
    snake->head = head;
    snake->tail = tail;
}