结构和链表(C)

Question

我正在尝试实现一个链表来保存历史信息。

节点结构的定义如下:

struct HistoryNode {
    int Value;
    struct HistoryNode *Last, *Next;
};

我还创建了另一个结构来包含指向列表中头/尾/当前节点的指针:

struct _History {
    struct HistoryNode *Head, *Tail, *Current;
} History = {
    NULL, NULL, NULL,
};

最后，我创建了一个函数来将一个节点添加到列表中:

void AddHistory(void) {
    struct HistoryNode *NewNode;
    //Allocate new node memory
    NewNode = malloc(sizeof(NewNode));
    if(NewNode == NULL) {
        Die("malloc(%d) failed", sizeof(NewNode));
    }
    //Re-arrange pointers in new node and head/tail/current
    if(History.Current == NULL) {
        NewNode->Next = NULL;
        NewNode->Last = NULL;
        History.Current = NewNode;
        History.Head = NewNode;
        History.Tail = NewNode;
    } else {
        NewNode->Next = NULL;
        NewNode->Last = History.Current;
        History.Current = NewNode;
        History.Tail = NewNode;
    }
}

GCC将此错误连同几个错误一起返回:

Scribe.c: In function 'AddHistory':
Scribe.c:509:15: error: request for member 'Current' in something not a structure or union
Scribe.c:513:16: error: request for member 'Current' in something not a structure or union
Scribe.c:514:16: error: request for member 'Head' in something not a structure or union
Scribe.c:515:16: error: request for member 'Tail' in something not a structure or union
Scribe.c:518:32: error: request for member 'Current' in something not a structure or union
Scribe.c:520:16: error: request for member 'Current' in something not a structure or union
Scribe.c:521:16: error: request for member 'Tail' in something not a structure or union

我不知道为什么会发生这种情况，有什么帮助吗?

谢谢,——亚历克斯

Answer 1

如果将History声明为全局变量，则编译成功，如http://cfiddle.net/LwucyB所示。关于该问题的另一个注意事项与NewNode的分配有关，应如下所示

NewNode = malloc(sizeof(struct HistoryNode));

你需要为结构体分配空间，而不仅仅是指针。

Answer 2

您需要malloc sizeof(HistoryNode)，而不是NewNode(它是一个指向HistoryNode的指针)