c - 无法将第二个元素插入链表 |指向函数的指针被损坏

Question

下面是相关代码:

typedef struct Node_t {
    ListElement data;
    struct Node_t* next;
} Node;

struct List_t {
    Node* head;
    Node* tail;
    Node* current;
    int size;
    CopyListElement copyF;
    FreeListElement freeF;
};

<小时/>

static ListResult initializeNode(List list, ListElement element, Node* newNode){
    printf("\nEntered initializeNode\n");
    if ((list == NULL) || (element == NULL)) return LIST_NULL_ARGUMENT;
    newNode = malloc(sizeof(Node));
    if (newNode == NULL) return LIST_OUT_OF_MEMORY;
    printf("\nWithin initializeNode, before copyF\n");
    ListElement newElement = list->copyF(element);
    printf("\nWithin initializeNode, after copyF\n");
    if (newElement == NULL) return LIST_OUT_OF_MEMORY;
    newNode->data = newElement;
    printf("\nLast line within initializeNode\n");
    return LIST_SUCCESS;
}

<小时/>

List listCreate(CopyListElement copyElement, FreeListElement freeElement){

    //Check if there is a NULL argument.
    if ((copyElement == NULL) || (freeElement == NULL)) return NULL;

    //Check wether there is enough memory.
    List newList = malloc(sizeof(List));
    if (newList == NULL) return NULL;
    //Initialize an empty List.
    newList->head = NULL;
    newList->tail = NULL;
    newList->size = 0;
    newList->current = NULL;
    newList->copyF = copyElement;
    newList->freeF = freeElement;

    return newList;
}

<小时/>

ListResult listInsertFirst(List list, ListElement element){
    printf("\nEntered listInsertFirst\n");
    Node* newNode;
    ListResult result = initializeNode(list, element, newNode);
    printf("\n Node was initialized\n");
    if (result != LIST_SUCCESS) {
        return result;
    }

    printf("\nEntering logistic works within listInsertFirst\n");
    //Finish logistic work within the Node.
    newNode->next = list->head;
    list->head = newNode;
    list->size++;
    printf("\nElement was inserted successfully\n");

printf("\nCheck list->CopyF within listInsertFirst\n");
list->copyF(element);
printf("\nCheck list->CopyF within listInsertFirst: PASSED\n");

    return LIST_SUCCESS;
}

<小时/>

在主函数中我正在尝试:

List list = listCreate(&copyInt, &freeInt);

ListResult result;
int el=2;
//ListElement e1;
//ListElement e2;

result = listInsertFirst(list,&el);
printf("\nresult = %d\n", result);

result = listInsertFirst(list,&el);
printf("\nresult = %d\n", result);

<小时/>

After compiling and running I get:

Entered listInsertFirst

Entered initializeNode

Within initializeNode, before copyF

Within initializeNode, after copyF

Last line within initializeNode

Node was initialized

Entering logistic works within listInsertFirst

Element was inserted successfully

Check list->CopyF within listInsertFirst Segmentation fault: 11

由于某种原因，[指向函数] list->copyF 的指针被损坏了[我认为]。

Answer 1

根据标签，我假设这是 C 代码，而不是 C++。鉴于您混合了数据定义和实际代码语句，我不希望它在 C 中工作，我不能 100% 确定它是真正的 C，在这种情况下，我可能对下面的错误是错误的。

首先，initializeNode() 的接口(interface)并不符合您的预期。您可能想要:

static ListResult initializeNode(List list, ListElement element, Node** newNodep)
{
    Node *newNode = malloc(sizeof(Node));
    if (newNode == NULL) return LIST_OUT_OF_MEMORY;
    ListElement newElement = list->copyF(element);
    if (newElement == NULL) return LIST_OUT_OF_MEMORY;
    newNode->data = newElement;
    *newNodep = newNode;
    return LIST_SUCCESS;
}

这样您创建的节点就会被传回。

我不知道 CopyInt() 的作用，但如果它确实是函数遇到总线错误，那么 initializeNode() 的错误就不是您的问题。但是，在报告崩溃之前您可能看不到所有 printf 的输出。

如果 CopyInt() 执行我所期望的操作，它会执行以下操作:

ListElement CopyInt(int *val)
{
    ListElement *e = malloc(sizeof(ListElement));
    if (e) 
        e->val = *val;
    return e;
}

这里出现第二次总线错误的唯一方法是，如果您弄乱了库函数 malloc() 维护的数据结构。不幸的是，对于这个理论，我没有看到任何比内存泄漏更糟糕的事情。