c - 访问冲突读取位置 0xCDCDCDCD

Question

如标题所述，我遇到了一个错误

Access violation reading location 0xCDCDCDCD.

现在我正在处理一个链表数组，我相信麻烦在于向链表中添加一些东西。我通常对此没有意见，但我觉得我在内存分配方面做错了什么。

这是我的结构:

图表:

typedef struct graph
{
    int V;
    int *state;
    EdgeList *edges;
} Graph;

边缘:

typedef struct edge
{
    int toVertex;
    int weight;
} Edge;

边缘列表:

typedef struct edgeNode
{
    Edge edge;
    struct edgeNode *next;
} *EdgeList;

这是运行它的主要函数:

main()
{
    Graph myGraph;
    scanf("%d", &(myGraph.V));
    myGraph.state = (int)malloc(myGraph.V*sizeof(int));
    myGraph.edges = (EdgeList*)malloc(myGraph.V*sizeof(EdgeList));
    int *inDegrees;
    inDegrees = (int)malloc(sizeof(int)*myGraph.V);

    /*  Sets all array values to 0  */
    for (int counter = 0; counter < myGraph.V; counter++)
    {
        inDegrees[counter] = 0;
    }


    for (int i = 0; i < myGraph.V; i++)
    {
        int number_of_edges;
        int input = 0;  /*For that little experimental bit*/
        scanf("%d", &(myGraph.state[i]));
        scanf("%d", &number_of_edges);
        if (number_of_edges > 0)
        {
            for (int j = 0; j < number_of_edges; j++)
            {
                Edge newEdge;
                scanf("%d,%d", &(newEdge.toVertex), &(newEdge.weight));
                inDegrees[newEdge.toVertex]++;
                printf("%s%d\n", "\nOoh, new input for ", newEdge.toVertex);

                /*insert at front*/
                EdgeList newNode = (EdgeList)malloc(sizeof (struct edgeNode));
                newNode->edge = newEdge;

                newNode->next = myGraph.edges[i];
                myGraph.edges[i] = newNode;


                /* Bit to calculate state.*/

                EdgeList current = myGraph.edges[i];

                while (current != NULL)
                {
                    if (current->edge.toVertex == i)
                    {
                        input += (current->edge.weight)*(myGraph.state[i]);
                    }
                    current = current->next;
                }
            }
            if (input > 0)
            {
                myGraph.state[i] = 1;
            }
            else
            {
                myGraph.state[i] = 0;
            }
        }
    }

    //print
    for (int k = 0; k < myGraph.V; k++)
    {
        printf("\n%s%d%s", "In degrees for ", k, ": ");
        printf("%d", inDegrees[k]);
    }

}

特别是在遍历链表的过程中出现错误。它在上面的代码中，但我会在这里突出显示它:

EdgeList current = myGraph.edges[i];

while (current != NULL)
{
    if (current->edge.toVertex == i)
    {
        input += (current->edge.weight)*(myGraph.state[i]);
    }
    current = current->next;
}

如果有人能提供帮助，我将不胜感激，因为我被困住了。

Answer 1

1. 在newNode->next = myGraph.edges[i] 中将通过malloc() 分配的未初始化缓冲区中的值分配给newNode->edge； 。
2. newNode 通过 myGraph.edges[i] = newNode; 和 EdgeList current = myGraph.edges 设置为 current [i];.
3. 假设 malloc() 成功，current 在这里不为 NULL，因此进入循环。
4. 在current = current->next;中将1中赋值的未初始​​化值赋值给current。
5. 通过使用通过 malloc() 分配的缓冲区中的值来调用未定义的行为，并且在 current != NULL 未初始化。

要修复此错误，请初始化 myGraph.edges，例如，以这种方式:

myGraph.edges = (EdgeList*)malloc(myGraph.V*sizeof(EdgeList));
for (int i = 0; i < myGraph.V; i++)
{
    myGraph.edges[i] = NULL;
}

此外，删除对从 malloc() 返回的指针的 int 的有害转换。将返回值显式转换为指针也是 not considered as good .