Question

以下功能有什么问题吗？不知何故，他们正在创建一个段错误。

struct processNode* create_node()
{
    struct processNode* newNode =  (struct processNode*)malloc(sizeof(struct processNode));
    newNode->next = NULL;
    return newNode;
}

struct processNode* append_node(struct processNode* list,struct processNode* newNode )
{
    struct processNode* tracker= NULL;
    tracker = list;

    if(tracker == NULL)
    {
        tracker = newNode;
    }
    else
    {
        while(tracker->next != NULL)
        {
            tracker =tracker->next;
        }
        tracker->next = newNode;
        tracker = tracker->next;
    }

    tracker->next=NULL;
    tracker = list;
    return tracker;
}

我在C中创建一个shell，需要创建一个链接列表来解析用户的命令行。在第二个函数中，我打算返回一个带有新附加指针的新列表;

Answer 1

我想函数应该返回一个指向列表头部的指针。

假设在list为NULL

的情况下调用该函数

所以这很好：

    if(tracker == NULL)
    {
      tracker = newNode;
    }

但是这里

    tracker = list;   <---- Not good....
    return tracker;

您覆盖跟踪器并返回NULL

您可以尝试：

struct processNode* append_node(struct processNode* list,struct processNode* newNode )
{
    struct processNode* tracker= NULL;
    tracker = list;

    if(tracker == NULL)
    {
        tracker = newNode;
        return tracker;        // Notice
    }

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

    return list; 
}

Answer 2

以下情况会在tracker->next=NULL;行

上给出seg错误

tracker != NULL && newNode == NULL

tracker == NULL

    ....
tracker = tracker->next;
}

//THE FOLLOWING LINE WILL CAUSE PROBLEM
tracker->next=NULL; 
tracker = list;
return tracker;
 ....
}

你可以这样做：

struct processNode* append_node(struct processNode* list,struct processNode* newNode )
{
    struct processNode* tracker= NULL;
    tracker = list;

     if(!newNode){
        //Do nothing 
     }          
    else if(tracker == NULL)
    {
        tracker = newNode;
    }
    else
    {
        while(tracker->next != NULL)
        {
            tracker = tracker->next;
        }
        tracker->next = newNode;
        tracker = tracker->next;
    }

    return tracker;
}

调试以下功能（段故障错误）

2 个答案: