当我在链表中插入任何值之前选择删除选项时，出现分段错误

Question

#include<stdio.h>
#include<malloc.h>

typedef struct nnode
{
    int value;
    struct nnode *next;

} node;

void insert(node **ptr, int val) //for insertion
{
    node *temp, *temp2;
    temp = *ptr;
    if (*ptr == NULL)//if list is empty
  {
        temp = (node *) malloc(sizeof (node));
        temp->value = val;
        temp->next = NULL;
        *ptr = temp;
  }       
        else 
     {
        while (temp->next != NULL)     
        {
            temp = temp->next;
        }
        temp2 = (node *) malloc(sizeof (node));
        temp2->value = val;
        temp2->next = NULL;
        temp->next = temp2;
     }
}

void display_node(node **ptr)
{
    node *temp;
    temp = *ptr;
    while (temp != NULL) 
   {
    printf("%d--->", temp->value);
    temp = temp->next;
   }
    printf("null");
}

void de_node(node **ptr)
{
    int val;

    node *temp, *temp2;
    temp = *ptr;
    temp2 = temp->next;
    printf("\nenter the value to be deleted\n");
    scanf("%d", &val);
    if ((*ptr) == NULL)
     {
        printf("list is empty .....");
        return;
     } 
    else if ((*ptr)->value == val)
     {

        *ptr = (*ptr)->next;
        free(temp);

     } 
     else 
       {
     while ((temp->next->value != val)&&(temp2->next != NULL))
         {
            temp = temp->next;
            temp2 = temp->next;
         }
        if (temp2->next == NULL)
           {
            printf("\nvalue not found");
           }
        if (temp->next->value == val)             
            {
            temp->next = temp2->next;
            free(temp2);
            }

        }

 }

void main() 
{
    node *head = NULL;
    int ch;
    int n;
    while (1) 
{
        printf("\nenter your choice\n");
        printf("1.ADD ELEMENT\n");
        printf("2.DELETE ELEMENT\n");
        printf("3.DISPLAY LIST\n");
        printf("4.EXIT\n");
        scanf("%d", &ch);
        switch (ch)
        {
            case 1:printf("\n enter data \n");
                scanf("%d", &n);
                insert(&head, n);
                display_node(&head);
                break;
            case 2:de_node(&head);
                display_node(&head);
                break;
            case 3:display_node(&head);
                break;
            case 4:exit(0);

        }
        }
        }

我的问题是在删除元素时在列表中插入任何内容之前
即当我试图在列表为空时删除一个元素
然后根据我的代码它应该打印 "list is empty....." 但它给出了分段错误。

Answer 1

问题在这里：

temp = *ptr;
temp2 = temp->next;

您已将 temp 设置为 *ptr，但您尚未检查 *ptr 是否为 NULL。因此，当您尝试使用 temp->next 取消引用它时，您会遇到段错误。

由于您稍后才使用 temp2，因此请将此行移至 while 循环之前：

temp2 = temp->next;

当我在链表中插入任何值之前选择删除选项时，出现分段错误

when i am selecting delete option before inserting any value in linked list i am getting segmentation fault error

c

linked-list

当我在链表中​​插入任何值之前选择删除选项时，出现分段错误

when i am selecting delete option before inserting any value in linked list i am getting segmentation fault error

c

linked-list

当我在链表中插入任何值之前选择删除选项时，出现分段错误