c - 无法将数据添加到双向链表的 C 实现中 : Segmentation Fault

Question

我有以下程序，我试图创建一个双向链表来存储有关 MP3 文件的数据。但是，当我编译并运行该程序时，我收到“段错误”。不确定该怎么办!有人可以帮忙吗？这是我的代码:

/*
 * C Program to Implement a Doubly Linked List & provide Insertion, Deletion & Display Operations
 */
#include <stdio.h>
#include <stdlib.h>

struct MP3
{
    struct MP3 *prev;
    char *artist;
    char *album;
    char *song_title;
    char *release_date;
    int runtime;
    struct MP3 *next;
}*h,*temp,*temp1,*temp2,*temp3;

void insert1();
void insert2();
void traversebeg();
void traverseend();
void delete();

int count = 0;

void main()
{
    int ch;

    h = NULL;
    temp = temp1 = NULL;

    printf("\n 1 - Insert at beginning");
    printf("\n 2 - Insert at end");
    printf("\n 3 - Delete ");
    printf("\n 4 - Display from beginning");
    printf("\n 5 - Display from end");
    printf("\n 6 - Exit");

    while (1)
    {
        printf("\n Enter choice : ");
        scanf("%d", &ch);
        switch (ch)
        {
        case 1:
            insert1();
            break;
        case 2:
            insert2();
            break;
        case 3:
            delete();
            break;
        case 4:
            traversebeg();
            break;
        case 5:
            temp2 = h;
            if (temp2 == NULL)
                printf("\n Error : List empty to display ");
            else
            {
                printf("\n Reverse order of linked list is : ");
                traverseend();
            }
            break;
        case 6:
            exit(0);
        default:
            printf("\n Wrong choice menu");
        }
    }
}

/* TO create an empty node */
void create()
{
    int data;

    temp =(struct MP3 *)malloc(1*sizeof(struct MP3));
    temp->prev = NULL;
    temp->next = NULL;
    printf("\n Enter Artist Name to database : ");
    scanf("%s", temp->artist);
    printf("\n Enter Album Name to database : ");
    scanf("%s", temp->album);
    printf("\n Enter Song Name to database : ");
    scanf("%s", temp->song_title);
    printf("\n Enter Release Date to database : ");
    scanf("%s", temp->release_date);
    printf("\n Enter runtime to database : ");
    scanf("%d", temp->runtime);
    count++;
}

/*  TO insert at beginning */
void insert1()
{
    if (h == NULL)
    {
        create();
        h = temp;
        temp3 = h;
    }
    else
    {
        create();
        temp->next = h;
        h->prev = temp;
        h = temp;
    }
}

/* To insert at end */
void insert2()
{
    if (h == NULL)
    {
        create();
        h = temp;
        temp1 = h;
    }
    else
    {
        create();
        temp1->next = temp;
        temp->prev = temp1;
        temp1 = temp;
    }
}


/* To delete an element */
void delete()
{
    int i = 1, pos;

    traversebeg();
    printf("\n Enter position to be deleted : ");
    scanf("%d", &pos);
    temp2 = h;

    if ((pos < 1) || (pos >= count + 1))
    {
        printf("\n Error : Position out of range to delete");
        return;
    }
    if (h == NULL)
    {
        printf("\n Error : Empty list no elements to delete");
        return;
    }
    else
    {
        while (i < pos)
        {
            temp2 = temp2->next;
            i++;
        }
        if (i == 1)
        {
            if (temp2->next == NULL)
            {
                printf("Node deleted from list");
                free(temp2);
                temp2 = h = NULL;
                return;
            }
        }
        if (temp2->next == NULL)
        {
            temp2->prev->next = NULL;
            free(temp2);
            printf("Node deleted from list");
            return;
        }
        temp2->next->prev = temp2->prev;
        if (i != 1)
            temp2->prev->next = temp2->next;    /* Might not need this statement if i == 1 check */
        if (i == 1)
            h = temp2->next;
        printf("\n Node deleted");
        free(temp2);
    }
    count--;
}

/* Traverse from beginning */
void traversebeg()
{
    temp2 = h;

    if (temp2 == NULL)
    {
        printf("List empty to display \n");
        return;
    }
    printf("\n Linked list elements from begining : ");

    while (temp2->next != NULL)
    {
        printf(" %s \n", temp2->artist);
        printf(" %s \n", temp2->album);
        printf(" %s \n", temp2->song_title);
        printf(" %s \n", temp2->release_date);
        printf(" %d \n", temp2->runtime);
        temp2 = temp2->next;
    }
    printf("\n %d Entries in the Database ", count);
}

/* To traverse from end */
void traverseend()
{
    temp2 = h;
    while (temp2 != temp3)
    {
        printf(" %s \n", temp2->artist);
        printf(" %s \n", temp2->album);
        printf(" %s \n", temp2->song_title);
        printf(" %s \n", temp2->release_date);
        printf(" %d \n", temp2->runtime);
        temp2 = temp2->prev;
    }
}

Answer 1

您还必须分配:

char *artist;
char *album;
char *song_title;
char *release_date;

当您分配 struct MP3 时，它不会同时分配内部参数。您可以像这样修改 create() 函数:

temp =(struct MP3 *)malloc(1*sizeof(struct MP3));
#define MAX_LEN 100
temp->artist =(char *)malloc(MAX_LEN*sizeof(char));
temp->album =(char *)malloc(MAX_LEN*sizeof(char));
temp->song_title =(char *)malloc(MAX_LEN*sizeof(char));
temp->release_date =(char *)malloc(MAX_LEN*sizeof(char));

其中 MAX_LEN 是所有这些字符串的最大长度。

scanf 中还缺少 &:temp->runtime 是一个整数，因此必须在前面加上 & 才能读取它。

scanf("%d", &(temp->runtime));