c - 双向链表插入段错误 - C

Question

我有一个作业是写先到先得和循环法模拟并比较它们。我开始创建用于制作事件列表的链表。我制作了 insert 和 print_list 函数，但无法正常工作。我的 friend 告诉我使用双向链表，所以我重新创建了链表并试图使插入函数起作用。我解决了大部分问题，但我现在找不到我的插入函数有什么问题。当我比较是否插入指针数据和当前指针数据时，我的 While 循环语句出现段错误。我查看了我的 C 书，它与我有相似的代码，也通过这里的双向链表段错误 -C 问题，但仍然无法得到我的错误。

这是我的输出

-bash-3.2$ ./main 3 100
please enter the process-id, arrival-time and cpu-time.
1 2 3 4
something
something
DONE1
DONE2
DONE3
DONE4
Segmentation fault

由于打印了test4(DONE4)而下一个测试没有，这意味着我在这部分有错误

while((currentptr->arrivaltime < newpointer->arrivaltime) && currentptr != NULL)

你能帮帮我吗？我的代码有什么问题？

struct event {
   struct event *next;
   int processid;
   int arrivaltime;
   int cputime;
};
typedef struct event Event;
typedef Event *eventPtr;

Event create_node(int processid, int arrivaltime, int cputime);
void add_event(Event *newpointer, eventPtr *eventlist);
void print_node(Event node);
void print_eventlist(Event *eventlist);
Event get_nextevent(Event *eventlist);

int main(int argc, char* argv[])
{
int sourcenum,a,b,c,i;
Event tempevent;
eventPtr eventlist = NULL;
print_eventlist(&(*eventlist));
char* sources,timeSlice;
if(argc != 3)
printf("Proper usage is: main.c sources time-slice\n");
else
{
    sourcenum = atoi(argv[1]);
    timeSlice = atoi(argv[2]);
    for(i = 0; i < sourcenum ; i++)
    {
          //print_eventlist(&(*eventlist));
          printf("please enter the process-id, arrival-time and cpu-time.\n");
          scanf("%d %d %d",&a, &b, &c);
          printf("something\n");
          tempevent = create_node(a,b,c);
          print
          printf("something\n");
          add_event(&tempevent, &eventlist);
    }

}
return 0;
}


void add_event(Event *newpointer, eventPtr *eventlist)     //insert
{
 printf("DONE1\n");
 eventPtr currentptr, prevptr;
 printf("DONE2\n");
 prevptr = NULL;
 printf("DONE3\n");
 currentptr = *eventlist;
 printf("DONE4\n");
 while((currentptr->arrivaltime < newpointer->arrivaltime) && currentptr != NULL)                  /*on every loop previous and current pointer gets upgraded*/
 {
         printf("DONEW\n");
         prevptr = currentptr;
         currentptr = currentptr->next;   
 }
 printf("DONEW\n");
 if(prevptr != NULL)
 {
     printf("DONEW\n");
     prevptr->next = newpointer;
     newpointer->next = currentptr;
 }
 else
 {
     printf("DONEW\n");
     newpointer->next = *eventlist;                      //?????
     *eventlist = newpointer;
 }
 printf("DONE\n");
}

Answer 1

您声明问题最有可能出现在

while((currentptr->arrivaltime < newpointer->arrivaltime) && currentptr != NULL)

您要测试 currentptr!=NULL 的事实意味着它可能为 NULL。但如果它是那么你的条件的早期部分将失败。首先测试 NULL，然后进行比较的后半部分...:

while(currentptr != NULL && (currentptr->arrivaltime < newpointer->arrivaltime))