c中的链表，结构的结构，分段错误

Question

我试图在c中实现一个列车结构。我有一个结构称为转向架和另一个称为链接转向架。我有如何在代码中引用这些结构的所有组件的问题。我的主要问题是:

-输入转向架类型时出现segfault

-为什么转向架的尺寸是28?(char(1) +array(20) +int(4)=25)

-我想确认是否有一个结构内部的结构，我需要malloc为每一个内部结构当我做一个外部结构的实例?不管怎样，为了使它自动化。

-我是否使代码过于复杂?有没有更简洁的写法?

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct
{
    char name;
    char type[20];
    int capacity;
}BOGIE;
struct LINKED_BOGIE
{
    BOGIE* bogie_part_address;
    struct LINKED_BOGIE* link;
};
typedef struct LINKED_BOGIE LINKED_BOGIE;

void print_train(LINKED_BOGIE* engine_address);
void add_bogie(LINKED_BOGIE* engine_address);

void add_bogie(LINKED_BOGIE* engine_address)
{
    LINKED_BOGIE* traverse=engine_address;
    LINKED_BOGIE* new_bogie_address=(LINKED_BOGIE*)malloc(sizeof(LINKED_BOGIE));
    new_bogie_ad:dress->bogie_part_address=(BOGIE*) malloc(sizeof(BOGIE));
    printf("Enter bogie name,type,capacityn");
    scanf("%c%s%d",&(new_bogie_address->bogie_part_address->name),(new_bogie_address->bogie_part_address)->type,&((new_bogie_address->bogie_part_address)->capacity));

    do traverse=traverse->link;
    while(traverse->link!=NULL);
    traverse->link=new_bogie_address;
    new_bogie_address->link=NULL;
    print_train(engine_address);
}

void print_train(LINKED_BOGIE* engine_address)
{
    LINKED_BOGIE* traverse=engine_address;
    int count=0;
    printf("This is the trainn");
    printf("----------------------------------------n");

    do
    {
        printf("Bogie number:%dn",count);
        printf("Bogie name:%cn",traverse->bogie_part_address->name);
        printf("Bogie type:%sn",traverse->bogie_part_address->type);
        printf("Bogie capacity:%dn",traverse->bogie_part_address->capacity);
        printf("----------------------------------------n");
    }
    while(traverse->link!=NULL);
}
int main()
{
    printf("linked bogie size:%lun",sizeof(LINKED_BOGIE));
    printf("bogie size:%lun",sizeof(BOGIE));
    LINKED_BOGIE* engine_address=(LINKED_BOGIE*)malloc(sizeof(LINKED_BOGIE));
    engine_address->bogie_part_address=(BOGIE*)malloc(sizeof(BOGIE));
    engine_address->bogie_part_address->name='E';
    strcpy(engine_address->bogie_part_address->type,"Engine");
    engine_address->bogie_part_address->capacity=1;
    engine_address->link=NULL;
    //  print_train(engine_address);

    int choice=0;
    do
    {
        printf("Pick what you want to do:n
1)View the trainn
2)Add a bogien
3)Insert a bogien
4)Remove a bogien
5)Sort trainn
6)Swap bogiesn
7)Exitn");
        scanf("%d",&choice);
        switch (choice)
        {
            case 1:print_train(engine_address);break;
            case 2:add_bogie(engine_address);
        }
    }
    while(choice!=7);


return 0;
}

Answer 1

Mike已经解释过结构体的大小是由填充引起的。在您的系统中，int类型使用4个字节，并按4的倍数地址对齐。

你的malloc是正确的，但是在以后移除boogie时，你必须始终释放内部和外部结构体。

但是你的代码中有一些小错误:

• scanf("%c%s%d", ...)将而不是执行您期望的操作:%c可能会读取前一行的末尾，而不是第一个非空白字符。您应该使用%1s，而不要忘记空的位置:

  char name[2];
  ...
  scanf("%1s%19s%d",name,(new_bogie_address->bogie_part_address)->type,
      &((new_bogie_address->bogie_part_address)->capacity));
  new_bogie_address->bogie_part_address->name = name[0];
  

• do traverse=traverse->link; while(traverse->link!=NULL);也将不起作用:当列车只包含一个布吉时，在测试任何东西之前将导线设置为空。你应该这样做:

  while(traverse->link!=NULL) {
      traverse = traverse->link;
  }
  

• 在print_train中，您忘记移动遍历。应该是:

  while(traverse != NULL)
  {
      ....
      traverse = traverse->link;
      count += 1;
  }
  

记住:

• %c很少使用，因为它读取甚至不可打印的字符，这些字符被其他格式忽略
• do {...} while(...);如果比简单的while(...) {...}少使用，因为它至少运行一次它的主体。