Question

我有以下代码：

main()
{
    struct passenger_node {
        char *name;
        struct passenger_node *next;
    };

    struct flight {
        char airline[MAXNAME];
        int number;
        struct passenger_node *passengers;
    };

    // New passengers are added to the front of the list of passengers.
    void add_passenger(char *name, struct flight *flp) {
          struct passenger_node n;
          n.name = malloc(strlen(name)+1);
          strncpy(n.name, name, strlen(name)+1);
          n.next = flp->passengers;
    };

    void list_passengers(struct flight fl) {
        printf("%s", fl.passengers->name);
    }

    struct flight my_flight;
    strcpy(my_flight.airline, "Air");
    my_flight.number = 111;
    my_flight.passengers = NULL;
    add_passenger("MMM", &my_flight);
    list_passengers(my_flight);
}

我在函数list_passengers中的line fl.passengers-＆gt;名称出现分段错误？谁能告诉我为什么会这样？

Answer 1

您的add_passenger无法更新passengers指针：

void add_passenger(char *name, struct flight *flp) {
      struct passenger_node n;
      n.name = malloc(strlen(name)+1);
      strncpy(n.name, name, strlen(name)+1);
      n.next = flp->passengers;
      flp->passengers = ???;                 //<--- UPDATE HERE
};

您必须为此动态分配passenger_node，并且不能使用本地的。{/ p>

void add_passenger(char *name, struct flight *flp) {
      struct passenger_node *np = malloc(sizeof(struct passenger_ndoe));
      if (!np) return;

      np->name = malloc(strlen(name)+1);
      strncpy(np->name, name, strlen(name)+1);
      np->next = flp->passengers;
      flp->passengers = np;
};

您的list_passengers也不正确。它只显示第一位乘客，并且不检查空乘客名单：

void list_passengers(struct flight fl) {
    struct passenger_node *np;

    for ( np = fl.passengers; np != NULL; np = np->next )
        printf("%s\n", np->name);
}

Answer 2

如果您将list_passengers()更改为：

void list_passengers(struct flight fl) {
    assert(fl.passengers != NULL);
    printf("%s", fl.passengers->name);
}

您将看到fl.passengers == NULL，并尝试取消引用它。

Answer 3

你基本上需要这个（应该用任何C编译器编译）：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#define MAXNAME 100

struct passenger_node {
    char *name;
    struct passenger_node *next;
};

struct flight {
    char airline[MAXNAME];
    int number;
    struct passenger_node *passengers;
};


// New passengers are added to the front of the list of passengers.
void add_passenger(char *name, struct flight *flp) {
      struct passenger_node *newpassenger ;
      newpassenger = malloc(sizeof (struct passenger_node));
      newpassenger->name = malloc(strlen(name)+1);
      strncpy(newpassenger->name, name, strlen(name)+1);
      newpassenger->next = flp->passengers;
      flp->passengers = newpassenger;
};

void list_passengers(struct flight fl) {
    printf("%s", fl.passengers->name);
}

main()
{
    struct flight my_flight;
    strcpy(my_flight.airline, "Air");
    my_flight.number = 111;
    my_flight.passengers = NULL;
    add_passenger("MMM", &my_flight);
    add_passenger("XXX", &my_flight);
    list_passengers(my_flight);
}

但您仍需要使list_passengers功能正常工作。目前只打印列表中的第一位乘客。

Answer 4

C中不允许使用嵌套函数。您在main中定义了函数，这是函数 name是一个指针，你可以为它分配内存。分配menmory然后访问它并确保您不访问NULL指针。这会导致分段错误。

我的代码中的分段错误？

4 个答案: