[英]When freeing a pointer for a nested struct getting Segmentation fault
這是我的代碼:
#include <stdio.h>
#include <ctype.h>
#include <string.h>
#include <stdlib.h>
#define NAMESIZE 20
#define LINESIZE 1024
typedef struct name name;
struct name
{
char last[NAMESIZE]; /* last name */
char first[NAMESIZE]; /* first name*/
};
typedef struct record record;
struct record
{
name name;
int score;
};
typedef struct record_list record_list;
struct record_list
{
record *data; /* the dynamic array of records */
size_t nalloc; /* number of records allocated */
size_t nused; /* number of records in use */
};
void list_init(record_list *list)
{
list -> data = 0;
list -> nalloc = 0;
list -> nused = 0;
}
int list_insert(record_list *list, const record *rec)
{
size_t newSize;
record *tmp;
if(list -> nalloc == list -> nused)
{
if(list -> nalloc == 0)
{
newSize = 1;
}
else
{
newSize = 2 * list -> nalloc;
}
tmp = realloc(list -> data, newSize * sizeof(record));
if(tmp == 0)
{
return 0;
}
list -> data = tmp;
list -> nalloc = newSize;
}
list -> data[list -> nused++] = *rec;
return 1;
}
void list_destroy(record_list *list)
{
printf("Attempting Deletion");
free(list->data);
free(list->nalloc);
free(list->nused);
list -> data = 0;
list -> nalloc = 0;
list -> nused = 0;
}
int main(void){
record_list list;
record *r;
name n;
int score;
char input[NAMESIZE];
char name[NAMESIZE];
char lname[NAMESIZE];
list_init(&list);
while(input != NULL) {
printf("Please enter a value for Name: ");
scanf("%s", input);
strcpy(input, name);
printf("Enter last name: ");
scanf("%s", input);
strcpy(input, lname);
printf("Enter score: ");
scanf("%d", &score);
r=(record*)malloc(sizeof(record));
if(r == NULL){
printf("There isn't enough memory.\n");
}
strcpy(n.first, name);
strcpy(n.last, lname);
r -> name = n;
list_insert(&list, r);
printf("\n");
printf("Choose next action:\n");
printf("\tTo add more type \"add\";\n");
printf("\tTo delete all records type \"del\";\n");
scanf("%s", input);
if(strcmp(input, "del") == 0){
list_destroy(&list);
printf("Deleted");
break;
}
}
return 1;
}
我正在做一個小型實驗室練習,在該練習中,我們制作了一個結構,填充並在用戶需要時清除它。 昨天一切正常,但今天我似乎沒有保存它或破壞了某些東西,因為我遇到了很多錯誤。 這是我收到的錯誤的示例:
本質上,當我調用一個方法時
void list_destroy(record_list *list);
它在到達第一個打印語句之前崩潰,這意味着我在方法調用中做錯了什么。
總結的問題:可能導致分段錯誤的原因(我在哪里訪問不正確的內存),或者在不使用free的情況下如何清除結構內存?
非常感謝你。
這應該說明您的問題是:
code.c: In function 'list_destroy':
code.c:74: warning: passing argument 1 of 'free' makes pointer from integer without a cast
code.c:75: warning: passing argument 1 of 'free' makes pointer from integer without a cast
您正在嘗試釋放int字段。 您不能釋放它們,因為它們不是指向內存塊的指針。
因此,刪除以下代碼行:
free(list->nalloc);
free(list->nused);
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