c - 内存泄漏检测导致错误

Question

基本上我有内存泄漏。所以我想修复它们!在一些函数中添加了free()。运行 valgrind 并收到成功消息“所有泄漏内存已修复”或类似的信息!之后我遇到了一堆错误:(我想我已经把 free() 放对了。很容易混淆，因为有节点作为指针，节点作为结构(查看 file.h)。任何帮助表示赞赏.谢谢。抱歉，如果这个问题很简单。我是初学者......

file.h 中的代码

struct node {
    int value;
    struct node * next;
};
typedef struct node List;

int is_empty(List *);
List *add_node(List *, int);
List *remove_node(List *, int);
List *create_node(int);
char *tostring(List *);

file.c 中的代码

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

#define STRSIZE 128 /*assume string representation fits*/

/* Return true if the list h is empty
 * and false otherwise.
 */
int is_empty(List *h) {
    return h == NULL;
}

/* Create a list node with value v and return a pointer to it 
 */
List *create_node(int v) {
    List *node = malloc(sizeof(List));
  free(node);
    node->value = v;
    node->next = NULL;
    return node;
}

/* Insert a new node with the value v at the 
 * front of the list. Return the new head of 
 * the list.
 */
List *add_node(List *h, int v) {
    List *node = create_node(v);
    node->next = h;
    return node;
}

/* Remove the first node in the list h that
 * has the value v.  Return the head of the
 * list.
 */
List *remove_node(List *h, int v) {
    List *curr = h;

    /* Handle the cases when list is empty or the value
     * is found at the front of the list */
    if (h == NULL) {
        return h;
    } else if (h->value == v) {
        h = h->next;
 return h;
    }

    /* Look for the value in the list (keeping the pointer to
     * the previous element so that we can remove the right 
     * element) */
    while (curr->next != NULL && curr->next->value != v) {
        curr = curr->next;
    }

    if (curr->next == NULL) { /* v is not in list so do nothing */
        return h;
    } else { /* curr->next->value == v */
        curr->next = curr->next->next;
        return h;
    }
}

/* Return a string representation of the list pointed to by h.
 */
char *tostring(List *h) {
    char *str= malloc(STRSIZE);
    char num[4]; /* assume integer has max. four digits*/
    free(str);
    str[0] = '\0';
    while (h != NULL) {
        sprintf(num, "%d", h->value);
        strncat(str, num, STRSIZE - strlen(str) - 1);
        h = h->next;
    }
    return str;
}

Answer 1

也许你想要

temp = curr->next;
curr->next = curr->next->next;
free (temp);

在代码的当前状态下，remove_node 存在泄漏(如果删除所有节点，实际上会泄漏整个列表)。

此外，为了阻止 tostring 函数中的内存泄漏，该函数的调用者有责任释放 tostring 返回的字符串。