出现内存泄漏；如何释放这个malloc？

Question

bool check(const char *word)
{
    int length = strlen(word);

    //malloc size of char times length of word plus \0
    char *lower_case = malloc(sizeof(char) * (length + 1));
    lower_case[length + 1] = '\0';

    //change characters to lowercase
    for (int i = 0; i < length; i++)
    {
        lower_case[i] = tolower(word[i]);
    }

    //generate int hash
    int index = generate_hash(lower_case);

    node_ptr trav = hashtable[index];

    while (trav != NULL)
    {
        if (strcmp(trav->word, lower_case) == 0)
        {
            return true;
        }
        trav = trav -> next;
    }
    free(lower_case);

    return false;
}

我从瓦尔格林德测试中泄漏了 27 字节的内存;如何释放它？

Answer 1

匿名用户

malloc之后立即有越界访问。

在这里，您正在越界访问:

lower_case[length + 1] = '\0';

应该是：

lower_case[length] = '\0';

检查< code>malloc是否也失败了也是一个明智的想法！

正如注释中提到的，当从循环内部返回时，也有可能发生内存泄漏。你需要解放那里:

  if (strcmp(trav->word, lower_case) == 0)
    {
        free(lower_case);
        return true;
    }

Answer 2

• lower_case[长度1]='\0'；写出界，改成[长度].
• 您缺少#include

您应该能够按照如下方式修复代码:

#include <string.h>
#include <stdlib.h>
#include <ctype.h>
#include <stdbool.h>

bool check (const char *word) 
{ 
  size_t length = strlen(word);

  char* lower_case = malloc(length + 1);
  if(lower_case == NULL)
  {
    return false;
  }

  //change characters to lowercase
  for (size_t i = 0; i < length; i++)
  {
    lower_case[i] = tolower(word[i]);
  }
  lower_case[length] = '\0'; 

  //generate int hash
  int index = generate_hash(lower_case); 
  bool result = false;
  for(const node* trav = hashtable[index]; trav!=NULL; trav=trav->next)
  {
    if (strcmp(trav->word, lower_case) == 0)
    {
        result = true;
        break;
    }
  }

  free(lower_case);
  return result;
}

需要将类型node_ptr更改为没有隐藏指针的节点。