内存泄漏双指针

Question

我无法弄清楚我在这里做错了什么。一般是 valgrind 和 C 的新手，但已经设法清理了我所有的内存泄漏，除了这个

==8749== HEAP SUMMARY:
==8749==     in use at exit: 880 bytes in 11 blocks
==8749==   total heap usage: 80 allocs, 69 frees, 5,620 bytes allocated
==8749== 
==8749== 400 bytes in 5 blocks are definitely lost in loss record 1 of 2
==8749==    at 0x4C2A2DB: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==8749==    by 0x402B1C: tokenize (tm_utility.c:78)
==8749==    by 0x402E57: load_data (tm_utility.c:188)
==8749==    by 0x400D0A: main (tm.c:57)
==8749== 
==8749== 480 bytes in 6 blocks are definitely lost in loss record 2 of 2
==8749==    at 0x4C2A2DB: malloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==8749==    by 0x402B1C: tokenize (tm_utility.c:78)
==8749==    by 0x402C97: load_data (tm_utility.c:147)
==8749==    by 0x400D0A: main (tm.c:57)
==8749== 

与此功能有关：

char** tokenize(const char* input)
{
    char* str = (char*)strdup(input);
    int count = 0;
    int capacity = 10;
    char** result = malloc(capacity*sizeof(*result)); /*LINE 78*/

    char* tok=strtok(str,",");

    while(1)
    {
        if (count >= capacity)
            result = realloc(result, (capacity*=2)*sizeof(*result));

        result[count++] = tok? strdup(tok) : tok;

        if (!tok) break;

        tok=strtok(NULL,",");
    }

    free(str);
    return result;
}

我可以看到我没有释放一些东西，但我不知道在哪里释放它（调用函数还是本地？？）以及我应该释放的究竟是什么？

帮助？

谢谢

编辑：

这是调用函数的代码。我不知道我还需要释放什么，尝试了一些不同的东西，但结果变得更糟，最后在这里发帖。

while (fgets(line, sizeof(line), coinsfile_stream) != NULL)
{

    tokens = tokenize(line);

    for(i=tokens; i && *i; ++i)
    {

        if(y==0)
        {
            tm->coins[x].denomination = atoi(*i);
            y=1;
            x++;
        }
        else
        {
            tm->coins[z].count = atoi(*i);
            y=0;
            z++;
        }
        free(*i);
    }
}

Answer 1

在load_data() 中调用tokenize() 的代码似乎负责释放。您正在将分配的空间返回给调用函数。

---

使用问题中现在显示的额外代码，您需要在处理令牌的for 循环之后添加free(tokens);。下面的代码以来自valgrind 的干净健康单运行：

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

char **tokenize(const char *input);

char **tokenize(const char *input)
{
    char *str = (char *)strdup(input);
    int count = 0;
    int capacity = 10;
    char **result = malloc(capacity*sizeof(*result)); /*LINE 78*/

    char *tok = strtok(str, ",\n");

    while (1)
    {
        printf("Found: <<%s>>\n", tok);
        if (count >= capacity)
            result = realloc(result, (capacity *= 2)*sizeof(*result));

        result[count++] = tok ? strdup(tok) : tok;

        if (!tok)
            break;

        tok = strtok(NULL, ",\n");
    }

    free(str);
    return result;
}

int main(void)
{
    char line[1024];
    int x = 0;
    int y = 0;
    int z = 0;

    struct Coin {
        int denomination;
        int count;
    };
    struct Trade {
        struct Coin coins[10];
    };
    struct Trade tm1;
    struct Trade *tm = &tm1;

    while (fgets(line, sizeof(line), stdin) != NULL)
    {
        char **tokens = tokenize(line);

        for (char **i = tokens; i && *i; ++i)
        {
            printf("Token: <<%s>>\n", *i);
            if (y == 0)
            {
                tm->coins[x].denomination = atoi(*i);
                y = 1;
                x++;
            }
            else
            {
                tm->coins[z].count = atoi(*i);
                y = 0;
                z++;
            }
            free(*i);
        }
        free(tokens);
    }
}

数据文件：

12,23
34,45
56,67

示例输出：

Found: <<12>>
Found: <<23>>
Found: <<(null)>>
Token: <<12>>
Token: <<23>>
Found: <<34>>
Found: <<45>>
Found: <<(null)>>
Token: <<34>>
Token: <<45>>
Found: <<56>>
Found: <<67>>
Found: <<(null)>>
Token: <<56>>
Token: <<67>>

注意：我的代码依赖于我正在使用的系统（Mac OS X 10.9 Mavericks；GCC 4.8.2 — 但 valgrind 在同一平台上托管的古老 Linux VM 中运行）在被要求打印时不会崩溃空指针指向的字符串。您需要查看while (1) 循环；您可能应该将其更改为 while (tok != 0) 或等效项。完成此操作后，您也可以简化循环体；现在有两个多余的空值测试。