动态数组：使用realloc（）的无内存泄漏 [英] Dynamic arrays: using realloc() without memory leaks

问题描述

我用的realloc来调整分配的内存：

I use realloc to resize the memory allocated:

char **get_channel_name(void)   
{
    char **result;
    int n;

    result = (char **) 0;
    for (elem = snd_mixer_first_elem(handle), n = 0; elem; elem = snd_mixer_elem_next(elem)) {
        if (!snd_mixer_selem_is_active(elem))
            continue;
        if (snd_mixer_selem_has_playback_volume(elem) &&
            snd_mixer_selem_has_playback_switch(elem) &&
            snd_mixer_selem_has_capture_switch(elem)) {
            if (result == (char **) 0)
                result = (char **) malloc(sizeof(char *));
            else
                result = (char **) realloc(result, sizeof(char *) * (n + 1)); /* nulled but not freed upon failure */
            result[n++] = strdup(snd_mixer_selem_get_name(elem));
        }
    }

    if (result == (char **) 0)
        return NULL;

    result = (char **) realloc(result, sizeof(char *) * (n + 1)); /* nulled but not freed upon failure */
    result[n] = NULL;

    return result;
}

当我检查code。与cppcheck工具静态C / C ++ code分析，打印以下warings：

When I check code with cppcheck tool static C/C++ code analysis, printed the following warings:

Common realloc mistake: 'result' nulled but not freed upon failure

我

如何解决这两个可能的内存泄漏？

How can I fix these 2 possible memory leaks?

推荐答案

如果的realloc（）失败则返回 NULL 。

所以，如果你这样做（并假设的realloc（）将失败）

So if you do (and assuming realloc() would fail)

result = realloc(result, ...);

结果将被赋予 NULL 和它所指向的不是免费（） ED和地址为免费（） ED是丢失。

result will be assigned NULL and what it pointed to is not free()ed and the address to be free()ed is lost.

要解决这个问题吗：

void * tmp = realloc(result, ...);
if (NULL == tmp)
{
  /* Handle error case, propably freeing what result is pointing to. */
}
else
{
  result = tmp;
}

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