c - 动态数组 : using realloc() without memory leaks

Question

我使用 realloc 来调整分配的内存大小:

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;
}

当我使用cppcheck工具静态C/C++代码分析检查代码时，打印了以下警告:

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

如何修复这 2 种可能的内存泄漏？

Answer 1

如果 realloc() 失败，则返回 NULL。

所以如果你这样做(假设 realloc() 会失败)

result = realloc(result, ...);

result 将被分配为 NULL 并且它指向的内容不是 free() 并且地址是 free( )ed 丢失了。

要解决此问题，请执行以下操作:

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