c - char* 数组中的元素在复制到新数组时损坏

Question

我以前遇到过这个问题，答案是要么以 null 终止字符串，要么确保为字符串分配足够的内存。这是相关的代码片段:

for (z; z<mountable_volumes; z++)
{
main_items[z] = malloc(strlen(volumes[z])+2);
main_items[z] = volumes[z];
printf("main_items[%i]: %s\n", z, volumes[z]);
}
main_items[z] = NULL;
return main_items;

Volumes[] 是正确的，但是当它的内容被创建到 main_items[] 中时，它就变坏了。我试过玩 malloc，甚至直接分配比必要更多的内存。我还尝试在每个 main_items[] 元素的末尾添加一个 '\0'。我尝试使用 strcpy、strncpy、sprintf 得到相同的结果。

这是我程序的日志:

volumes[0]: Unmount /sdcard
volumes[1]: Mount /system
volumes[2]: Unmount /cache
volumes[3]: Mount /data
volumes[0]: Unmount /sdc)☻
main_items[1]: Mount /syste)☻
main_items[2]: Unmount /cac‼
main_items[3]: Mount /data

我错过了什么？谢谢!如果需要，我可以粘贴更多功能。

编辑:

这是整个函数:(我已经应用了 strndup() 和 free() 技巧)

char** get_mount_menu_options()
{
  Volume * device_volumes = get_device_volumes();
  num_volumes = get_num_volumes();

  char** volumes = malloc (num_volumes * sizeof (char *));

  int mountable_volumes = 0;
  int usb_storage_enabled = is_usb_storage_enabled();

  int i;
  for (i=0; i<num_volumes; i++)
  {
    volumes[i] = "";
    Volume *v = &device_volumes[i];
    char* operation;
if (is_path_mountable(v->mount_point) != -1)
      {   
    if (is_path_mounted(v->mount_point)) operation = "Unmount";
    else operation = "Mount";
    volumes[mountable_volumes] = malloc(sizeof(char*));
    printf("volumes[%i]: %s %s\n", mountable_volumes, operation, v->mount_point);
    sprintf(volumes[mountable_volumes], "%s %s", operation, v->mount_point);
    mountable_volumes++;
  }
}

char **main_items = malloc (num_volumes * sizeof (char *));

int z;
for (z=0; z<mountable_volumes; z++)
{     
main_items[z] = strndup(volumes[z], strlen(volumes[z]));
free(volumes[z]);
printf("main_items[%i]: %s\n", z, volumes[z]);
}
main_items[z] = NULL;
return main_items;
}

当前日志:

volumes[0]: Unmount /sdcard
volumes[1]: Mount /system
volumes[2]: Unmount /cache
volumes[3]: Mount /data
main_items[0]: Unmount /sdc)☻
main_items[1]: Mount /syste)☻
main_items[2]: Unmount ¿♠
main_items[3]:

谢谢大家!

Answer 1

要复制字符串，您需要使用strcpy()。分配不起作用!

strcpy(main_items[z], volumes[z]);

此外，

main_items[z] = malloc(strlen(volumes[z])+2);

应该是

main_items[z] = (char *) malloc(strlen(volumes[z]) + 1);

我假设 main_items[z] 和 volumes[z] 是一个 char *