编译错误：没有东西结构或联合申请为会员 [英] compilation error: request for member in something not a structure or union

问题描述

编辑： 的code以下已被修改，这个问题已经得到解决工作的

的具体来说，（* hardwareList.next_item） - ＆gt;接下来最初编写不带括号（例如，作为 * hardwareList.next_item- ＆gt;接着）和编译器不明白的

我想锻炼为什么编译器是越来越有我的C code混淆。我试图创建一个存储的所有项目，也是一个指针地址的最后下一个变量，简单的追加一个链表。

  typedef结构{
  INT recordNum;
  字符工具名[25];
  INT数量;
  浮动费用;
} HardwareData;typedef结构_HardwareListItem {
  HardwareData数据;
  结构_HardwareListItem *接下来的;
} HardwareListItem;typedef结构_HardwareList {
  HardwareListItem *物品;
  HardwareListItem ** NEXT_ITEM;
} HardwareList;HardwareList readFromFile（FILE * FP）
{
  焦炭STO preading = 0;
  HardwareList hardwareList = {0};
  hardwareList.next_item =安培; hardwareList.items;
  做{
    * hardwareList.next_item =（HardwareListItem *）释放calloc（1，sizeof的（HardwareData））;
    如果（* hardwareList.next_item == NULL）
    {
      fprintf中（标准错误，OOM阅读文件\\ n）;
      fflush（标准错误）;
      出口（EXIT_FAILURE）;
    }
    如果（的fread（及（（* hardwareList.next_item） - ＆GT;！数据），的sizeof（HardwareData），1，FP）= 1）{
      免费（* hardwareList.next_item）;
      * hardwareList.next_item = NULL;
      STO preading = 1;
    }其他{
      hardwareList.next_item =及（（* hardwareList.next_item） - ＆gt;接着）;
    }
  }而（STO preading！）;  返回hardwareList;
}
 

编译器说：

 第31行：错误：请求的东西不是一个结构或联合成员数据
第36行：错误：没有东西结构或联合要求会员'下一个'
 

解决方案

我的猜测，问题是这片code的： *（hardwareList.next_item） - GT;数据

NEXT_ITEM 是一个指针的指针，所以我的猜测是，编译器读取此为 *（（hardwareList.next_item） - GT;数据）这当然行不通 - 指针没有任何成员用C

尝试（（*（hardwareList.next_item）） - GT;数据）。来得到正确的解引用顺序

Edit: The code below has been modified to work as the problem has been solved.

Specifically, (*hardwareList.next_item)->next was originally written without brackets (e.g. as *hardwareList.next_item->next) and the compiler didn't understand it.

I'm trying to workout why the compiler is getting confused with my C code. I'm trying to create a linked list that stores all the items and also a pointer to the address-of the last "next" variable, for easy appending.

typedef struct {
  int recordNum;
  char toolName[25];
  int quantity;
  float cost;
} HardwareData;

typedef struct _HardwareListItem{
  HardwareData data;
  struct _HardwareListItem* next;
} HardwareListItem;

typedef struct _HardwareList {
  HardwareListItem* items;
  HardwareListItem** next_item;
} HardwareList;

HardwareList readFromFile(FILE* fp)
{
  char stopReading = 0;
  HardwareList hardwareList = {0};
  hardwareList.next_item = &hardwareList.items;
  do {
    *hardwareList.next_item = (HardwareListItem*)calloc(1, sizeof(HardwareData));
    if (*hardwareList.next_item == NULL)
    {
      fprintf(stderr, "OOM Reading File\n");
      fflush(stderr);
      exit(EXIT_FAILURE);
    }
    if (fread(&((*hardwareList.next_item)->data), sizeof(HardwareData), 1, fp) != 1) {
      free(*hardwareList.next_item);
      *hardwareList.next_item = NULL;
      stopReading = 1;
    } else {
      hardwareList.next_item = &((*hardwareList.next_item)->next);
    }
  } while(!stopReading);

  return hardwareList;
}

Compiler says:

line 31: error: request for member 'data' in something not a structure or union
line 36: error: request for member 'next' in something not a structure or union

解决方案

My guess the problem is this piece of code: *(hardwareList.next_item)->data

next_item is a pointer to a pointer, so my guess is that the compiler reads this as *((hardwareList.next_item)->data) which of course doesn't work - pointers don't have any members in C.

Try ((*(hardwareList.next_item))->data) to get the correct dereference order.

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