C - 加载包含指向指针的指针的结构

Question

这会产生不兼容警告:

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

typedef struct
{
  int key;
  int data;
  struct htData_* next;
  struct htData_* prev;
}htData_;

typedef struct
{
  int num_entries;
  struct htData_** entries;
}ht_;

ht_* new_ht(int num_entries);
int ht_add(ht_* ht_p, int key, int data);

int main()
{
  int num_entries = 20;
  //crate a hash table and corresponding reference                                                                                                              
  ht_* ht_p = new_ht(num_entries);
  //add data to the hash table                                                                                                                                  
  int key = 1305;
  ht_add(ht_p,key%num_entries,20);

  return 0;
}

ht_* new_ht(int num_entries)
{
  ht_ *ht_p;
  ht_ ht;
  ht.num_entries = num_entries;
  ht_p = &ht;

  //create an array of htData                                                                                                                                   
  htData_ *htDataArray;
  htDataArray = (htData_*) malloc(num_entries * sizeof(htData_));
  //point to the pointer that points to the first element in the array                                                                                          
  ht.entries = &htDataArray; // WARNING HERE!!!!!!!!!!!!!!!!

  return ht_p;
}

我正在尝试将 **ptr 复制到包含 **ptr 的 struct。

更新:我的简化代码不准确，所以我发布了实际代码。

Answer 1

问题是 struct htData_和 htData_ 不是同一件事!就编译器而言，struct htData_不存在——它是一个不完整的类型。 htData_ ，另一方面，是一个 typedef对于匿名结构。有关更详细的分析，请参阅 Difference between struct and typedef struct in C++ .

因此，您收到警告是因为 ht.entries被声明为类型 struct htData_** , 但该赋值的右侧具有类型 <anonymous struct>** .要解决此问题，您需要定义 struct htData_ :

typedef struct htData_
{
    ...
} htData_;