C错误：请求成员___不是结构或联合

Question

So the code is saying that List and size is not a structure?

typedef struct HashTable{
    int size;
    ListRef **List; 
} hash;

typedef struct hash *hash_ref;

hash_ref *newHash(int size){
    hash_ref *hashed= NULL;
    if(size<1){
        return NULL;
    }
    if( (hashed=malloc(sizeof(hash))) ==NULL){
        return NULL;
    }
    if( (hashed->List=malloc(sizeof(ListRef*)*size)) ==NULL){
        return NULL;
    }
    for(int i=0; i<size; i++){
        hashed->List[i]=NULL;
    }
    hashed->size=size;

    return hashed;
}

Here is my List function

typedef struct Node{
    long key;/*book id*/
    ListRef data;
    struct Node* next;
    struct Node* prev;
}NodeType;

typedef NodeType* NodeRef;

typedef struct ListHdr{
    NodeRef first;
    NodeRef last;
    NodeRef current;
    long length;
}ListHdr;

I was wondering whats up with this error? I forgot to add that ListHdr is changed to ListRef in my List header file.. Which is included in my hashtable module.

I'm currently trying to create 2 hash tables. One has table stores 2 long integers. The other hashtable takes 1 long integer and a linked list(which has 2 long integers).

Answer 1

hash_ref is typedefed to a pointer to hash , so you must declare hashed as hash_ref hashed , not hash_ref *hashed . (The latter would effectively create a pointer to pointer to hash .)

In addition to this, you should omit struct from the typedef that declares hash_ref . Currently hash_ref isn't declared to point hash , but to an as-yet-undeclared struct hash . That compiles only because the compiler interprets it as a forward declaration of a struct hash . This interpretation will cause any code that tries to dereference hash_ref to fail with errors such as "storage size of struct hash unknown".

Answer 2

It means you're either calling . on something that isn't a struct or union OR -> on a pointer that isn't a pointer directly to a struct or union.

hash_ref * hashed is a DOUBLE pointer to HashTable. A single dereference still gives you a HashTable pointer, which isn't a union or struct.