从不兼容的指针类型(结构,链表)分配

Question

使用链接列表创建字典数据结构.

typedef struct _dictionary_entry_t
{
    const char* key;
    const char* value;
    struct dictionary_entry_t *next;
    struct dictionary_entry_t *prev;

} dictionary_entry_t;

typedef struct _dictionary_t
{   
    dictionary_entry_t *head;
    dictionary_entry_t *curr;
    int size; 

} dictionary_t;

使用函数将字典条目添加到链表.

int dictionary_add(dictionary_t *d, const char *key, const char *value)
{
    if (d->curr == NULL) //then list is empty
    {
        d->head = malloc(sizeof(dictionary_entry_t));
        d->head->key = key;  //set first dictionary entry key
        d->head->value = value; //set first dictionary entry value
        d->head->next = NULL; 
        //d->curr = d->head;
    }

    else 
    {
        d->curr = d->head;

        while (strcmp((d->curr->key), key) != 0 && d->curr != NULL) //while keys don't match and haven't reached end of list... 
        {
            d->curr = d->curr->next; 

        } 
    }


    return -1;
}

将d-> curr分配给d-> curr-> next给我警告'从不兼容的指针类型分配'.

这里我的错误是什么？curr和next都是*dictionary_entry_t类型

Answer 1

next是一个struct dictionary_entry_t *,但是d->curr一个dictionary_entry_t *又名struct _dictionary_entry_t *.注意下划线的区别.

解决此问题的一种方法是与您的下划线保持一致,声明next为:

struct _dictionary_entry_t *next;

但是,我更喜欢一种不同的方式:typedef在声明之前fing struct.然后:

typedef struct _dictionary_entry_t dictionary_entry_t;
struct _dictionary_entry_t {
    /* ... */
    dictionary_entry_t *next;
    /* ... */
};