試圖免費結構元素

Question

我有釋放被定義爲一個結構的一個實例的元素相關聯的內存問題

當指針錯誤如下：

typedef struct WebPage { 
    char *url;        // url of the page 
    char *html;        // html code of the page 
    size_t html_len;       // length of html code 
    int depth;        // depth of crawl 
} WebPage; 

我嘗試釋放它使用：

static void setDestroy(set_t *set){ 

    pair_t *temp2; 

    if(set!=NULL&&set->head!=NULL){ 
    //store the head in a temporary pair 
    pair_t *temp = set->head; 
    //cycle through LL items, freeing contents and then structure instances 
    while(temp!=NULL){ 
     temp2 = temp->next; 
     free(temp->data->url); 
     free(temp->data->html); 
     free(temp->data); 
     free(temp->key); 
     free(temp); 
     temp = temp2; 
    } 
    set->head = NULL; 
    } 

    free(set); 
    return; 

} 

但是我得到這個錯誤：

gcc -Wall -pedantic -std=c11 -ggdb -c -o crawler.o crawler.c 
crawler.c: In function ‘setDestroy’: 
crawler.c:428:22: warning: dereferencing ‘void *’ pointer 
     free(temp->data->url); 
        ^
crawler.c:428:22: error: request for member ‘url’ in something not a structure or union 
crawler.c:429:22: warning: dereferencing ‘void *’ pointer 
     free(temp->data->html); 
        ^
crawler.c:429:22: error: request for member ‘html’ in something not a structure or union 
<builtin>: recipe for target 'crawler.o' failed 

什麼我可能會被錯誤地做任何想法？我試圖將temp-> data-> url作爲一個字符串無效。

謝謝！

Answer 1

由於錯誤消息說，temp->data是void*，因此您不能使用temp->data->html和temp->data->url。您需要將其轉換爲WebPage*以訪問這些成員。

free(((WebPage*)temp->data)->html); 
free(((WebPage*)temp->data)->url);