c - 分配内存以保存 C 中的结构数组

Question

我正在尝试分配内存来保存结构数组

SERVER* topology = malloc(sizeof(struct SERVER*)* 10 );
    for (int i = 0; i < 10; ++i)
    {
        topology[i] = malloc(sizeof(struct SERVER));
    }
    PATH* paths = malloc(sizeof(struct PATH*)*10);
    for (int i = 0; i < 10; ++i)
    {
        paths[i] = malloc(sizeof(struct PATH));
    }

这些是我的结构

typedef struct{
    int id;
    char ip_addr[MAX_IP + 1];
    int port;
}SERVER;

typedef struct{
    int server1;
    int server2;
    int weight;
}PATH;

然后在我的代码中，我尝试使用

释放它

for (int i = 0; i < 10; ++i)
   {
     free(paths[i]);
   }
   free(paths);

   for (int i = 0; i < 10; ++i)
   {
     free(topology[i]);
   }
   free(topology);

我不断收到以下错误

error: invalid application of 'sizeof' to an incomplete type 'struct SERVER'
                topology[i] = malloc(sizeof(struct SERVER));
                                     ^     ~~~~~~~~~~~~~~~
:18:42: note: forward declaration of 'struct SERVER'
        SERVER* topology = malloc(sizeof(struct SERVER*)* 10 );
                                                ^
:26:21: error: invalid application of 'sizeof' to an incomplete type 'struct PATH'
                paths[i] = malloc(sizeof(struct PATH));
                                  ^     ~~~~~~~~~~~~~
:23:37: note: forward declaration of 'struct PATH'
        PATH* paths = malloc(sizeof(struct PATH*)*10);

......

c:97:11: error: passing 'PATH' to parameter of incompatible type 'void *'
         free(paths[i]);
              ^~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/stdlib.h:143:18: note: passing argument to parameter here
void     free(void *);
                    ^
:103:11: error: passing 'SERVER' to parameter of incompatible type 'void *'
         free(topology[i]);
              ^~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.11.sdk/usr/include/stdlib.h:143:18: note: passing argument to parameter here
void     free(void *);

我通常是 C 的新手。感谢任何帮助。

Answer 1

试试这个:

typedef struct SERVER {
  ....
} SERVER;

typedef struct PATH {
  ....
} PATH;

你看，你使用了 struct SERVER 和 struct PATH 但你还没有声明它们。您确实在未命名的结构上使用 typedef 声明了类型 SERVER 和类型 PATH。

或者，您可以保持结构不变，并使用 sizeof(PATH*) 和 sizeof(STRUCT*)。