C結構體的不完整類型

Question

我試圖採用RRhead，在RRhead上有一個新的RCB點，因爲它是下一個，並且在新的RCB處有RRhead點，因爲它是先前的點。

typedef struct{ 
    int sequence_number; 
    int file_descriptor; 
    FILE *requested_file; 
    int bytes_remaining; 
    int quantum; 
    struct RCB *next; 
    struct RCB *prior; 
} RCB; 

typedef struct RCB RCB; 


RCB *RRhead = NULL; 


static void admit_to_scheduler_RR(int fd, FILE *fin){ 
int sequence_counter, new_bytes_remaining, new_quantum = 0; 
    RCB new_rcb = {sequence_counter, fd, fin, new_bytes_remaining, new_quantum, RRhead, NULL}; 
    RRhead->prior = &new_rcb; 
    RRhead = &new_rcb; 
    sequence_counter++; 
} 

產生以下錯誤：

sws.c: In function ‘admit_to_scheduler_RR’: 
sws.c:318:10: error: variable ‘new_rcb’ has initializer but incomplete type 
    struct RCB new_rcb = {sequence_counter, fd, fin, new_bytes_remaining, new_quantum, RRhead, NULL}; 
     ^
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:10: warning: excess elements in struct initializer [enabled by default] 
sws.c:318:10: warning: (near initialization for ‘new_rcb’) [enabled by default] 
sws.c:318:14: error: storage size of ‘new_rcb’ isn’t known 
    struct RCB new_rcb = {sequence_counter, fd, fin, new_bytes_remaining, new_quantum, RRhead, NULL}; 
      ^
sws.c:319:9: error: dereferencing pointer to incomplete type 
    RRhead->prior = &new_rcb; 
     ^

我不知道爲什麼我收到了多餘的元素警告線索。我沒有正確初始化new_rcb嗎？我是否需要創建它，然後將所有字段設置爲我想要的？

我相信這一切都與new_rcb有一個「不完整的類型」有關。大多數使用Google表示這是因爲編譯器不知道RCB的大小應該是多少。它似乎表明我需要將此結構定義放入一個標題中。這是絕對必要的嗎？

Answer 1

在第一個聲明中，您聲明RCB是struct使用typedef。直接後來，你說，'順便說一句，RCB意味着struct RCB'，這是沒有定義在這一點！ （對於存在的，你不得不說struct RCB { ... };代替。）

---

基本上，刪除typedef struct RCB RCB;這將擺脫對相關錯誤的，但新會彈出。

Answer 2

嘗試你的結構更改爲以下（即刪除typedef關鍵字）：

struct RCB { 
    int sequence_number; 
    int file_descriptor; 
    FILE *requested_file; 
    int bytes_remaining; 
    int quantum; 
    struct RCB *next; 
    struct RCB *prior; 
}; 

的更多信息可以在這個答案讀給Difference between 'struct' and 'typedef struct' in C++?。

Answer 3

嘗試這樣：

typedef struct RCB RCB; 
strutc RCB { 
.... 

「標籤」命名空間中的C（與struct和union推出）是從標識符名字空間不同。使用typedef，您還可以將標識符RCB與類型struct RCB關聯。

Answer 4

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

typedef struct RCB RCB; 

typedef struct RCB { 
    int sequence_number; 
    int file_descriptor; 
    FILE *requested_file; 
    int bytes_remaining; 
    int quantum; 
    RCB *next; 
    RCB *prior; 
} RCB; 

RCB new_rcb = {11, 21, NULL, 31, 41, NULL, NULL};; 

static void admit_to_scheduler_RR(int fd, FILE *fin) { 

    int sequence_counter = 0; 
    int new_bytes_remaining, new_quantum = 0; 
    RCB *RRhead = &new_rcb; 
    RRhead->prior = &new_rcb; 
    sequence_counter++; 
} 

int main(int argc, char *argv[]) { 

    admit_to_scheduler_RR(1, NULL); 
    return 0; 
} 

要修復你的錯誤，你需要更改您的代碼類似於上面的東西，它使用你的數據結構和編譯。