在c中創建多文件程序時出錯

Question

我正在嘗試用 C 語言創建一個大型的多文件程序，但出現錯誤。

該程序實際上是一個智能電話簿，可以執行多項任務，例如列出、添加、搜索和刪除姓名。

對於這些任務中的每一個，我都創建了一個文件，其中包含執行任務所需的函數和變量。

這是我完成編碼的文件：

(1) us-names.txt （存儲名稱的數據庫）：

Mohammed
Ali
Harry
Peter
Hussain
Mark
John
Yu
Mohammed
Christina
Mohammed
Fatima

（2） Request.c文件（接收用戶的請求並執行需要的任務）：

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <stdint.h>
#include <string.h>

//node declaration:
typedef struct node
{
    char name[20];
    struct node* link;
}
node;

void import_names(void) ;
void add_name(string name) ;
void search_for(string name) ;
void delete_name(string name) ;


int main(int argc , string argv[])
{
    //create the hashtable and import the names:
    import_names() ;
    //check if there is any mistake in the command:
    if(argc != 3 || argc != 4)
    {
        printf("Could not recognize the command, please enter one of the three commands: \n ./phone add name \n ./phone search-for name \n ./phone delete name \n") ;
        return 1 ;
    }

    //otherwise, preform the command:
    if(strcmp(argv[1] , "add") == 0)
    {
        add_name(argv[2]) ;
        return 0 ;
    }

    if(strcmp(argv[1] , "search-for") == 0)
    {
        search_for(argv[2]) ;
        return 0 ;
    }

    if(strcmp(argv[1] , "delete") == 0)
    {
        delete_name(argv[2]) ;
        return 0 ;
    }

    else
    {
        printf("Could not recognize the command, please enter one of the three commands: \n ./phone add name \n ./phone search-for name \n ./phone delete name \n") ;
        return 1 ;
    }
}

3- Import.c 文件（從文本文件中導入名稱並將它們散列並將它們存儲在散列表中）：

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <stdint.h>
#include <string.h>

//node declaration:
typedef struct node
{
    char name[20];
    struct node* link;
}
node;

unsigned int hash(char* buffer , unsigned int CAPACITY) ;

void import_names(void)
{
    //declarations:
    FILE* fp = fopen("us-names.txt" , "a+") ;
    if(fp == NULL)
    {
        printf("CANNOT OPEN THE FILE !\n") ;
        fclose(fp) ;
        exit ;
    }

    char buffer[20] ;
    unsigned int key = 0;
    unsigned int CAPACITY = 100 ;
    struct node* temp = NULL ;
    struct node* hashtable[CAPACITY] ;
    for(int i = 0 ; i < CAPACITY ;i++)
    {
        hashtable[i] = NULL ;
    }
    struct node* curr = NULL ;
    int num_of_names = 0;

    //use a loop to iterate over the FILE:
    for(int i = 0 ; !feof(fp) ; i++)
    {
        //Import name from the FILE & store into buffer:
        fgets(buffer , 20 , fp) ;
        //pass the name into the hash_function and get the key:
        key = hash(buffer , CAPACITY) ;

        //put the name in a node then in it's right place in the hashtable using the key:
        temp = malloc(sizeof(struct node)) ;
        sprintf(temp->name , "%s" , buffer) ;
        temp->link = NULL ;

        //if the key place of the hashtable is already populated, preform the collision protocol!:
        if(hashtable[key] != NULL)
        {
            for(curr = hashtable[key] ; curr->link != NULL ; curr = curr->link)
            {

            }
            curr->link = temp ;
        }
        //else if it's unpopulated, just store the name in this place:
        else
        {
            hashtable[key] = temp ;
        }
        num_of_names++ ;
    }

    //close the FILE :
    fclose(fp) ;
}

4- Hash.c 文件（一個包含散列函數的小文件）：

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <stdint.h>
#include <string.h>

unsigned int hash(char* buffer , unsigned int CAPACITY)
{
    unsigned int sum = 0 ;
    for(int i = 0; buffer[i] != '\0' ;i++)
    {
        sum += buffer[i] ;
    }
    return sum % CAPACITY ;
}

5- Search.c 文件（包含一種用於搜索任何名稱的二進制搜索功能）：

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <stdint.h>
#include <string.h>
#include "phonehead.h"
//node declaration:
typedef struct node
{
    char name[20];
    struct node* link;
}
node;

unsigned int CAPACITY = 100 ;
struct node* hashtable[CAPACITY] ;

unsigned int hash(char* buffer , unsigned int CAPACITY) ;

void search_for(string name)
{
    //hash the name to get the place in which the wanted name is stored in the hash function:
    unsigned int place = hash(name,CAPACITY);

    //go to the location in the hashtable in which the name is stored, and check if the name is in the first node of the chain.
    if(strcmp(hashtable[place]->name , name) == 0)
    {
        printf("FOUND\n") ;
    }
    //else, go to the node pointed by the current node and check if it contain the wanted name, and repeat this step until reaching null.
    else if(strcmp(hashtable[place]->name , name) != 0)
    {
       struct node* curr = NULL ;
       for(curr = hashtable[place]->link ; curr != NULL ; curr = curr->link)
       {
           if(strcmp(curr->name , name) == 0)
           {
               printf("FOUND\n");
               exit ;
           }
       }
       printf("NOT FOUND!\n") ;
    }

}

除了頭文件：

#include <stdio.h>
#include <stdlib.h>
#include <cs50.h>
#include <stdint.h>
#include <string.h>

typedef struct node
{
    char name[20];
    struct node* link;
}
node;
unsigned int hash(char* buffer , unsigned int CAPACITY) ;
unsigned int CAPACITY = 100 ;
struct node* hashtable[CAPACITY] ;
void import_names(void) ;
void add_name(string name) ;
void search_for(string name) ;
void delete_name(string name) ;

但是當嘗試使用命令鏈接/編譯文件時

gcc phonehead.h requist.c Import.c Hash.c Search.c -o phone

我收到這些錯誤：

phonehead.h:15:14: error: variably modified ‘hashtable’ at file scope
   15 | struct node* hashtable[CAPACITY] ;
      |              ^~~~~~~~~
In file included from Search.c:6:
phonehead.h:15:14: error: variably modified ‘hashtable’ at file scope
   15 | struct node* hashtable[CAPACITY] ;
      |              ^~~~~~~~~
Search.c:8:16: error: redefinition of ‘struct node’
    8 | typedef struct node
      |                ^~~

Answer 1

本聲明

struct node* hashtable[CAPACITY] ;

在文件范圍內聲明一個可變長度數組。 您不能在文件范圍內聲明可變長度數組。 在文件作用域中聲明的對象具有靜態存儲持續時間，但可變長度數組可能只有自動存儲持續時間，即它們被允許在塊作用域中定義。

而不是聲明用作數組大小的變量CAPACITY導致聲明可變長度數組

unsigned int CAPACITY = 100 ;
struct node* hashtable[CAPACITY] ;

你可以使用像這樣的定義指令

#define CAPACITY 100
struct node* hashtable[CAPACITY] ;

或像這樣的數字常數

enum { CAPACITY = 100 };
struct node* hashtable[CAPACITY] ;

此外，您在文件范圍內兩次聲明了這樣的數組：在頭文件phonehead.h和包含頭文件的文件Search.c中。 兩次聲明數組是沒有意義的。 你應該只聲明一次。 由於文件范圍內的數組未顯式初始化，因此此類聲明引入了暫定定義。

你兩次定義了結構節點

typedef struct node
{
    char name[20];
    struct node* link;
}
node;

在標題phonehead.h和包含標題的模塊中