fwrite()参数问题求助
本帖最后由 nain001 于 2013-05-22 22:14:47 编辑

typedef struct student{
    char number[11];
    char name[11];
    char sex;      
    int age;
}Item;

typedef struct node{
    Item item;
    struct node * next;   
}Node;

typedef  Node * List;

/*  将List写入文件  */
void WriteToFile(const List * plist,char * filename){
    Node * pnode = *plist; 
    FILE * fp;
    int count=0;
    if((fp = fopen(filename,"w+b"))==NULL){
        fprintf(stderr,"%s 无法打开！,写入文件失败.\n",filename);
        exit(1);       
    }   
    while(pnode!=NULL){
        fwrite(pnode->item,sizeof(Item),1,fp);//这行报错，参数不对，要怎么改呢？第一个参数不可以这样吗？
        pnode = pnode -> next; 
        count++;                  
    }
    fclose(fp);
    printf("有%d条记录被写入文件\"%s\"中.\n",count,filename);
} 

[解决办法]

fwrite(&(pnode->item),sizeof(Item),1,fp);

应该是传递地址
[解决办法]
hi, dear friend.
i try to compile your code and print error message below:
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
test.c:29:9: error: incompatible type for argument 1 of ‘fwrite’
In file included from test.c:1:0:
/usr/include/stdio.h:717:15: note: expected ‘const void * __restrict__’ but argument is of type ‘Item’
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
size_t fwrite(const void *ptr, size_t size, size_t nmemb,
FILE *stream);
===base these info, can you understand the reason? (you pass a param pnode->item type is Item but the fwrite need accept a const void *)

to solve this problem change the code : Item item ----- Item * item


hope can help you !

yandriver8@gmail.com


[解决办法]
fwrite的原型是

size_t fwrite(const void* buffer, size_t size, size_t count, FILE* stream);

第一个参数要求传的是指针。。所以应该改为

fwrite(&pnode->item,sizeof(Item),1,fp);