C 格式“%d”需要“int *”类型的参数，但参数 2 的类型为“unsigned int”[-Wformat=]

Question

我对这段代码有一些问题，我想编译它，但它没有编译，因为有问题。我告诉了那里的错误代码......

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

#define MAX 1000                                 
typedef struct{
    int film_id;
    char title[255];
    char description[1023];
    unsigned int release_year;
    char rental_duration;
    float rental_rate;
    unsigned char length;
    float replacement_cost;
    char rating[10];
    char last_update[30];
} RECORD_t, *RECORD;                                   

int main(){
    int i,R1;
    char R[1];
    RECORD rec = (RECORD)malloc(sizeof(RECORD_t)*MAX);  
    FILE *file = fopen("data.txt", "rb");               
    if (file == NULL) {                                 
        printf("Cannot open the file.\n");          
        exit(0);                                    
    }                                                   
    fread(rec, sizeof(RECORD_t)*MAX, 1, file);          
    fclose(file);                                       

printf("İd Numarası Giriniz : \n"); 
        scanf("%d",&R1);
        for (i=0; i<1000; i++){
            if (R1 == rec[i].film_id) {

            printf("TITLE: %s\n", rec[i].title); printf("Enter New TITLE : "); scanf("%s",rec[i].title);
            printf("DESCRIPTION: %s\n", rec[i].description); printf("Enter New Description : "); scanf("%s",rec[i].description);

// My problem is this line :-------------------
            printf("RELEASE YEAR: %d\n", rec[i].release_year); printf("Enter New RELEASE YEAR : "); scanf("%d",rec[i].release_year);
            printf("RENTAL DURATION: %d\n", rec[i].rental_duration); printf("Enter New RENTAL DURATION : "); scanf("%d",rec[i].rental_duration);
            printf("RENTAL RATE: %f\n", rec[i].rental_rate); printf("Enter New RENTAL RATE : "); scanf("%f",rec[i].rental_rate);
            printf("REPLACEMENT COST: %f\n", rec[i].replacement_cost); printf("Enter New REPLACEMENT COST : "); scanf("%f",rec[i].replacement_cost);
            printf("RATING: %s\n", rec[i].rating); printf("Enter New RATING : "); scanf("%s",rec[i].rating);
            printf("LAST UPDATE: %s\n", rec[i].last_update); printf("Enter New LAST UPDATE : "); scanf("%s",rec[i].last_update);

            }
        }

    }   


    file = fopen("data.txt", "wb");                  
    fwrite(rec, sizeof(RECORD_t)*MAX, 1, file);      
    fclose(file);                                    
    free(rec);                                       
    return 1;                                        
}

编译时只有 int 和 float 变量不起作用

warning: format ‘%d’ expects argument of type ‘int *’, but argument 2 has type ‘unsigned int’ [-Wformat=]
    printf("RELEASE YEAR: %d\n", rec[i].release_year); printf("Enter New RELEASE YEAR : "); scanf("%d",rec[i].release_year);
    ^

请帮帮我://

Answer 1

scanf 的%d 和%f 格式说明符分别期望int 和float 的地址。另外release_year 是unsigned int，所以应该使用%u 说明符，对于rental_duration，它是char，应该使用%hhd。

所以这些：

scanf("%d",rec[i].release_year);
scanf("%d",rec[i].rental_duration);
scanf("%f",rec[i].rental_rate);
scanf("%f",rec[i].replacement_cost);

应改为：

scanf("%u",&rec[i].release_year);
scanf("%hhd",&rec[i].rental_duration);
scanf("%f",&rec[i].rental_rate);
scanf("%f",&rec[i].replacement_cost);

您没有看到%s 的问题，因为数组——当传递给函数时——衰减为指向数组第一个元素的指针。

编辑：

为scanf 使用正确的大小说明符特别重要。如果您使用%d 而不是%hhd 作为char，scanf 将尝试写入一个4 字节的位置（假设int 是32 位）而不是一个字节，这将导致到未定义的行为。

来自手册页：

   h      Indicates that the conversion will be one of diouxX or n and the
          next  pointer  is a pointer to a short int or unsigned short int
          (rather than int).

   hh     As for h, but the next pointer is a pointer to a signed char  or
          unsigned char.

   l      Indicates either that the conversion will be one of diouxX or  n
          and the next pointer is a pointer to a long int or unsigned long
          int (rather than int), or that the conversion will be one of efg
          and the next pointer is a pointer to double (rather than float).
          Specifying two l characters is equivalent to L.  If used with %c
          or  %s the corresponding parameter is considered as a pointer to
          a wide character or wide character string respectively.

   L      Indicates that the conversion will be either efg  and  the  next
          pointer  is  a  pointer to long double or the conversion will be
          dioux and the next pointer is a pointer to long long.

Answer 2

调用scanf()时需要传递变量的地址

scanf("%d", &rec[i].release_year);

Answer 3

显然你的问题来自scanf("%d",rec[i].release_year);。

scanf 需要一个指向变量的指针，以便能够将读取的值存储到其中。所以一定是：scanf("%d",&(rec[i].release_year));

注意：不要将多个命令放在同一行。您的工具将您指向错误所在的行，而不是引发错误的函数。如果你把这条线分成 3 (printf+printf+scanf) 你会更快地看到问题出在哪里:)