基於結構的程序，鏈接程序和多個定義？

Question

這是我得到的文件，被告知不要更改二者之一。 函數的規范在標頭中，並且main.c是用於測試代碼的shell：

date.h：

#ifndef _DateH_
#define _DateH_

typedef struct {
int month;
int day;
int year;
} date;

int is_leap_year(int the_year);

int days_in_month(int month,int leap_year);
// Recommendation: use switch statement


void input_date(date *dp);  // User input of form mm/dd/yyyy
                        // where mm, dd and yyy are integers
                        // NO PROMPT  JUST INPUT

void print_date(date d);    // Output format same as input_date's input format

int day_of_year(date d);    // Number of days since beginning of year
                        // January 1 is day 1 (not 0)

int compare_dates(date d1, date d2);
// Returns -1 if d1 earlier than d2, 0 if same date, +1 if d1 after d2

void check_age_and_birthday(date birthdate, date today);
// Output: "You are __ years old and this is your birthday\n"
//      or "You are __ years old and this is not your birthday\n"

void submit_status(date start, date end, date submit);
// Prints ""Submission not accepted - too early\n" if submit < start;
//        "Submission not accepted too - late\n" if end < submit;
//        "Submission accepted\n"  otherwise.
#endif

// Note: A year is a leap year if and only if it is divisible by 4
// and, if it is divisible by 100, it is also divisible by 400.

main.c：

#include "date.h"
#include <stdio.h>

int main()
{
  date d,bdate,today,start,end,submit;

  printf("Enter a date: ");
  input_date(&d);

  printf("\n");
  print_date(d);
  printf(" is day %d of year %d, which is ",day_of_year(d),d.year);
  if (!is_leap_year(d.year))
    printf("not ");
  printf("a leap year\n\n");

  printf("Enter your birthdate: ");
  input_date(&bdate);

  printf("Enter today's date: ");
  input_date(&today);

  printf("\n");
  check_age_and_birthday(bdate,today);

  printf("\nEnter the start date: ");
  input_date(&start);

  printf("Enter the end date: ");
  input_date(&end);

  printf("Enter the date submitted: ");
  input_date(&submit);

  printf("\n\n");
  submit_status(start,end,submit);

  return 0;
}

date.c：

#include "date.h"

int is_leap_year(int the_year)
{
   if (the_year % 4 == 0) {
                if (the_year % 100 == 0) {
                        if (the_year % 400 == 0) {
                                return (1);
                        }
                        else return (0);
                }
                else return (1);
        }
        else return (0);
}

int days_in_month(int month, int leap_year)
{
        switch (month) {
                case 1: {
                        return (31);
                        break;
                }
                case 2: {
                        if (leap_year) return (29);
                        else return (28);
                        break;
                }
                case 3: {
                        return (31);
                        break;
                }
                case 4: {      
                        return (30);
                        break;
                }
                case 5: {
                        return (31);
                        break;
                }
                case 6: {
                        return (30);
                        break;
                }
                case 7: {
                        return (31);
                        break;
                }
                case 8: {
                        return (31);
                        break;
                }
                case 9: {      
                        return (30);
                        break;
                }
                case 10: {
                        return (31);
                        break;
                }
                case 11: {
                        return (30);
                        break;
                }
                case 12: {
                        return (31);
                        break;
                }
        }              
}

void input_date(date *dp)
{
        do
        {
             scanf("%d/%d/%d", dp->month, dp->day, dp->year);
        }
        while
             (dp->day > days_in_month(dp->month, is_leap_year(dp->year)) || dp->day < 1);
}

void print_date(date d)
{
        printf("%d/%d/%d", d.month, d.day, d.year);
}


int day_of_year(date d)
{
        int day_sum = 0;
        int i;

        if (is_leap_year(d.year))
        {
          for (i = 1; i < d.month; i++)
              {
              day_sum = day_sum + days_in_month(i, 1);
              }

        }
        else
        {
             for (i = 1; i < d.month; i++)
             {
                day_sum += days_in_month(i, 0);
             }
        }

         day_sum += d.day;

         return (day_sum);
}

void check_age_and_birthday(date birthdate, date today)
{
        int age;

        if (today.month > birthdate.month)
        {
                age = today.year - birthdate.year;
        }
        if (today.month < birthdate.month)
        {
                age = (today.year - birthdate.year) - 1;
        }
        if (today.month == birthdate.month)
        {
                if ((today.day > birthdate.day) || (today.day == birthdate.day)) {
                        age = today.year - birthdate.year;
                }
                if (today.day < birthdate.day) {
                        age = (today.year - birthdate.year) - 1;
                }
        }

        if (!compare_dates(birthdate, today))
        {
                printf ("You are %d years old and this is your birthday\n", age);
        }
        else
        {
                printf ("You are %d years old and this is not your birthday\n", age);
        }
}

 int compare_dates(date d1, date d2)
{
        if (d1.year > d2.year)
        {
                return (1);
        }
        if (d1.year < d2.year)
        {
                return (-1);
        }
        if (d1.year == d2.year)
        {
                if (d1.month > d2.month)
                {
                        return (1);
                }
                if (d1.month < d2.month)
                {
                        return (-1);
                }
                if (d1.month == d2.month)
                {
                        if (d1.day > d2.day)
                        {
                                return (1);
                        }
                        if (d1.day < d2.day)
                        {
                                return (-1);
                        }
                        if (d1.day == d2.day)
                        {
                                return (0);
                        }
                }
        }

 }

void submit_status(date start, date end, date submit)
{
        if (compare_dates(submit, start) == -1)
        {
                printf("Submission not accepted - too early\n");
        }
        if (compare_dates(submit, end) == 1)
        {
                printf("Submission not accepted - too late\n");
        }
        if ((compare_dates(submit, start) == 1) && (compare_dates(submit, end) == -1))
        {
                printf("Submission accepted\n");
        }

}

當我將它們放入“控制台應用程序”項目並進行構建時，出現錯誤：

[Linker error] undefined reference to `submit_status'  
ld returned 1 exit status  
[Build Error] [DateStruct.exe] Error 1

如果我在單獨的選項卡中運行它們，而未創建任何項目，則會得到：

mangled line number section.  
[Linker error] undefined reference to `WinMain@16'  
ld returned 1 exit status

我為此使用Dev-C ++。

Answer 1

輸入日期時您的程序崩潰，因為您將dp->month ， dp->day和dp->year的值傳遞給scanf() 。 scanf()需要一個指針來存儲結果； 在C中，整數看起來像一個指針，因此它很樂意嘗試將dp->month的單位化值解釋為指針，並由於無法在其中寫入而崩潰。

您想改用&dp->month等。

我建議在啟用所有警告的情況下進行編譯（我不知道Dev-C ++，但是GCC標志是-Wall -Wextra ）； 我還建議您處理有關錯誤的警告，以-Werror您不會意外地使用-Werror忽略它們。 如果我在啟用警告的情況下進行編譯，則GCC會告訴我有關該問題的信息：

cc -Wall -Werror -Wextra    struct.c   -o struct
struct.c: In function ‘main’:
struct.c:13:3: error: format ‘%d’ expects argument of type ‘int *’, but argument 2 has type ‘int’ [-Werror=format]
struct.c:13:3: error: format ‘%d’ expects argument of type ‘int *’, but argument 3 has type ‘int’ [-Werror=format]
cc1: all warnings being treated as errors

這個示例錯誤也來自我寫的一個非常快速的測試文件。 在調試問題時，如果嘗試創建簡短的，獨立的示例問題，並詢問是否遇到問題，它確實會有所幫助。 您發布的代碼有很多無關緊要的地方。 幾個頭文件，您從未真正使用過的函數，等等。 將您的代碼簡化為一個最小的問題示例，可以幫助您自己找到問題，或者失敗了，請提供一個示例，讓其他人更輕松地查看和查看問題，而無需花很多時間。

這是一個演示該問題的最小示例：

#include <stdio.h>                                                                                      

struct foo {                                                                                            
  int bar;                                                                                              
  int baz;                                                                                              
};                                                                                                      

int main() {                                                                                            
  struct foo x, *px;                                                                                    
  px = &x;                                                                                              

  printf("Enter bar and baz: \n");
  scanf("%d %d", px->bar, px->baz);

  printf("Got: %d %d\n", px->bar, px->baz);

  return 0;
}

以及解決方法：

#include <stdio.h>                                                                                      

struct foo {                                                                                            
  int bar;                                                                                              
  int baz;                                                                                              
};                                                                                                      

int main() {                                                                                            
  struct foo x, *px;                                                                                    
  px = &x;                                                                                              

  printf("Enter bar and baz: \n");
  scanf("%d %d", &px->bar, &px->baz);

  printf("Got: %d %d\n", px->bar, px->baz);

  return 0;
}