CODEWITHSUNDEEP
cstructheader-files
zahid kamil
zahid kamil

Reputation: 165

Why is my struct (declared in the header file) not being recognized in the c file in gcc compile?

I am unable to compile the following code because my gcc compiler (MSYS2 12.1.0) is not recognizing the struct that I have created in my header file diffDates.h.

Below is the header file

#ifndef DIFFDates_H
#define DIFFDates_H

int getDifference(Date dt1, Date dt2);

// A date has day 'd', month 'm' and year 'y'
struct Date {
    int d, m, y;
};

#endif

Below is my main file makefiles.c

#include <stdio.h>
#include <string.h>
#include "diffDates.h"

int main()
{
    char str_start[10];
    char str_end[10];
    printf("Please enter the start date in dd.mm.yy: ");
    scanf("%s", str_start);
    printf("\nPlease enter the end date in dd.mm.yy:");
    scanf("%s", str_end);

    return 0;
}

Below is the output from the GCC compiler

gcc makefiles.c -o makefiles     
In file included from makefiles.c:7:
diffDates.h:4:19: error: unknown type name 'Date'
    4 | int getDifference(Date dt1, Date dt2);
      |                   ^~~~
diffDates.h:4:29: error: unknown type name 'Date'
    4 | int getDifference(Date dt1, Date dt2);
      |                             ^~~~
diffDates.h:19:20: error: unknown type name 'Date'
   19 | int countLeapYears(Date d)
      |                    ^~~~
diffDates.h:40:19: error: unknown type name 'Date'
   40 | int getDifference(Date dt1, Date dt2)
      |                   ^~~~
diffDates.h:40:29: error: unknown type name 'Date'
   40 | int getDifference(Date dt1, Date dt2)
      |

I would like to know what is wrong because I can include functions in the main file but structs are not defined for some reason.

Upvotes: 2

Views: 931

Answers (1)

abdo Salm
abdo Salm

Reputation: 1841

first of all, in C. to define a struct and declare an instance of that struct, you either type:

struct Date {
    int d, m, y;
};

int getDifference(struct Date dt1, struct Date dt2);

Or

typedef struct Date {
    int d, m, y;
}Date;

int getDifference(Date dt1, Date dt2);

second of all, the line :

int getDifference(Date dt1, Date dt2);

must come after :

typedef struct Date {
    int d, m, y;
}Date;

not before it, as during compilation. when the compiler reaches that line int getDifference(Date dt1, Date dt2); , it has no information about the user data type called Date .

so edit the header file to be :

#ifndef DIFFDates_H
#define DIFFDates_H

// A date has day 'd', month 'm' and year 'y'
typedef struct Date {
    int d, m, y;
}Date;

int getDifference(Date dt1, Date dt2);

#endif

Upvotes: 2

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