Thread: struct declarations in header files

I am currently experiencing the error:

file1.c:51: error: storage size of 'var' isn't known

I am thinking that it is because I've defined a struct in a .c file, and it has no corresponding declaration in its header file. I've got file1.c, which is the program I am trying to declare a struct variable in (on line 51, as indicated by the error above), file2.c, which contains the struct definition, and file2.h which contains declarations for other functions in file2.c. Line 51 in file1.c looks like this:

Code:

struct my_struct var;

So, I understand that file1.c really has no way of knowing what my_struct is, because it only includes a statement #include "file2.h". It seems like I'm missing a struct declaration in file2.h. How do I do this? By the way, the structure definition in file2.c looks like this:

Code:

struct my_struct {
   char first_name[20];
   char last_name[20];
};

Thanks in advance!

You can include the c file to another C file.
Ex:
#include "file2.c"

But you should not use main function in that file2.c. If you have main function in file2.c while including this it will give error.

Otherwise you can maintain the common header file for that programs. In that header file you can define the structure.

Would you mind providing the structure definition for the header file in this example? Thanks, much appreciated!

I think your suspection is right ,
You must be defined that struct in a header file , then you can include in the normal .c file.
in that C file you can create a structure variable

Code:

 
Filename : struct.h 

 struct my_struct {
           char first_name[20];
              char last_name[20];
};

Filename : s1.c 
#include<stdio.h> 
#include "struct.h"

main()
{

struct my_struct var1 ;  // Works perfectly 

}

No matter how many files you are using , you should simply include
the header file.

Now I am having the following issue:

error: incompatible types in assignment

my file1.c looks like this:

Code:

#include <stdio.h>
#include "file2.h"

int main() {
	struct my_struct new_struct;
	new_struct = create_my_struct();
	printf("%s %s", new_struct.first_name, new_struct.last_name);
	return 0;
}

and, my file2.c looks like this

Code:

#include <string.h>

struct my_struct create_my_struct() {
	struct my_struct ms;

	strcpy(ms.first_name, "john");
	strcpy(ms.last_name, "smith");

	return ms;
};

The issue relates to line6 in file1.c (new_struct = create_my_struct();). These both seem to be of the same type (file1 declares a variable of type my_struct, and file2 returns a variable of type my_struct). Any idea what the issue might be?

You're right! Thanks again! Alright, too many ridiculous mistakes...time for sleep.