How to use structure from one c file in another [duplicate] - c

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How to use a defined struct from another source file?
(7 answers)
Closed 5 years ago.
is it posibble in C, that you define a structure in one .c file, but use it in another?
Basically, I would like to use my List that I have already created in another program. But I would like to use diffrent structures.
I've 3 files:
main.c -- another program, where I want to use the list
list.c -- code of the list
head.h -- header to bind them
In main.c:
#include <stdio.h>
#include <stdlib.h>
typedef struct cell{
int x;
cell next;
}TCell;
typedef struct{
TCell first;
int lenght;
}List;
#include "head.h"
int main()
{
TCell *c
c->x = 5;
List *l;
init(l);
add(l,c)
c = get();
return 0;
}
head.h:
#ifndef HEAD_H_
#define HEAD_H_
void init(List *l);
void add(List *l, TCell *c);
TCell get();
(...)
#endif
list.c
#include <stdio.h>
#include <stdlib.h>
#include "head.h"
typedef struct{
TCell first;
int lenght;
}List;
void init(List *l){ (...) }
void add(List *l, TCell *c) { (...) }
TCell get() { (...) }
(...)
But when i try to compile it, it doesn't work, because it is missing the TCell in head.h and list.c, and the List in head.h
So, is there a possibility to have just one definition of TCell in the main.c, so whenever i change its inner variables, it will still work?

Answer 1

Make this your head.h:
#ifndef HEAD_H_
#define HEAD_H_
typedef struct cell
{
int x;
cell next;
} TCell;
typedef struct
{
TCell first;
int lenght;
} List;
void init(List *l);
void add(List *l, TCell *c);
TCell get();
...
#endif
And remove the typedef of List and TCell from list.c and main.c, because you only need to define a type once.
Header files are meant to contain your shared type definitions.
Here's an entry of the famous C-FAQ that may help. I advise you to read through this whole FAQ it will teach you a lot of things about C and will save you a lot of time.