CODEWITHSUNDEEP
clinkerheader-files
Amr Ayman
Amr Ayman

Reputation: 1159

Incomplete Type with header

I have a header file:

Location.h

#ifndef LOCATION_H
#define LOCATION_H

#define MAX_X_GRID (3)
#define MAX_Y_GRID (3)

typedef struct _location Location;

extern Location *Location_create();
extern void Location_destroy(Location *);

#endif /* LOCATION_H */

.. a soure file:

Location.c

#include <stdlib.h>
#include "Location.h"

#define VALID_LOCATION_CODE (245)
#define _location_check(l) \
    if ( l == NULL || l->_Valid != VALID_LOCATION_CODE ) \
        abort();

struct _location
{
    int x;
    int y;
    int _Valid;
};

struct _location *Location_create(const int x, const int y)
{
    if (x > MAX_X_GRID || y > MAX_Y_GRID)
        return NULL;

    struct _location *l = malloc(sizeof(struct _location));
    if (l == NULL)
        return NULL;
    l->x = x;
    l->y = y;
    l->_Valid = VALID_LOCATION_CODE;
    return l;
}

void Location_destroy(struct _location *l)
{
    _location_check(l);
    free(l);
}

.. and I am testing the code like that:

test.c

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

int main(int argc, char const *argv[])
{
    Location *l = Location_create(1, 2);
    printf("x: %d, y: %d\n", l->x, l->y); /* line 6 */
    Location_destroy(l);
    return 0;
}

When I compile the program with this command:

gcc test.c -o test -Wall

I get these errors:

test.c:6:27: error: trying to dereference a pointer of incomplete type

// line 6

test.c:6:33: error: trying to dereference a pointer of incomplete type

// line 6

From the errors, it seems that gcc is not aware of the header file I included.

What can I do to fix that ?

Upvotes: 0

Views: 901

Answers (2)

user58697
user58697

Reputation: 7923

Location.h doesn't disclose the contents of the struct _location (type is incomplete), so while compiling test.c gcc has no clue what l->x and l->y are.

Upvotes: 2

David C. Rankin
David C. Rankin

Reputation: 84642

You need to move the struct and function declarations (not definitions) into the header. E.g. move the following into the header file:

#ifndef LOCATION_H
#define LOCATION_H

#define MAX_X_GRID (3)
#define MAX_Y_GRID (3)

typedef struct _location Location;

struct _location
{
    int x;
    int y;
    int _Valid;
};

struct _location *Location_create(const int x, const int y);
void Location_destroy(struct _location *l);

#endif /* LOCATION_H */

Upvotes: 0

Related Questions