Forward declaration of typedef structs in GBDK C

Question

I'm using GBDK C to create a Game for the original Game Boy, and I have run in to a little problem. Each room in my game needs to have different portals, but each portal needs to reference a room. Here is a cut-back version of the code:

typedef struct {
    Portal portals[10];
} Room;

typedef struct {
    Room *destinationRoom;
} Portal;

Any suggestions on how to achieve this? I tried adding a forward declaration of struct Portal; to the top of the file but it didn't help.

---

Using the following code:

typedef struct Room Room;
typedef struct Portal Portal;

struct Room {
    Portal portals[10];
};

struct Portal {
    Room *destinationRoom;
};

Gives me this error:

parse error: token -> 'Room' ; column 11
*** Error in `/opt/gbdk/bin/sdcc': munmap_chunk(): invalid pointer: 0xbfe3b651 ***

Answer 1

Reorder the definitions and write a forward declaration for the Room and Portal types:

typedef struct Room Room;
typedef struct Portal Portal;

struct Portal {
    Room *destinationRoom;
};

struct Room {
    Portal portals[10];
};

Note that I separated the typedef Portal from the actual struct Portal definition for consistency, even though it is not strictly necessary.

Also note that this style is compatible with C++, where the typedef is implicit but can be written explicitly this way, or with a simple forward declaration like struct Room;

If for some reason you cannot use the same identifier for the struct tag and the typedef, you should declare the structures this way:

typedef struct Room_s Room;
typedef struct Portal_s Portal;

struct Portal_s {
    Room *destinationRoom;
};

struct Room_s {
    Portal portals[10];
};