Question

The objective is to build a “infinite” tree using dynamic arrays.

items[3]
- MENUITEM
  - items[2]
    - MENUITEM
      -items[0]
    - MENUITEM
      - items[0]
- MENUITEM
  - items[0]
- MENUITEM
  - items[2]
    - MENUITEM
      - items[0]
    - MENUITEM
      - items[0]

I define the structure:

typedef struct MENUITEM {
    char id, count;
    char *description;
};

And I can allocated items dynamically with:

char count;
MENUITEM items[], *items_ptr;

count++;
realloc( items_ptr, count * sizeof(struct MENUITEM) );

The problem is that inside the structure I cannot assign again the structure itself like:

typedef struct MENUITEM {
    char id, count;
    char *description;

    MENUITEM items[], *items_ptr;
};

The compiler outputs: error: field ‘items’ has incomplete type; what am I doing wrong here ?
Thanks for any help provided.

Answer 1

You need to use struct MENUITEM *items_ptr;. Note the use of the word struct.

Why do you have MENUITEM items[]? It’s not used for anything.

Do this instead:

typedef struct MENUITEM {
    char id, count;
    char *description;

    struct MENUITEM *items;
} MENUITEM;

void foo() {
    MENUITEM *root = (MENUITEM*)malloc(sizeof(MENUITEM));

    root->id = 87;
    root->count = 5;

    root->items = (MENUITEM*)malloc(sizeof(MENUITEM)*root->count);
}