Question

typedef struct
{   
   uint32 item1;
   uint32 item2;
   uint32 item3;
   uint32 item4;

   <some_other_typedef struct> *table;

} Inner_t;

typedef struct
{
   Inner_t tableA;

   Inner_t tableB;

} Outer_t;

Outer_t outer_instance =
{
   {NULL},
   {
    0,
    1,
    2,
    3,

    table_defined_somewhere_else,
   }
};

My question is how to check if tableA is NULL just like the case for outer_instance.

It tried:
if ( tmp->tableA == NULL ). I get “error: invalid operands to binary ==”

/****************************EDIT:Updated code is below *****************************/

I’ve changed the code according to bta’s suggestion but now I’m getting another error
“error: initializer element is not constant” at the line just under the NULL(at items_instance)

typedef struct
{   
   uint32 item1;
   uint32 item2;
   uint32 item3;
   uint32 item4;

} Items_t;

typedef struct
{
   Items_t *itemsA;

   Items_t *itemsB;

} Outer_t;


Items_t items_instance=
{   
   1,
   2,
   3,
   4
};

Outer_t outer_instance=
{
   NULL,
   items_instance

};

Answer 1

In the revised code, you’re setting the first field of outer_instance to NULL, but trying to set the second field to items_instance directly. Since the field has type Items_t* but items_instance has type Items_t, you’re getting a type error.

You want to set the field to the address of items_instance, so use &items_instance.