Structs that refer to each other

Question

I want to have two structs that can contain each other. Here is an example:

struct a {   struct b bb; };  struct b {   struct a aa; }; 

But this code doesn't compile. gcc says:

test.c:3: error: field ‘bb’ has incomplete type 

Is there a way to achieve this?

Answer 1

How is that supposed to work? a would contain b, which would contain a, which would contain b, etc...

I suppose you want to use a pointer instead?

struct b;  struct a {   struct b *bb; };  struct b {   struct a *aa; }; 

Even that though is bad coding style - circular dependencies should be avoided if possible.

Answer 2

struct a; struct b;  struct a{    struct b *bb; };  struct b{    struct a *aa; }; 

Most of the header file declare the structure before defining its members. Structure definition will be defined in somewhere else.