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.