Why can't I define nested (loop) statements in a struct in C language?

It's a problem if you have a chicken or an egg. So we wantCodeCompilation is impossible:

Typedef struct a;
Typedef struct B;

Struct
{
B BB;
Int I;
};
Struct B
{
A aa;
Int I;
};

No way. It seems that only pointers are used.

# Include <stdio. h>
Typedef struct a;
Typedef struct B;
Struct
{
B * BB;
Int I;
};
Struct B
{
A * AA;
Int I;
};

Int
Main (void)
{
A A1;
B B1;
A1. I = 1;
B1. I = 2;

A1.bb = & B1;
B1.aa = & A1;

Printf ("I: % d/N", a1.bb-> I );
Printf ("I: % d/N", b1.aa-> I );
}

So the code can work.