what wrong with it?解决办法

what wrong with it?C/C++ codeclass Foo{Bar b}class Bar{Foo a}[解决办法]C/C++ codeclass Barclas

what wrong with it?

C/C++ code
class Foo{    Bar b;};class Bar{    Foo a;};


[解决办法]
C/C++ code
class Bar;class Foo{    Bar *b;};class Bar{    Foo a;};