'class1' : illegal member initialization: 'class2' is not a base or member
A class in an initialization list was not a base class or member.
Only a member or base class can be in the initialization list for a class or structure.
The following is an example of this error:
class A
{
public:
int i;
A( int ia ) : B( i ) {}; // error, B is not a member of A
};