The first operation we need is to get a Type_info from a C++ class pointer
or a C++ class. As already explained in the previous section, the Type_info
is a static member called, for example, 
of the C++ class. Given a C++ class T as argument, the STATIC_TYPE_INFO
macro will simply retrieve the RTTI_obj member of T. Given a C++
class pointer p (which, say, points to an actual T object),
the TYPE_INFO macro will call a virtual method via p which will
return the same RTTI_obj object (Figure 2.
Figure 2: Retrieving Type_info from C++ pointers. The TYPE_INFO
macro calls a virtual function of the pointed object which returns the
static Type_info class member of its class.
In order to do this, we need to add a static Type_info member and a
virtual method 
to each C++ class T which wishes to use RTTI operations.