# include 

using namespace std; 

Class A 
{
Public: 
Virtual void print () {cout<" "This is a. & lt; }; 

Class B: public A 
{
Public: 
(B) {data=https://bbs.csdn.net/topics/2; } 
Virtual void printB () {cout<" This is b. "& lt; The int data; 
}; 

Int main () 
{
A a; 
A, b. 
A * c=new A (); 
B, d; 
B e; 
A * f=new B (); 
B * g=new B (); 

return 0; 
} 

Code as above, and then use the GDB debugging results are as follows:

 
29 return 0; 
(GDB) print a 
$1={_vptr. A=0 x400bc0} 
(GDB) print b 
$2={_vptr. A=0 x400bc0} 
(GDB) print * c 
$3={_vptr. A=0 x400bc0} 
(GDB) print d 
$4={& lt; A>={_vptr. A=0 x400c10}, data=https://bbs.csdn.net/topics/2} 
(GDB) print e 
$5={& lt; A>={_vptr. A=0 x400c10}, data=https://bbs.csdn.net/topics/2} 
(GDB) print * f 
$6={_vptr. A=0 x400c10} 
(GDB) print * g 
$7={& lt; A>={_vptr. A=0 x400c10}, data=https://bbs.csdn.net/topics/2} 
The quit (GDB) 
A was debugging session is active. 

Is not A virtual table is followed by an object, why defines the different objects, they use the same virtual pointer table (of the same type of object _vptr. A at the same address), A great god explain it in detail,