Various inherited memory layouts (virtual tables)

Virtual inheritance

1. Memory layout: Base1,base2 each has its own virtual table, because its own virtual function in the class.

#include <iostream>using namespace std;typedef void (*fun) (); class base{public:virtual &NBSP;VOID&NBSP;FUN1 () {cout <<  "base::fun1 ()" &NBSP;&LT;&LT;&NBSP;ENDL;} public:int _b;}; CLASS&NBSP;BASE1&NBSP;:VIRTUAL&NBSP;PUBLIC&NBSP;BASE{PUBLIC:VIRTUAL&NBSP;VOID&NBSP;FUN1 () {cout <<   "base1::fun1 ()" &NBSP;&LT;&LT;&NBSP;ENDL;} VIRTUAL&NBSP;VOID&NBSP;FUN3 () {}public:int _b1;}; CLASS&NBSP;BASE2&NBSP;:VIRTUAL&NBSP;PUBLIC&NBSP;BASE{PUBLIC:VIRTUAL&NBSP;VOID&NBSP;FUN1 () {cout <<   "base2::fun1 ()" &NBSP;&LT;&LT;&NBSP;ENDL;} Virtual void fun2 () {}public:int _b2;}; class derive :p ublic base1, public base2{public:virtual void fun1 () {cout  <<  "derive::fun1 ()" &NBSP;&LT;&LT;&NBSP;ENDL;} public:int _d;}; Void printvtable (int *ptr) {for  (int i = 0; ptr[i] != 0; ++i) {fun f =  (Fun) ptr[i];f ();}} Int main () {DERIVE&NBsp;b1;b1._b1 = 2;b1. Base1::_b = 1;b1._b2 = 3;b1._d = 4;/*int *p1= (int *) (* (int*) &AMP;B1); Printvtable (p1), cout<<sizeof (BASE1) <<endl;int *p2= (int*) (* (int*) ((int) &b1+sizeof (BASE1))) ; Printvtable (p2); */system ("pause"); return 0;}

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2. There is a virtual function in the subclass, so the virtual table pointer must be created in the parent class

Class Base1:virtual Public Base

{

Public

virtual void fun1 ()

{

cout << "base1::fun1 ()" << Endl;

}

Public

int _b1;

};

Class Base2:virtual Public Base

{

Public

virtual void fun1 ()

{

cout << "base2::fun1 ()" << Endl;

}

Public

int _b2;

};

Class Derive:p ublic Base1, public Base2

{

Public

virtual void fun1 ()

{

cout << "derive::fun1 ()" << Endl;

}

virtual void fun2 ()

{

}

Public

int _d;

};

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3. No virtual function in parent class, create virtual table pointer in child class

Class Base

{

Public

Public

int _b;

};

Class Base1:virtual Public Base

{

Public

virtual void fun1 ()

{

cout << "base1::fun1 ()" << Endl;

}

Public

int _b1;

};

Class Base2:virtual Public Base

{

Public

virtual void fun1 ()

{

cout << "base2::fun1 ()" << Endl;

}

Public

int _b2;

};

Class Derive:p ublic Base1, public Base2

{

Public

virtual void fun1 ()

{

cout << "derive::fun1 ()" << Endl;

}

virtual void fun2 ()

{

}

Public

int _d;

};

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This article is from the "Small Stop" blog, please be sure to keep this source http://10541556.blog.51cto.com/10531556/1722157

Various inherited memory layouts (virtual tables)