51-c++ Object Model analysis (bottom)

Inherit object model

? The inner class of the C + + compiler can be understood as a struct

? Subclasses are the new members of the parent class that are superimposed on the child class.

On the model of "sample Code" inheriting object

1#include <iostream>2#include <string>3 4 using namespacestd;5 6 classDemo {7 protected:8     intmi;9     intMJ;Ten  Public: One     Virtual voidprint () { Acout <<"mi ="<< mi <<", " -<<"MJ ="<< MJ <<Endl; -     } the }; -  - classDerived: PublicDemo { -     intMk; +  Public: -Derived (intIintJintk) { +Mi =i; AMJ =J; atmk =K; -     } -  -     voidprint () { -cout <<"mi ="<< mi <<", " -<<"MJ ="<< MJ <<", " in<<"mk ="<< Mk <<Endl; -     } to }; +  - //proving that the derived memory arrangement is the same as the test class the structTest { *     void*p; $     intmi;Panax Notoginseng     intMJ; -     intMk; the }; +  A intMainintargcConst Char*argv[]) { thecout <<"sizeof (Demo) ="<<sizeof(Demo) <<Endl; +cout <<"sizeof (Derived) ="<<sizeof(Derived) <<Endl; -  $Derived D (1,2,3); $test* p = reinterpret_cast<test*> (&d); -  -cout <<"before changing ..."<<Endl; the  - d.print ();Wuyi  theP->mi =Ten; -P-&GT;MJ = -; WuP-&GT;MK = -; -  Aboutcout <<"After changing ..."<<Endl; $  - d.print (); -  -     return 0; A}

Polymorphic Object Model

C + + polymorphism implementation principle:

? When a virtual function is declared in a class, the compiler generates a virtual function table in the class

? A virtual function table is a data structure that stores the address of a member function

? Virtual function tables are automatically generated and maintained by the compiler.

? The virtual member function is placed in the virtual function table by the compiler

? When there is a virtual function table, there is a pointer to the virtual function table in each object

void int v) {    P-and add (v);}

Does the compiler confirm that add () is a virtual function?

• The yes--> compiler looks for the address of the Add () in the virtual function table that the object vptr points to
• No--the compiler can directly determine the address of the member function being called

51-c++ Object Model analysis (bottom)