(C++ Object Model): Adjust this pointer

table of Contents

this pointer adjustment

explore

Schematic diagram

to sum up

---

this pointer adjustment

explore

#include <iostream>
using namespace std;

class A {
public:
	int a;
	A()
	{
		printf("A::A()的this指针是：%p!\n", this);
	}
	void funcA()
	{
		printf("A::funcA()的this指针是：%p!\n", this);
	}
};

class B {
public:
	int b;
	B()
	{
		printf("B::B()的this指针是：%p!\n", this);
	}
	void funcB()
	{
		printf("B::funcB()的this指针是：%p!\n", this);
	}
};

class C : public A, public B
{
public:
	int c;
	C()
	{
		printf("C::C()的this指针是：%p!\n", this);
	}
	void funcC()
	{
		printf("C::funcC()的this指针是：%p!\n", this);
	}

	void funcB()
	{
		printf("C::funcB()的this指针是：%p!\n", this);
	}
};


int main()
{
	//this指针调整：多重继承
	cout << sizeof(A) << endl;
	cout << sizeof(B) << endl;
	cout << sizeof(C) << endl;

	C myc;
	myc.funcA();
	myc.funcB(); //已经被子类C覆盖了
	myc.B::funcB();
	myc.funcC();
	return 1;
}

• Output result

Schematic diagram

to sum up

• Derived class objects contain sub-objects of the base class .
• If the derived class only inherits from one base class , then the address of the derived class object is the same as the address of the base class sub-object .
• But if the derived class object inherits multiple base classes at the same time, then we must pay attention to :
  • The start address of the first base class object is the same as the start address of the derived class object .
  • What is the difference between the start address of these subsequent base class sub-objects and the start address of derived class objects?
    • Then you have to get rid of the memory space occupied by the previous base class sub-objects .
• Summary: You member function calls which subclass , the this pointer will be automatically adjusted to the compiler target memory layout of the start address should subclass object to that ;