C + +-derived classes cast to base class

derived classes cast to base class

This address: http://blog.csdn.net/caroline_wendy/article/details/24268821

in the case of polymorphic use, A pointer to a derived class or a reference to a pointer or reference that can be converted to a base class, that is, pointer to base class can point to base class part of a derived class ;

base* B = derived* D;

B and D point to the content is equal , b = = d, because there is an implicit conversion between b = = (base*) D;

the addresses of B and d are different int (b)! = Int (d), because B points to the base class part of D, and D points to the complete derived class;

But assuming the stealth conversion , int (b)! = Int ((base*) d), the address is the same.

The code is as follows:

/* * test.cpp * *  Created on:2014.04.21 *      author:spike *//*eclipse CDT, gcc 4.8.1*/#include <iostream>clas s A {int m_na;}; Class B {int m_nb;}; Class C:public A, public B {int m_nc;}; int main (void) {c* pc = new C; b* PB = pc;if (PC = pb) {std::cout << "equal" << Std::endl;} else {std::cout << "not Equal" << St D::endl;} if (int (PC) = = Int (pb)) {std::cout << "equal" << Std::endl;} else {std::cout << "not equal" << std :: Endl;}  if (int (PC) = = Int ((c*) pb) {std::cout << "equal" << Std::endl;} else {std::cout << "not Equal" << Std::endl;} return 0;}

Output:

Equalnot equalequal

C + +-derived classes cast to base class