offset.cpp

Thinking in c++ 2nd edition,c++编程思想（第2版）

//: C09:Offset.cpp
// From "Thinking in C++, Volume 2", by Bruce Eckel & Chuck Allison.
// (c) 1995-2004 MindView, Inc. All Rights Reserved.
// See source code use permissions stated in the file 'License.txt',
// distributed with the code package available at www.MindView.net.
// Illustrates layout of subobjects with MI.
#include <iostream>
using namespace std;

class A { int x; };
class B { int y; };
class C : public A, public B { int z; };

int main() {
  cout << "sizeof(A) == " << sizeof(A) << endl;
  cout << "sizeof(B) == " << sizeof(B) << endl;
  cout << "sizeof(C) == " << sizeof(C) << endl;
  C c;
  cout << "&c == " << &c << endl;
  A* ap = &c;
  B* bp = &c;
  cout << "ap == " << static_cast<void*>(ap) << endl;
  cout << "bp == " << static_cast<void*>(bp) << endl;
  C* cp = static_cast<C*>(bp);
  cout << "cp == " << static_cast<void*>(cp) << endl;
  cout << "bp == cp? " << boolalpha << (bp == cp) << endl;
  cp = 0;
  bp = cp;
  cout << bp << endl;
}
/* Output:
sizeof(A) == 4
sizeof(B) == 4
sizeof(C) == 12
&c == 1245052
ap == 1245052
bp == 1245056
cp == 1245052
bp == cp? true
0
*/ ///:~