offset.cpp

来自「C语言数值算法程序大全（第二版）,课本文件」· C++ 代码 · 共 49 行

//: C09:Offset.cpp
// From "Thinking in C++, 2nd Edition, Volume 2"
// by Bruce Eckel & Chuck Allison, (c) 2003 MindView, Inc.
// Available at www.BruceEckel.com.
// 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
*/ ///:~