继承体系中 destructor 的执行次序

《深度探索C++对象模型》P.233 L.-2: 

一个由程序员定义的 destructor 被扩展的方式类似 constructor 被扩展的方式，但顺序相反：

1. 如果 object 内带一个 vptr，那么首先重设 (reset) 相关的 virtual table；
    If the object contains a vptr, it is reset to the virtual table associated with the class.

2. destructor 的函数本身现在被执行，也就是说 vptr 会在程序员的码执行前被重设 (reset)；
    The body of the destructor is then executed; that is, the vptr is reset prior to evaluating the user-supplied code.

3. 如果 class 拥有 member class objects，而后者拥有 destructors，那么它们会以其声明顺序的相反顺序被调用；
    If the class has member class objects with destructors, these are invoked in the reverse order of their declaration.

4. 如果有任何直接的（上一层）nonvirtual base classes 拥有 destructors，它们会以其声明顺序的相反顺序被调用；
    If there are any immediate nonvirtual base classes with destructors, these are invoked in the reverse order of their declaration.

5. 如果有任何 virtual base classes 拥有 destructor，而当前讨论的这个 class 是最尾端 (most-derived) 的 class，那么它们会以其原来的构造顺序的相反顺序被调用。
    If there are any virtual base classes with destructors and this class represents the most-derived class, these are invoked in the reverse order of their original construction.

侯捷认为正确的顺序应该是 2、3、1、4、5。即：

1. destructor 的函数本身首先被执行；

2. 如果 class 拥有 member class objects，而后者拥有 destructors，那么它们会以其声明顺序的相反顺序被调用；

3. 如果 object 内带一个 vptr，则现在被重新设定，指向适当之 base class 的 virtual table；

4. 如果有任何直接的（上一层）nonvirtual base classes 拥有 destructors，它们会以其声明顺序的相反顺序被调用；

5. 如果有任何 virtual base classes 拥有 destructor，而当前讨论的这个 class 是最尾端 (most-derived) 的 class，那么它们会以其原来的构造顺序的相反顺序被调用。

从下面测试代码的输出，可以看出，在 VC++ 2005 编译器中，侯捷的说法是正确的。

测试代码：
// VC++ 2005 #include <stdio.h> class Derived; Derived* g_pDerived = NULL; Derived* g_pDerived2 = NULL; class Base_Base { public: virtual ~Base_Base() { printf("/nBase_Base destructor/n"); vfunc(); } virtual void vfunc() { printf("Base_Base::vfunc/n"); } }; class Base: public virtual Base_Base { public: virtual ~Base() { printf("/nBase destructor/n"); vfunc(); } virtual void vfunc() { printf("Base::vfunc/n"); } }; class Base2_Base { public: virtual ~Base2_Base() { printf("/nBase2_Base destructor/n"); vfunc(); } virtual void vfunc() { printf("Base2_Base::vfunc/n"); } }; class Base2: public Base2_Base { public: virtual ~Base2() { printf("/nBase2 destructor/n"); vfunc(); } virtual void vfunc() { printf("Base2::vfunc/n"); } }; class Base3_Base { public: virtual ~Base3_Base() { printf("/nBase3_Base destructor/n"); vfunc(); } virtual void vfunc() { printf("Base3_Base::vfunc/n"); } }; class Base3: public Base3_Base { public: virtual ~Base3() { printf("/nBase3 destructor/n"); vfunc(); } virtual void vfunc() { printf("Base3::vfunc/n"); } }; class Base4_Base { public: virtual ~Base4_Base() { printf("/nBase4_Base destructor/n"); vfunc(); } virtual void vfunc() { printf("Base4_Base::vfunc/n"); } }; class Base4: virtual public Base4_Base { public: virtual ~Base4() { printf("/nBase4 destructor/n"); vfunc(); } virtual void vfunc() { printf("Base4::vfunc/n"); } }; class Base5_Base { public: virtual ~Base5_Base() { printf("/nBase5_Base destructor/n"); vfunc(); } virtual void vfunc() { printf("Base5_Base::vfunc/n"); } }; class Base5: virtual public Base5_Base { public: virtual ~Base5() { printf("/nBase5 destructor/n"); vfunc(); } virtual void vfunc() { printf("Base5::vfunc/n"); } }; class MemberClass { public: virtual ~MemberClass(); private: Derived* _pDerived; }; class MemberClass2 { public: virtual ~MemberClass2(); private: Derived* _pDerived; }; class Derived : virtual public Base , public Base2 , virtual public Base3 , virtual public Base5 , public Base4 { public: virtual ~Derived(); virtual void vfunc(); private: MemberClass mc; MemberClass2 mc2; }; Derived::~Derived() { printf("Derived destructor/n"); vfunc(); } void Derived::vfunc() { printf("Derived::vfunc/n"); } MemberClass::~MemberClass() { printf("/nMemberClass destructor/n"); _pDerived = new Derived; g_pDerived = _pDerived; _pDerived->vfunc(); } MemberClass2::~MemberClass2() { printf("/nMemberClass2 destructor/n"); _pDerived = new Derived; g_pDerived2 = _pDerived; _pDerived->vfunc(); } int main() { Derived oDerived; delete g_pDerived; delete g_pDerived2; return 0; }
程序输出：
Derived destructor Derived::vfunc MemberClass2 destructor Derived::vfunc MemberClass destructor Derived::vfunc Base4 destructor Base4::vfunc Base2 destructor Base2::vfunc Base2_Base destructor Base2_Base::vfunc Base4_Base destructor Base4_Base::vfunc Base5 destructor Base5::vfunc Base5_Base destructor Base5_Base::vfunc Base3 destructor Base3::vfunc Base3_Base destructor Base3_Base::vfunc Base destructor Base::vfunc Base_Base destructor Base_Base::vfunc