vbox之c++对象之父类对象到comPtr子类对象的转化

举个栗子

ComPtr<IMousePointerShapeChangedEvent> pMPSCEv = aEvent;

上面这个在com下是可以编译的，但是实际在vs下无法通过的，通过对原版程序逆向发现，上面这个函数的实现是以下代码

xor     ebx, ebx
mov     [rbp+57h+bstrString], rbx
test    rdi, rdi
jz      short loc_13F3D44B7
mov     rax, [rdi]      //rdi =IEvent *aEvent，eax为虚指针=this
lea     r8, [rbp+57h+bstrString]
lea     rdx, _GUID_a6dcf6e8_416b_4181_8c4a_45ec95177aef
mov     rcx, rdi
call    qword ptr [rax]  //this的第一个函数，通过查表发现是QueryInterface函数

所以上面的操作转换为vs下为：

IMousePointerShapeChangedEvent *pMPSCEv;
IID riid = {0xa6dcf6e8,0x416b,0x4181,{0x8c,0x4a,0x45,0xec,0x95,0x17,0x7a,0xef}};
//通过调试发现实际上，通过QueryInterface函数获取相应的指针
aEvent->QueryInterface(riid,(void **)&pMPSCEv);

IMousePointerShapeChangedEvent的定义

EXTERN_C const IID IID_IMousePointerShapeChangedEvent;

#if defined(__cplusplus) && !defined(CINTERFACE)
    
    MIDL_INTERFACE("a6dcf6e8-416b-4181-8c4a-45ec95177aef")
    IMousePointerShapeChangedEvent : public IEvent
    {
    public:
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Visible( 
            /* [retval][out] */ BOOL *aVisible) = 0;
        
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Alpha( 
            /* [retval][out] */ BOOL *aAlpha) = 0;
        
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Xhot( 
            /* [retval][out] */ ULONG *aXhot) = 0;
        
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Yhot( 
            /* [retval][out] */ ULONG *aYhot) = 0;
        
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Width( 
            /* [retval][out] */ ULONG *aWidth) = 0;
        
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Height( 
            /* [retval][out] */ ULONG *aHeight) = 0;
        
        virtual /* [propget] */ HRESULT STDMETHODCALLTYPE get_Shape( 
            /* [retval][out] */ SAFEARRAY * *aShape) = 0;
        
    };
    
#else   /* C style interface */

    typedef struct IMousePointerShapeChangedEventVtbl
    {
        BEGIN_INTERFACE
        
        HRESULT ( STDMETHODCALLTYPE *QueryInterface )( 
            IMousePointerShapeChangedEvent * This,
            /* [in] */ REFIID riid,
            /* [annotation][iid_is][out] */ 
            __RPC__deref_out  void **ppvObject);
        
        ULONG ( STDMETHODCALLTYPE *AddRef )( 
            IMousePointerShapeChangedEvent * This);
        
        ULONG ( STDMETHODCALLTYPE *Release )( 
            IMousePointerShapeChangedEvent * This);
        
        HRESULT ( STDMETHODCALLTYPE *GetTypeInfoCount )( 
            IMousePointerShapeChangedEvent * This,
            /* [out] */ UINT *pctinfo);
        
        HRESULT ( STDMETHODCALLTYPE *GetTypeInfo )( 
            IMousePointerShapeChangedEvent * This,
            /* [in] */ UINT iTInfo,
            /* [in] */ LCID lcid,
            /* [out] */ ITypeInfo **ppTInfo);
        
        HRESULT ( STDMETHODCALLTYPE *GetIDsOfNames )( 
            IMousePointerShapeChangedEvent * This,
            /* [in] */ REFIID riid,
            /* [size_is][in] */ LPOLESTR *rgszNames,
            /* [range][in] */ UINT cNames,
            /* [in] */ LCID lcid,
            /* [size_is][out] */ DISPID *rgDispId);
        
        /* [local] */ HRESULT ( STDMETHODCALLTYPE *Invoke )( 
            IMousePointerShapeChangedEvent * This,
            /* [in] */ DISPID dispIdMember,
            /* [in] */ REFIID riid,
            /* [in] */ LCID lcid,
            /* [in] */ WORD wFlags,
            /* [out][in] */ DISPPARAMS *pDispParams,
            /* [out] */ VARIANT *pVarResult,
            /* [out] */ EXCEPINFO *pExcepInfo,
            /* [out] */ UINT *puArgErr);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Type )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ VBoxEventType *aType);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Source )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ IEventSource **aSource);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Waitable )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ BOOL *aWaitable);
        
        HRESULT ( STDMETHODCALLTYPE *SetProcessed )( 
            IMousePointerShapeChangedEvent * This);
        
        HRESULT ( STDMETHODCALLTYPE *WaitProcessed )( 
            IMousePointerShapeChangedEvent * This,
            /* [in] */ LONG aTimeout,
            /* [retval][out] */ BOOL *aResult);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Visible )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ BOOL *aVisible);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Alpha )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ BOOL *aAlpha);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Xhot )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ ULONG *aXhot);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Yhot )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ ULONG *aYhot);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Width )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ ULONG *aWidth);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Height )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ ULONG *aHeight);
        
        /* [propget] */ HRESULT ( STDMETHODCALLTYPE *get_Shape )( 
            IMousePointerShapeChangedEvent * This,
            /* [retval][out] */ SAFEARRAY * *aShape);
        
        END_INTERFACE
    } IMousePointerShapeChangedEventVtbl;

    interface IMousePointerShapeChangedEvent
    {
        CONST_VTBL struct IMousePointerShapeChangedEventVtbl *lpVtbl;
    };