c++ - 当大小相同时使用派生对象数组作为基础对象数组 (CComVariant/VARIANT)

Question

我使用的代码将派生对象数组视为基础对象数组。两个对象的大小相同。我想知道:

• 这在实践中是否安全，请记住代码只会在 Microsoft 编译器上编译？

这是我的例子:

BOOST_STATIC_ASSERT(sizeof(VARIANT)==sizeof(CComVariant));

//auto_array deletes[] the pointer if detach() isn't called at the end of scope
auto_array<CComVariant> buffer(new CComVariant[bufferSize]);

//...Code that sets the value of each element...

//This takes a range specified as two VARIANT* - the AtlFlagTakeOwnership option
//causes delete[] to be called on the array when the object pEnum referes to 
//is released.
pEnum->Init(buffer.ptr,buffer.ptr+bufferSize,0,AtlFlagTakeOwnership);
buffer.detach();

Answer 1

是的，CComVariant 旨在直接替代 VARIANT。它派生自变体结构，不添加任何虚拟成员或字段(也没有虚拟析构函数)以确保内存布局相同。许多类似 ATL/MFC 中的小帮助类，如 CRect、CPoint 等。