关于什么时候使用CoTaskMemAlloc/CoTaskMemFree来申请/释放内存

从网上看来的说法：
The thing is that COM (actually the RPC runtime library, but it's easier to blame COM) has an additional requirement for [out] pointers.  This requirement is that if the type of an [out] parameter isn't a scalar quantity (in other words if it's a structure or anything more complicated than a int or float), then the memory pointed to by the [out] parameter needs to be allocated either by MIDL_user_allocate (for RPC) or CoTaskMemAlloc (for COM).

也就是说，如果需要调用COM接口，并且接口中有[out]的参数，且类型不是整形或浮点数之类的基本数据类型，就需要调用CoTaskMemAlloc来申请这块内存，并使用完毕后调用CoTaskMemFree来释放。