Re: distributing a COM library/server for use by other folks for C++

"Igor Tandetnik" <>
Fri, 30 Jun 2006 08:17:56 -0400
"Vi2" <> wrote in message

Igor Tandetnik ?????(?):

Non-automation compatible interfaces should not be put into a type
library in the first place. TLB format cannot represent all the
subtle details, so in worst case #import will (appear to) work but
_generate headers that don't match the original interfaces_.

It seems that this is very strong statement. TLB-driven marshaling
code cannot exactly marshal the non-automation compatible interfaces,
but I cannot say that #imported interface doesn't match (or
correspond to) the original interface. In terms of C|C++, of course.
You have the refuting examples, not?

If you have a pair of methods designated as [local] and [call_as], with
different parameters, then the TLB (and the #import-generated header, of
course) contains only the [call_as] part, but your vtable contains only
the [local] part. E.g.

// IDL
interface ITest : IUnknown {
    HRESULT Local(long x);

    HRESULT Remote(double x);

// MIDL-generated header
    ITest : public IUnknown
        virtual /* [local] */ HRESULT STDMETHODCALLTYPE Local(
            long x) = 0;


// #import-generated .TLH file
struct __declspec(uuid("5ffde818-48ae-4a19-8bf2-30080d81347e"))
ITest : IUnknown
    // Raw methods provided by interface

      virtual HRESULT __stdcall Remote (
        double x ) = 0;

With best wishes,
    Igor Tandetnik

With sufficient thrust, pigs fly just fine. However, this is not
necessarily a good idea. It is hard to be sure where they are going to
land, and it could be dangerous sitting under them as they fly
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