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

From:
"Igor Tandetnik" <itandetnik@mvps.org>
Newsgroups:
microsoft.public.vc.atl
Date:
Fri, 30 Jun 2006 08:17:56 -0400
Message-ID:
<evsl48DnGHA.4448@TK2MSFTNGP04.phx.gbl>
"Vi2" <sharachov@hotmail.com> wrote in message
news:1151639732.094095.165420@x69g2000cwx.googlegroups.com

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 {
    [local]
    HRESULT Local(long x);

    [call_as(Local)]
    HRESULT Remote(double x);
};

// MIDL-generated header
    MIDL_INTERFACE("5FFDE818-48AE-4A19-8BF2-30080D81347E")
    ITest : public IUnknown
    {
    public:
        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

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