Interface inheritance between different COM modules?

From:

Axel Bock <axel.bock.news@googlemail.com>

Newsgroups:

microsoft.public.vc.atl

Date:

Thu, 21 Jun 2007 23:44:12 -0700

Message-ID:

<1182494652.692344.167660@w5g2000hsg.googlegroups.com>

Hi,

I have a - hopefully - simple problem. I need to write an Interface
INT_B in a COM component COM_B, which actually inherits from an
interface INT_A from COM component COM_A.

I try to do this by importlib'ing the COM_A.dll file in the COM_B.idl,
and write the following line:

interface IINT_B : IINT_A { };

Where IINT_A is defined in the COM_A.dll file. Alas I get a MIDL
compiler error: COM_B.idl(31) : warning MIDL2271 : [object] interfaces
must derive from another [object] interface such as IUnknown :
[ Interface 'IINT_A' (IINT_A' ) ].

If I use another interface defined in the same file it works
beautifully.
If I include the COM_A.idl file I get some weird errors saying "could
not find COM_A.h file".
If I do something else ... well, I don't know of something else :-) .

Can anybody help? I included parts of the IDL files below for
reference.

Many thanks in advance & greetings,
Axel.

p.s.: If I am off-topic here, please, where should I post this?

----------------- IDL files -----------------

I deleted the properties etc. from the files and all the other classes
for readability ...

=====================
COM_A.dl IDL file:
=====================

[
    object,
    uuid(F5BDF49A-0F59-4EFA-B328-74C2DEB83E4F),
    dual,
    helpstring("IServiceQualifier-Schnittstelle"),
    pointer_default(unique)
]
interface IServiceQualifier : IDispatch{ };

library ComLscLib
{
    importlib("stdole2.tlb");
    [
        uuid(8EF7F82E-5732-4472-902B-8B1CCEB408A3),
        helpstring("ServiceQualifier Class")
    ]
    coclass ServiceQualifier
    {
        [default] interface IServiceQualifier;
    };
};

=====================
COM_B.dl IDL file:
=====================

[
    object,
    uuid(8DF23D05-A88B-4F59-B7DD-D991469F5B9A),
    dual,
    nonextensible,
    helpstring("IConfigurationServiceQualifier-Schnittstelle"),
    pointer_default(unique)
]
interface IConfigurationServiceQualifier : IServiceQualifier {
};

[
    uuid(C4E69D50-01F7-42C1-9CCB-06DCFA02E524),
    version(1.0),
    helpstring("ServiceConfiguration 1.0-Typbibliothek")
]
library ServiceConfigurationLib
{
    importlib("stdole2.tlb");
    importlib("..\ComLsc\Debug\ComLsc.dll");
    [
        uuid(BC0136D0-2913-4B31-ACEA-7515F1E2ADAB),
        helpstring("ConfigurationServiceQualifier Class")
    ]
    coclass ConfigurationServiceQualifier
    {
        [default] interface IConfigurationServiceQualifier;
    };
};