Weird IDL error after migration to VS2010

Question

Here's a very simple IDL interface that we've used successfully under VS2008 (arguments list shortened for brevity):

interface Mailer
{
    string findNode( [in] string requestedNode );
    unsigned short addMessage( [in] string msg, [in] unsigned short kind );
};

We're migrating the solution to VS2010 SP1. Now we have the following build error:

M.idl(3): error MIDL2025: syntax error : expecting a type specification near "string"

This always worked like a charm using VS2008 SP1 Note that I already replaced in by [in]. While scratching my head, I discovered that MIDL 2010 also dislikes in but don't say anything about [in].

Note that unsigned short is accepted (as observed by inverting the 2 methods of the interface).

How come? How can I make MIDL understand string again ?

TIA.

string is an attribute in IDL but can only appear inside [brackets] and must be followed by a type specifier. The way you are using it suggest that you simply forgot to include a definition of your own type named "string". — Hans Passant, Sep 06 '11 at 19:16

score 1 · Answer 1 · answered Sep 06 '11 at 10:39

1

Looks like compiler doesn't know about type 'string', maybe you forgot to include some reference in project, or it's location changed in VS2010, etc. Double check for includes, references and a like.

P.S. Does that makes sense?

answered Sep 06 '11 at 10:39

Petr Abdulin

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Actually, I didn't need additional references. It's the other way around: I needed to remove this file:-) +1 for your help anyway. – Serge Wautier Sep 14 '11 at 14:03

Ghita · Answer 2 · 2011-09-06T16:50:21.437

0

For exposing from C# ,this:

  interface Mailer
    {
        [return, MarshalAs(UnmanagedType.BStr)]
        string findNode( [In, MarshalAs(UnmanagedType.BStr)] string requestedNode );
        unsigned short addMessage( [In, MarshalAs(UnmanagedType.BStr)] string msg, [in] unsigned short kind );
    };

I saw that you possibly mean exposing it from C++:

interface Mailer
{
    HRESULT findNode( [out, retval] BSTR* result, [in] BSTR requestedNode );
    HRESULT addMessage( [out, retval] unsigned short* result, [in] BSTR msg, [in] unsigned short kind );
};

edited Sep 06 '11 at 16:50

answered Sep 06 '11 at 16:44

Ghita

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You also need to use: using System.Runtime.InteropServices; – Ghita Sep 06 '11 at 16:46
Thanks for your answer but .NET is not involved in this project. – Serge Wautier Sep 14 '11 at 14:01

score 0 · Accepted Answer · answered Sep 14 '11 at 14:02

It appears that the IDL file, although present in the project, isn't used at all. VS2008 silently ignored it (as it would do for an unreferenced .h file). For some reason, VS2010 tries to compile it even if it's not referenced anywhere else. And since the contents is totally buggy (string is indeed not a native IDL type but an attribute as best), I now have errors.

Solution: Exclude file from project!

Weird IDL error after migration to VS2010

3 Answers3