VB function called from c++

From:

"Jake" <jakethedog317@yahoo.com>

Newsgroups:

microsoft.public.vc.language

Date:

20 Nov 2006 13:53:19 -0800

Message-ID:

<1164059599.284957.119390@j44g2000cwa.googlegroups.com>

I have a C++ function that calls a VB dll but I am not that familiar
with VB in order to resolve the crash that I am having.

This is my code

int u_dll_imstest_call(wchar_t *TheConnectString, wchar_t *TheTable,
wchar_t *TheFields, wchar_t *ThePopupTitle, wchar_t *TheOrderBy,
wchar_t *TheWhereClause, wchar_t *ThePosition)
{
    // Declare an HRESULT and a pointer to the clsVBTestClass interface
    HRESULT hr;

    BSTR bTheConnectString = L"Provider = Microsoft.Jet.OLEDB.4.0;Data

Source=C:\\Imstestfor8.2\\database\\CAT16.mdb";
    BSTR bTheTable = L"USR";
    BSTR bTheFields = L"USERNAME,Name,USER_ID,ID,U_LOGIN,Log-in";
    BSTR bThePopupTitle = L"User Table";
    BSTR bTheOrderBy = L"USERNAME";
    BSTR bTheWhereClause = L"!=0000000001";
    BSTR bThePosition = L"b";

    _bstr_t value;

    _clsCat16 *IclsCat16 = NULL;
    // Now we will intilize COM
    hr = CoInitialize(0);

    // Use the SUCCEEDED macro and see if we can get a pointer
    // to the interface
    if(SUCCEEDED(hr))
    {
        hr = CoCreateInstance(__uuidof (clsCat16),
                      NULL,
                      CLSCTX_INPROC_SERVER,
                      _uuidof (_clsCat16),
                      (void**) &IclsCat16);

        // If we succeeded then call the CountStringLength method,
        // if it failed then display an appropriate message to the user.
        if(SUCCEEDED(hr))
        {

            value = IclsCat16->Popup(&bTheConnectString, &bTheTable,

              &bTheFields, &bThePopupTitle,

              &bTheOrderBy, &bTheWhereClause,

              &bThePosition);
            return 0;
        }
        else
        {
        }
    }
    // Uninitialize COM
    CoUninitialize();
    return 0;
}

I am using #import "WFCat16.dll" no_namespace in order to import the
tlh file

This is what the function looks like in the tlh

struct __declspec(uuid("21eb71ba-4e5f-4948-9315-b38c29fd296c"))
_clsCat16 : IDispatch
{
    //
    // Wrapper methods for error-handling
    //

    _bstr_t Popup (
        BSTR * TheConnectString,
        BSTR * TheTable,
        BSTR * TheFields,
        BSTR * ThePopupTitle,
        BSTR * TheOrderBy,
        BSTR * TheWhereClause,
        BSTR * ThePosition );

    //
    // Raw methods provided by interface
    //

      virtual HRESULT __stdcall raw_Popup (
        /*[in,out]*/ BSTR * TheConnectString,
        /*[in,out]*/ BSTR * TheTable,
        /*[in,out]*/ BSTR * TheFields,
        /*[in,out]*/ BSTR * ThePopupTitle,
        /*[in,out]*/ BSTR * TheOrderBy,
        /*[in,out]*/ BSTR * TheWhereClause,
        /*[in,out]*/ BSTR * ThePosition,
        /*[out,retval]*/ BSTR * _arg8 ) = 0;
};

I guess my question is am I right in defining my input as BSTR and then
sending the address of the data to the VB function?

I am using _bstr_t to define my return value because that is how it
should be returned from the VB call - Do I need to allocate the _bstr_t
field before I use it? This is what gets called or what I see when I
debug

inline _bstr_t _clsCat16::Popup ( BSTR * TheConnectString, BSTR *
TheTable, BSTR * TheFields, BSTR * ThePopupTitle, BSTR * TheOrderBy,
BSTR * TheWhereClause, BSTR * ThePosition ) {
    BSTR _result = 0;
    HRESULT _hr = raw_Popup(TheConnectString, TheTable, TheFields,
ThePopupTitle, TheOrderBy, TheWhereClause, ThePosition, &_result);
    if (FAILED(_hr)) _com_issue_errorex(_hr, this, __uuidof(this));
    return _bstr_t(_result, false);

It seems to bail on the if (FAILED(_hr)) _com_issue_errorex(_hr, this,
__uuidof(this));

In the debugger I can see that the values are being passed so I am
confused.

Eventually I want to take wchar_t * values and send them to this
function but for right now I just trying to get it to work - Anybody
have any ideas?

Thanks
Jake