Calling a COM dll from c++, "Class Not Registered" - c++

Question

I have created a COM dll in Microsoft Visual Basic 2008. I am trying to call this dll from a C++ project. In the C++ I used "#import U:\path...\MyComDll.tlb" I then used the following code to the DisplayMessage() method.
FB::variant CmdAccessAPI::filePSV(std::string file)
{
CoInitialize(NULL);
try
{
_MyComClassPtr spIMyComClass;
HRESULT hr = spIMyComClass.CreateInstance(__uuidof(_MyComClass));
if (FAILED(hr)) throw _com_error(hr);
spIMyComClass->DisplayMessage();
}
catch (std::exception& e)
{
CString strMsg(e.what());
MessageBox(NULL, strMsg, L"Error", MB_OK);
}
catch (_com_error& e)
{
CString strMsg;
strMsg = (TCHAR*) e.Description();
strMsg += _T("\n");
strMsg += (TCHAR*) e.ErrorMessage();
MessageBox(NULL, strMsg, L"COM Error", MB_OK);
}
CoUninitialize();
return "test";
}
When I call this function I get a Class Not Registered error. I have tried to register the dll using regsvr32 and I get the message "MyComDll.dll was loaded, but the DLLREgeisterServer entry point was not found. This file can not be registered."
How do I register the class and get this to work?

Answer 1

Try registering it using admin privileges,
Right click on the Command prompt and choose run as administrator, and give the systems 32 path.
Then use regsvr32 xyz.dll

Answer 2

If you can't register it, there are two possibilities
You are missing a dependent library. Download dependency walker and see what's missing. Some of the ones that are marked missing are red herrings (ieshims.dll for example), but one of them may be yours
Something went way off the rails in your COM setup. You can debug your dll as its being registered and dig into the ATL code where its failing.

Answer 3

You need to use regsvr32 to register the DLL, as you suspect.
However, the error its giving suggests that either the DLL doesn't have the stub included (and so cannot register itself) or you're trying to register the library, not the stub.
Make sure your VS project and the code is set up to include the proxy/stub functions in your DLL, or make sure you register the proxy DLL.

Answer 4

**include the below code** and export these functions with .def file
wchar_t *convertCharArrayToLPCWSTR(const char* charArray)
{
wchar_t* wString=new wchar_t[4096];
MultiByteToWideChar(CP_ACP, 0, charArray, -1, wString, 4096);
return wString;
}
BOOL Register( HKEY mainKey,const char *subKey,LPCTSTR val_name, DWORD dwType,char * chardata,DWORD dwDataSize)
{
HKEY hk;
if (ERROR_SUCCESS != RegCreateKey(mainKey,convertCharArrayToLPCWSTR(subKey),&hk) )
return FALSE;
LPCTSTR data=convertCharArrayToLPCWSTR(chardata);
if (ERROR_SUCCESS != RegSetValueEx(hk,val_name,0,dwType,(CONST BYTE *)data,2*dwDataSize))
return FALSE;
if (ERROR_SUCCESS != RegCloseKey(hk))
return FALSE;
return TRUE;
}
HRESULT __stdcall DllRegisterServer(void)
{
WCHAR *lpwszClsid;
char szBuff[MAX_PATH]="new multiplication Algorithm";
char szClsid[MAX_PATH]="", szInproc[MAX_PATH]="",szProgId[MAX_PATH];
char szDescriptionVal[256]="";
StringFromCLSID(CLSID_MultiplicationObject,&lpwszClsid);
sprintf(szClsid,"%S",lpwszClsid);
sprintf(szInproc,"%s\\%s\\%s","clsid",szClsid,"InprocServer32");
sprintf(szProgId,"%s\\%s\\%s","clsid",szClsid,"ProgId");
sprintf(szDescriptionVal,"%s\\%s","clsid",szClsid);
Register (HKEY_CLASSES_ROOT,szDescriptionVal,NULL,REG_SZ,szBuff,strlen(szBuff));
//InprocServer32
GetModuleFileNameA(g_hModule,szBuff,sizeof(szBuff));
Register (HKEY_CLASSES_ROOT,szInproc,NULL,REG_SZ,szBuff,strlen((szBuff)));
//ProgId
strcpy(szBuff,multiplicationObjProgId);
Register (HKEY_CLASSES_ROOT,szProgId,NULL,REG_SZ,szBuff,strlen(szBuff));
return 1;
}
HRESULT __stdcall DllUnregisterServer(void)
{
WCHAR *lpwszClsid;
char szBuff[MAX_PATH]="new multiplication Algorithm";
char szClsid[MAX_PATH]="", szInproc[MAX_PATH]="",szProgId[MAX_PATH];
char szDescriptionVal[256]="";
StringFromCLSID(CLSID_MultiplicationObject,&lpwszClsid);
sprintf(szClsid,"%S",lpwszClsid);
sprintf(szInproc,"%s\\%s\\%s","clsid",szClsid,"InprocServer32");
sprintf(szProgId,"%s\\%s\\%s","clsid",szClsid,"ProgId");
sprintf(szDescriptionVal,"%s\\%s","clsid",szClsid);
RegDeleteKey(HKEY_CLASSES_ROOT,convertCharArrayToLPCWSTR(szInproc));
RegDeleteKey(HKEY_CLASSES_ROOT,convertCharArrayToLPCWSTR(szProgId));
RegDeleteKey(HKEY_CLASSES_ROOT,convertCharArrayToLPCWSTR(szDescriptionVal));
return 1;
}

Answer 5

This kind of dependency problem can happen when there is a mismatch in vendor architecture.
For example, you may have registered the 32bit DLL but your program is 64bit or vice-versa.