Re: E_NOINTERFACE error in ATL server extension dll

"Alexander Nickolov" <>
Mon, 1 Oct 2007 13:08:52 -0700
With the limited code snippet you are posting I have no idea.
Most likely a message loop is irrelevant to your code. In fact,
most likely you should be using MTA instead of STA...

Alexander Nickolov
Microsoft MVP [VC], MCSD

"rtischer" <> wrote in message

On Oct 1, 11:50 am, "Alexander Nickolov" <> wrote:

You are leaking an interface pointer each time you unmarshal,
might that be related to your issue?

What you are doing is you are creating a new STA within each
of your methods, then you get an interface pointer and then
you close the STA thus both invalidating the interface pointer
and orphaning it. I'm surprised you don't get a crash in the
destructor of CComPtr<> since it contains garbage at this
point (e.g. after CoUninitialize)...

Alexander Nickolov
Microsoft MVP [VC], MCSD

"rtischer" <> wrote in message

On Sep 30, 4:23 pm, "Alexander Nickolov" <> wrote:

The problem is in your calls to CoInitializeEx and CoUninitialize.
Lose them (move them to the beginning and end of your thread
respectively) and you should be fine.

Alexander Nickolov
Microsoft MVP [VC], MCSD

"rtischer" <> wrote in message

I am getting this error when calling GetInterfaceFromGlobal in an
extension dll in my ATL server. My calling code looks like this:

CComPtr< IMyCallback > myCallback;
HRESULT result = globalInterfaceTable-

GetInterfaceFromGlobal( gitCookie,

 IID_IAtlMyCallback, ( VOID ** )&myCallback );

I know the code is good because I can put it directly in a spawned
worker thread and the GIT call returns S_OK. Also, since my
application code is well tested, I know the problem is not in the
thread switching or the extension dll loading or execution. This
that either ATL GIT marshalling has a problem with PostThreadMessage
or extension dlls.

To test this out, I put the above code directly into the
PostThreadMessage handler and it too worked fine returning an S_OK.
But going one step further and calling a function in the extension
from the message handler, and the code fails returning

Is there some peculiarity with marshalling that I don't know? I am
using the STA threading model. I'm an old hand at MFC and threads,
am relatively new concerning ATL's need for marshalling across
in an ATL Server.- Hide quoted text -

- Show quoted text -

I moved the CoInitializeEx to the beginning and CoUninitialize to the
end of the thread but there was no change. The first call to
GetInterfaceFromGlobal succeeds, but the second call fails. Here is
the code with the initialization surrounding each call. Both calls
occur in the switched-to thread, but the second call occurs in the dll

atlServerApp->PostThreadMessage( SOME_THREAD_HANDLER, wParam,
lParam );
void SomeWinAppThread::SomeThreadHandler( wParam, lParam )
 CComPtr< IMyCallback > myCallback;
 result = globalInterfaceTable->
 GetInterfaceFromGlobal( gitCookie, IID_IAtlMyCallback,
   ( VOID ** )&myCallback ); <-- returns S_OK


void MyExtDll::MyExtDllMethod(...)
 CComPtr< IMyCallback > myCallback;
 result = globalInterfaceTable->
 GetInterfaceFromGlobal( gitCookie, IID_IAtlMyCallback,
   ( VOID ** )&myCallback ); <-- returns S_NOINTERFACE

A colleague of mine suggested that the problem might be due to the
type of dll: extension dlls don't have their own message pump and STA
marshalling depends on that (I'm still reading up on this). This would
mean that I should switch to a regular dll which does have its own
message pump.- Hide quoted text -

- Show quoted text -

Thanks for clearing up my apartment creation problem. I understand now
that an STA apartment should only be created once when the thread is
created and that that is what CoInitializeEx does. Since the problem
still exists, we are back to the idea of message pump (regular dll)
vs. no message pump (extension dll). Could that be the problem?

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