Assert when calling MFC DLL from VB

Lawrence_Chan@pcmailap.japan.ml.com
Thursday, January 23, 1997

     Environment: NT3.51 VC++ 4.1
     
     I am building a VB application that will display .avi files 
     continously. To do that, I created a MFC Dll with the following 
     functions,
     
     BOOL CAnmApp::InitAnimation(HWND hwnd, LPSTR lpszFile)
     {
        CWnd* pFrame;
        pFrame= pFrame->FromHandle(hwnd);
        ASSERT(pFrame);
        CRect rect;
        pFrame->GetClientRect(&rect);
        m_ctlAnm.Create(WS_CHILD|WS_VISIBLE|WS_BORDER|ACS_CENTER, rect,     
                        pFrame, 89);
     
     
        m_ctlAnm.Open(lpszFile);       
        m_ctlAnm.Play(0, -1, -1);
        return TRUE;
     }
        
     and 
     
     extern "C" BOOL FAR PASCAL EXPORT InitAnimation(HWND hwnd, LPSTR 
     lpszFileName)
     {
        TRY
        {
                
            return ((CAnmApp *) AfxGetApp())->InitAnimation(hwnd,           
                        lpszFileName);
                
        }
        END_TRY 
        return FALSE;
     }
     
     
     No problem when the calling app is a MFC application. However, when I 
     call InitAnimation from VB it gives an assertion fault at file 
     afxwin2.inl line 92. Apparently it fails at the create statement of 
     CAnimateCtrl.
     
     
     the declaration in VB is like that
     
     Declare Function InitAnimation Lib 
     "c:\msdev\projects\anm\debug\anm.dll" (hwnd As Long, ByVal filename As 
     String) As Boolean
     
     
     Any comments.
     Thanks.
     Lawrence

---

Mike Blaszczak -- mikeblas@nwlink.com
Friday, January 24, 1997

[Mini-digest: 2 responses]

At 16:56 1/23/97 JST, Lawrence_Chan@pcmailap.japan.ml.com wrote:
>     Environment: NT3.51 VC++ 4.1

>     BOOL CAnmApp::InitAnimation(HWND hwnd, LPSTR lpszFile)
>     {
>        CWnd* pFrame;
>        pFrame= pFrame->FromHandle(hwnd);
>        ASSERT(pFrame);
>        CRect rect;
>        pFrame->GetClientRect(&rect);


>     No problem when the calling app is a MFC application. However, when I 
>     call InitAnimation from VB it gives an assertion fault at file 
>     afxwin2.inl line 92. Apparently it fails at the create statement of 
>     CAnimateCtrl.

Is it, really?  What's the stack trace look like? 

The assertion you site is for GetClientRect() to determine if the CWnd
object really has a window or not.  If you're tripping this assertion,
the CWnd object is invalid.

It looks like you call GetClientRect() yourself against pFrame.  Is that
the call that causes the assertion, or is it somewhere during the
creation of the animation control?  It would surprise me if CAnimate::Create()
was calling CWnd::GetClientRect().

I think you've mis-diagnosed this problem.  A stack trace at the assertion
would confirm or eliminate your diagnosis.


.B ekiM
http://www.nwlink.com/~mikeblas/
Why does the "new" Corvette look like a 1993 RX-7?
These words are my own. I do not speak on behalf of Microsoft.

-----From: David Razzetti 

Laurence -=20

You don't provide enough information about your DLL.

How have you linked it to the MFC libraries ?
If you created the app using ApWizard, you should have chosen one of
:-
	Regular DLL with MFC statically linked
	Regular DLL using shared MFC dll

You have not allowed for module state information management inside
your exported fuction.
You "probably" need to add the line :-

	AFX_MANAGE_STATE( AfxGetStaticModuleState() );

so that its the first line executed in your function.  See the VC++
help article named "Managing the state data of MFC modules".  Its very
informative.

Dave Razzetti
raz@jump-jet.demon.co.uk

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