Problems with a static library

Jon McCulloch -- sensei@anglianet.co.uk
Friday, November 01, 1996

Environment: NT 3.51, Visual C++ 4.0

I have an applicatiion for which I'm trying to create and use an static library.

At the moment all I'm trying to do is call a GetPassword() function from the
library.

The code looks like this:

Application:

CString strPassword;
CString strPrincipal; // username

strPassword = GetPassword(strPrincipal);


where the function prototype is: CString GetPassword(const CString&).

Library:

GetPassword() looks like this:

CString GetPassword(const CString& strUsername)
{ 
  CString strPassword;
  CGetPasswordDlg dlg;

  dlg.DoModal();

  return strPassword;
} // end of GetPassword()

All I'm trying to do at the momebnt is display the bloody dialog box, never
mind exchange andy data.

CGetPasswordDlg is just a dialog-box class:

// GetPasswordDlg.cpp : implementation file
//

#include "stdafx.h"
#include "sdiwin32.h"
#include "resource.h"
#include "GetPasswordDlg.h"

#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif

/////////////////////////////////////////////////////////////////////////////
// CGetPasswordDlg dialog


CGetPasswordDlg::CGetPasswordDlg(CWnd* pParent /*=NULL*/)
	: CDialog(CGetPasswordDlg::IDD, pParent)
{
	//{{AFX_DATA_INIT(CGetPasswordDlg)
	m_Password = _T("");
	//}}AFX_DATA_INIT
}


void CGetPasswordDlg::DoDataExchange(CDataExchange* pDX)
{
	CDialog::DoDataExchange(pDX);
	//{{AFX_DATA_MAP(CGetPasswordDlg)
	DDX_Text(pDX, IDC_GET_PASSWORD, m_Password);
	DDV_MaxChars(pDX, m_Password, 10);
	//}}AFX_DATA_MAP
}


BEGIN_MESSAGE_MAP(CGetPasswordDlg, CDialog)
	//{{AFX_MSG_MAP(CGetPasswordDlg)
		// NOTE: the ClassWizard will add message map macros here
	//}}AFX_MSG_MAP
END_MESSAGE_MAP()

And the header file looks like this:

//
// GetPasswordDlg.h : header file
//

/////////////////////////////////////////////////////////////////////////////
// CGetPasswordDlg dialog

class CGetPasswordDlg : public CDialog
{
// Construction
public:
	CGetPasswordDlg(CWnd* pParent = NULL);   // standard constructor

// Dialog Data
	//{{AFX_DATA(CGetPasswordDlg)
	enum { IDD = IDD_GETPASSWORD };
	CString	m_Password;
	//}}AFX_DATA


// Overrides
	// ClassWizard generated virtual function overrides
	//{{AFX_VIRTUAL(CGetPasswordDlg)
	protected:
	virtual void DoDataExchange(CDataExchange* pDX);    // DDX/DDV support
	//}}AFX_VIRTUAL

// Implementation
protected:

	// Generated message map functions
	//{{AFX_MSG(CGetPasswordDlg)
		// NOTE: the ClassWizard will add member functions here
	//}}AFX_MSG
	DECLARE_MESSAGE_MAP()
};

I can compile and link the App. with the calls to GetPassword() with nary a
blip, but when I run it, it bombs out.

I've traced the problem into  CWnd::CreateDlgIndirect(LPCDLGTEMPLATE
lpDialogTemplate, CWnd* pParentWnd) in dlgcore.cpp, specifically, the call 

HWND hWnd = ::CreateDialogIndirect(AfxGetInstanceHandle(), lpDialogTemplate,
		pParentWnd->GetSafeHwnd(), AfxDlgProc);


For some reason that I cannot fathom, this is giving me a run-time error of
"unhandled exception in login.exe (MFC40D.DLL): 0x0000005: Access Violation".

Can anyone suggest what is wrong? The truly annoying thing is that it worked
fine earlier today...

Thanks,

Jon

---

Dong Chen -- d_chen@ix.netcom.com
Sunday, November 03, 1996

[Mini-digest: 2 responses]

At 03:07 PM 11/1/96 +0000, you wrote:
>Environment: NT 3.51, Visual C++ 4.0
>
>I have an applicatiion for which I'm trying to create and use an static
library.
>
>At the moment all I'm trying to do is call a GetPassword() function from the
>library.
>
>The code looks like this:
>
>Application:
>
>CString strPassword;
>CString strPrincipal; // username
>
>strPassword = GetPassword(strPrincipal);
>
>
>where the function prototype is: CString GetPassword(const CString&).
>
>Library:
>
>GetPassword() looks like this:
>
>CString GetPassword(const CString& strUsername)
>{ 
>  CString strPassword;
>  CGetPasswordDlg dlg;
>
>  dlg.DoModal();
>
>  return strPassword;
>} // end of GetPassword()
>
(snip)

My guess is that you probably didn't add the AFX_MANAGE_STATE macro. But
what confused me is that you said it worked earlier. Maybe others can spot
the exact problem.

-----From: "Doug Brubacher" 

     Jon,
     
     Since I do not recognize the error message you talk about, it is 
     pretty hard to tell what is wrong from the information you have 
     provided, none the less I still have a few suggestions:
     
     1. Problem one is, where is the static library getting its resources 
     from?  Any application that uses your static library is going to 
     require all the resources (dialogs resources, string tables, etc.) 
     that the classes in your library require.  Ensure this is true for the 
     current app, otherwise stick all the static library resources in their 
     own DLL. and anywhere in the library that requires a resource do a 
     AfxSetResourceHandle( hStaticLibraryResourceHandle ) before the 
     resource is referenced.  Don't forget to restore the apps resource 
     handle when your done.
     
     2.  You say it worked earlier today?  A Rebuild All never hurts, or 
     more likely have you changed something?  With dialogs if you rename 
     one of the controls that your class is performing Dynamic Data 
     Exchange with you always need to delete the member variable and then 
     re-add it with class wizard or edit the appropriate DDX macro in 
     DoDataExchange.
     
     Regards,
     
     Doug Brubacher
     DouglasB@msn.com

---

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