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Q151034: PRB: MFC Control Panel Applet Shows ODBC Icon in Control Panel

Article: Q151034
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1
Operating System(s): 
Keyword(s): kbnokeyword kbDatabase kbMFC kbODBC kbVC400
Last Modified: 30-JUL-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1 
-------------------------------------------------------------------------------

SYMPTOMS
========

The MFC Control Panel applet displays the ODBC icon on the Control Panel with
the functionality of the ODBC data source setup Control Panel applet. The
NTCPLAPP MSDN sample exhibits this behavior.

CAUSE
=====

The applet entry-point function, CPlApplet(), exported by the MFC control
applet, is resolved to the function exported from ODBCCP32.LIB rather than the
function exported from the project.

RESOLUTION
==========

If you are not using any of the functions exported by ODBCCP32.LIB, then select
the Input category in the Project Settings for the linker, and specify
"odbccp32.lib" in the "ignore libraries" field. This is equivalent to adding
/nodefaultlib:"odbccp32.lib" in the linker command line.

However, if you have to link in the ODBCCP32.LIB file, then close the workspace,
open the .mak file for the project as text, and add "odbccp32.lib" to the linker
dependency line as shown in the example below. In the case of the NTCPLAPP
sample, you should see lines similar to the following:

     "$(OUTDIR)\MyCplApp.cpl" : "$(OUTDIR)" $(DEF_FILE)$(LINK32_OBJS)
         $(LINK32) @<<
       $(LINK32_FLAGS) $(LINK32_OBJS)

These lines are the linker dependency and command line. Each target has these
lines. Modify the last line as follows:

     $(LINK32_FLAGS) $(LINK32_OBJS)odbccp32.lib

This ensures that functions exported by the ODBCCP32.LIB file are searched last
while linking. The CPlApplet is resolved to the one in your code because the
.OBJ files are searched prior to the import libraries. If there are multiple
targets, the modification needs to be made for all the targets.

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Every Control Panel application must export the standard entry-point function
CPlApplet that is called by Control Panel in various situations. When you
include AFXDB.H in your project, MFC pulls in the ODBCCP32.LIB file through a
#pragma comment(). This is the import library for the ODBC installation DLL that
also exports CPlApplet. The linker resolves the CPlApplet function from the
ODBCCP32.LIB rather than from your object files. Since CPlApplet resolves to the
one in ODBCCP32.LIB, your Control Panel applet acts as another ODBC Control
Panel applet.

This behavior occurs in an Control Panel applet based on an appwizard- generated
regular DLL project that includes AFXDB.H in STDAFX.H by default.

REFERENCES
==========

Visual C++ Books Online and the Windows SDK documentation.

Additional query words: 4.00 4.10 ODBCCP32 NTSERVCTRL

======================================================================
Keywords          : kbnokeyword kbDatabase kbMFC kbODBC kbVC400 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:4.0,4.1
Issue type        : kbprb

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