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

ID: Q151034

The information in this article applies to:

The Microsoft Foundation Classes (MFC), included 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 kbMFC kbVC
Version : 4.00 4.10 | 4.00 4.10
Platform : NT WINDOWS
Issue type :