Knowledge Base

PRB: FLL Causes Error After Recompilation

Article ID: 198130

Article Last Modified on 12/11/2003

Microsoft Visual C++ 6.0 Enterprise Edition
Microsoft Visual C++ 6.0 Professional Edition
Microsoft Visual C++ 6.0 Standard Edition
Microsoft Visual FoxPro 3.0 Standard Edition
Microsoft Visual FoxPro 3.0b Standard Edition
Microsoft Visual FoxPro 5.0 Standard Edition
Microsoft Visual FoxPro 5.0a
Microsoft Visual FoxPro 6.0 Professional Edition

This article was previously published under Q198130

SYMPTOMS

After building an FLL in Visual C++ 6.0, you may get one of the following error messages when calling a function in the FLL from Visual FoxPro:

API Caused an Exception

The error occurs when loading the debug build of the FLL, but not with the release build.

CAUSE

The project has been compiled in Visual C++ version 6.0 with debug information using the new "Edit and Continue" format. This is why a release build of the FLL works and a debug build that uses "Edit and Continue" for the debug information format fails. The default setting for a debug build in Visual C++ 6.0 is to use a "Program database for Edit and Continue." This causes tokens to be inserted in the compiled program that are not recognized by FoxPro.

NOTE: It appears that the errors occur only when compiling on Windows NT.

RESOLUTION

Use one of the following workarounds:

Compile the project as a release build.
Change the project settings. In the Project Settings dialog box, click the C/C++ tab. Select General in the Category box, and change the selection in the Debug Info: box from "Program database for Edit and Continue" to "Program Database."

STATUS

This behavior is by design.

MORE INFORMATION

Steps to Reproduce Behavior

Locate the HOME()+"Api\Samples" folder.
In Visual C++ 6.0, start a new Win32 Dynamic Link Library project named Reverse.
Add Reverse.C (found in HOME()+"Api\Samples\") to the project.
In the Project Settings, make sure the /MDd compiler switch is used. Add winapims.lib (found in HOME()+"Api\Samples\") to the Object/library modules setting.
On the Build menu of Visual Studio, click "Set Active Configuration," and select Win32 Debug.
Click Rebuild All on the Build menu.
SET LIBRARY TO the newly-compiled Reverse.Dll.
In the Command window, type "? reverse('test')", and note that one of the two error messages listed above appears.

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Mike Stewart, Microsoft Corporation.

Keywords: kbprb KB198130