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Q251402: PRB: Windows Hook Stops Responding in a 16-Bit Application

Article: Q251402
Product(s): Microsoft Windows Software Development Kit
Version(s): WINDOWS:4.0,95
Operating System(s): 
Keyword(s): kbHook kbGrpDSUser kbOSWin95 kbOSWin98 kbDSupport
Last Modified: 15-DEC-2000

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 4.0, on platform(s):
   - Microsoft Windows 98 
   - Microsoft Windows 95 
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SYMPTOMS
========

A global Windows hook, for example a mouse hook, stops responding (crashes) when
triggered by a 16-bit application.

CAUSE
=====

The problem occurs when the hook dynamic-link library (DLL) is built by using
the Visual C++ 6.0 Service Pack 2 (SP2) development environment. The problem
also occurs when the hook project is using the multithreaded DLL C run-time
library (/MD) option.

The Libcmt.lib file that is replaced by SP2 has a bug that can cause this type of
behavior. The versions of Libcmt.lib from SP1 and SP3 do not exhibit this
behavior.

RESOLUTION
==========

To prevent this problem, do not use Libcmt.lib from Visual C++ version 6.0 SP2.
Either install Visual C++ 6.0 SP1 or Visual C++ 6.0 SP3, or use Libcmt.lib from
a Visual C++ 6.0 SP1 or SP3 installation and rebuild the DLL.

If you are using the /MD or multithreaded DLL C run-time library option, you must
switch to the static multithreaded option (/MT).

STATUS
======

This problem is caused by a regression bug in the Visual C++ version 6.0 SP2
development environment.

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

Steps to Reproduce Behavior
---------------------------

1. Build a system-wide keyboard/mouse hook by using Visual C++ 6.0 SP2.

2. Install the system-wide hook.

3. Start any 16-bit application.

4. When mouse (in the case of a mouse hook) or keyboard (in the case of a
  keyboard hook) input occurs on the 16-bit application, the program stops
  responding (crashes).

Alternatively:

1. Build a system-wide keyboard/mouse hook by using the /MD compiler switch.

2. Install the system-wide hook.

3. Start any 16-bit application.

4. When mouse (in the case of a mouse hook) or keyboard (in the case of a
  keyboard hook) input occurs on the 16-bit application, the program stops
  responding (crashes).

Additional query words:

======================================================================
Keywords          : kbHook kbGrpDSUser kbOSWin95 kbOSWin98 kbDSupport 
Technology        : kbAudDeveloper kbSDKSearch kbWinSDKSearch
Version           : WINDOWS:4.0,95
Issue type        : kbprb

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