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Q147894: BUG: Spy++ Causes Exception in Owner-Drawn Combo Box

Article: Q147894
Product(s): Microsoft C Compiler
Version(s): 6.0
Operating System(s): 
Keyword(s): 
Last Modified: 31-JUL-2001

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
- Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
- Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
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SYMPTOMS
========

Using Spy++ with message logging on an owner-drawn combo box results in one of
the following errors:

  First-chance exception in OWNCOMBO.exe (USER32.DLL): 0xC0000005: Access
  Violation.

  -or-

  First-chance exception in OWNCOMBO.exe (KERNEL32.DLL): 0xC0000005: Access
  Violation.

This exception is printed out in the Visual C++ debug output window. This happens
both on Windows 95 and Windows NT version 3.51.

RESOLUTION
==========

This exception is caused by the Spy++ installed Windows hook function. It
doesn't cause the program to quit, so no action should be necessary.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. We are researching this problem and will post new
information here in the Microsoft Knowledge Base as it becomes available.

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

In the sample used to produce this error, the owner-drawn combo box did not have
the style CBS_HASSTRINGS. A 32-bit value was being passed to the combo box by
way of CB_ADDSTRING. This appears to cause the exception when the Spy++ message
logging is turned on.

This error did not occur in previous versions of Spy++.

Steps to Reproduce Error
------------------------

1. Load the project of the OWNCOMBO sample as provided with Visual C++ 4.0.

2. On the Build menu, click Rebuild All to get a debug executable.

3. Start Owncombo.exe by pressing F5.

4. On the View menu, click Output in Visual C++ 4.0.

5. Start Spy++ and move its window as well as OWNCOMBO's window so that MSDEV's
  output window is visible.

6. In OWNCOMBO, on the Examples menu, click Owner Draw Combo Box.

7. In Spy++, on the Spy menu, click Find Window.

8. Use the Finder Tool, and drag it over the combo box in OWNCOMBO.

9. In Spy++, under Show, click Messages, and then click OK.

10. In OWNCOMBO, add a color to the combo box (either Red or Blue).

Additional query words: kbVC400bug 4.00 4.10 4.20

======================================================================
Keywords          :  
Technology        : kbVCsearch kbAudDeveloper kbVC600 kbVC32bitSearch
Version           : :6.0

=============================================================================

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