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Q130667: PRB: F12 Causes Hard-Coded Breakpoint Exception When Debugging

Article: Q130667
Product(s): Microsoft C Compiler
Version(s): WINDOWS NT:1.0,2.0,2.1,4.0,5.0
Operating System(s): 
Keyword(s): kbDebug kbide kbVC100 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600
Last Modified: 27-JUL-2001

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The information in this article applies to:

- The Integrated Debugger, included with:
   - Microsoft Visual C++, 32-bit Editions, versions 1.0, 2.0, 2.1, 4.0 
   - Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0 
   - Microsoft Visual C++, 32-bit Professional Edition, version 5.0 
   - 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
========

When debugging an application under Windows NT, pressing the F12 key when the
debuggee (the application) has focus causes the integrated debugger to pause the
debuggee and display a dialog with one of the following messages:

  Break caused by hard coded breakpoint instruction.

-or-

  User breakpoint called from code at <address>

This occurs only under Windows NT, not under any other Win32 platform.

CAUSE
=====

When the F12 key is pressed and the application in focus is being debugged,
Windows NT calls a function similar to DebugBreak(), which executes a hard coded
breakpoint instruction. The integrated debugger then traps the exception
generated by this instruction.

This behavior is intentional and occurs with other debuggers such as WinDbg from
the Windows 32-bit SDK.

RESOLUTION
==========

While there is no way to disable this functionality, it doesn't affect the
application that's being debugged other than to pause debugging and change
focus. You can continue debugging by pressing the F5 key.

This can be annoying if you have an application that heavily uses the F12 key, so
you may want to temporarily assign another key to handle the F12 key
functionality in your program when debugging.

STATUS
======

This behavior is by design.

Additional query words: IDE

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Keywords          : kbDebug kbide kbVC100 kbVC200 kbVC210 kbVC400 kbVC500 kbVC600 
Technology        : kbVCsearch kbAudDeveloper kbIntegratedDebugger
Version           : WINDOWS NT:1.0,2.0,2.1,4.0,5.0
Issue type        : kbprb

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