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Specifying the Debugger for Unhandled User Mode Exceptions

This article was previously published under Q121434
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Windows NT allows you to specify a post mortem debugger for unhandled Usermode exceptions. A general protection (GP) fault message is one of the manyexamples of a User mode exception. This allows you to see what went wrongin the code by examining where the program caused the fault, as well as thecondition of registers, memory, and the stack.

By default, Windows NT used a 32-bit version of Dr. Watson as a post mortemdebugger. The Dr. Watson log obtained from application users can be usefulto the developers of the application in determining the cause of failure.

When the Win32 SDK is installed, the default post mortem debugger ischanged to the kernel debugger. When Microsoft Visual C++ version 2.00 isinstalled, the default postmortem debugger is changed to the Visual C++interface.

In order to change the default debugger for unhandled user mode exceptions,do the following:

WARNING: Using Registry Editor incorrectly can cause serious, system-wide problems that may require you to reinstall Windows NT to correct them. Microsoft cannot guarantee that any problems resulting from the use of Registry Editor can be solved. Use this tool at your own risk.

  1. Start Registry Editor and locate the following Registry subkey in the HKEY_LOCAL_MACHINE subtree:


  2. Select the Debugger value.
  3. On the Edit menu, click String.

    • To use the Windows debugger, type windbg -p %ld -e %ld.
    • To use Visual C++ 4.2 or earlier, type msvc -p %ld -e %ld.
    • To use Visual C++ 5.0 or later, type msdev.exe -p %ld -e %ld.
    • To use Dr. Watson, type drwtsn32.exe -p %ld -e %ld. You can also make Dr. Watson the default debugger by running this command:drwtsn32.exe -i.
  4. Choose OK and exit Registry Editor.
The new debugger is used the next time you log on.
NTAS Breakpoint NTS NTW debugref

Article ID: 121434 - Last Review: 12/04/2015 10:35:38 - Revision: 2.1

Microsoft Windows 2000 Server, Microsoft Windows 2000 Advanced Server, Microsoft Windows 2000 Professional Edition, Microsoft Systems Management Server 2.0 Standard Edition, Microsoft Windows NT Advanced Server 3.1, Microsoft Windows NT Advanced Server 3.1, Microsoft Windows NT Server 3.51, Microsoft Windows NT Server 4.0 Standard Edition, Microsoft Windows NT Workstation 3.1, Microsoft Windows NT Workstation 3.5, Microsoft Windows NT Workstation 3.51, Microsoft Windows NT Workstation 4.0 Developer Edition

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