Microsoft KB Archive/137199

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PRB: Debuggers Cannot Reliably Use Debug Register Breakpoints

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Q137199

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The information in this article applies to:


 * Microsoft Win32 Software Development Kit (SDK), version 4.0
 * Microsoft Windows 2000 Advanced Server
 * Microsoft Windows 2000 Server
 * Microsoft Windows 2000 Professional

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SYMPTOMS
Debug register breakpoints are breakpoints that trigger on write or read of a specific memory location. If you use debug register breakpoints in application debuggers such as CodeView, Visual C++, or Windbg, other applications in the system could fault.

CAUSE
Debug registers are not saved and restored on a per application basis in Windows 95; they are global to the system.

A debug register running at the same address (but in another memory context) could trigger that debug breakpoint. Because there may not be a debugger registered to handle the breakpoint in the second application, Windows 95 interprets this as an unhandled exception. In most cases, this causes Windows 95 to terminate the second application, even though it had nothing to do with the problem.

RESOLUTION
To work around this problem, use a system level debugger such as Soft-ICE or WDEB386, or avoid using debug register breakpoints.

STATUS
This behavior is by design.

Additional query words: 4.00 win95fest

Keywords : kbOSWinNT400 kbOSWin2000 kbSDKWin32 _IK

Issue type :

Technology : kbwin2000AdvServ kbwin2000AdvServSearch kbwin2000Serv kbwin2000ServSearch kbwin2000Search kbwin2000ProSearch kbwin2000Pro kbWin32SDKSearch kbAudDeveloper kbSDKSearch kbWinAdvServSearch kbWin32sSearch kbWin32SDK400