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Q111593: BUG: DPMI Function 0203h Does Not Report Error

Article: Q111593
Product(s): Microsoft Windows Software Development Kit
Version(s): 3.1
Operating System(s): 
Keyword(s): 
Last Modified: 21-FEB-2002

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The information in this article applies to:

- Microsoft Windows Software Development Kit (SDK) 3.1 
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SYMPTOMS
========

Using the MS-DOS Protected Mode Interface (DPMI) function 0203h (set processor
exception handler vector) to set an exception handler does not report an error
(carry flag set) if the selector:offset pair is invalid.

RESOLUTION
==========

The pointer to the exception handler must be validated with other means if it is
necessary to check the pointer for validity. Other means of checking a code
pointer for validity include using IsBadCodePtr() or the LAR (load access
rights) protected-mode CPU instruction.

STATUS
======

Microsoft has confirmed this to be a bug in Windows version 3.1. We are
researching this problem and will post new information here in the Microsoft
Knowledge Base as it becomes available.

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

The problem with DPMI function 0203h can be illustrated with the following code
segment:

     mov     edx, dword ptr BogusOffset
     mov     cx, word ptr BogusSelector
     ; Set Processor Exception Handler Vector
     mov     ax, 203h
     mov     bx, 7
     int     31h
     jc      Error       ; never jumps to Error

REFERENCES
==========

The IsBadCodePtr() function is documented in the Windows 3.1 SDK "Programmer's
Reference, Volume 2: Functions" manual. The LAR instruction is documented in the
Intel 386 or 486 "Programmer's Reference" or in "Microsoft's 80386/80486
Programming Guide" by Microsoft Press.

Additional query words: buglist3.10 3.10

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Keywords          :  
Technology        : kbAudDeveloper kbWin3xSearch kbSDKSearch kbWinSDKSearch kbWinSDK310
Version           : :3.1

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