DOCUMENT:Q40784  26-JUN-2001  [utilities]
TITLE   :CodeView Does Not Work with Grouped Code Segments
PRODUCT :Microsoft Programming Utilities
PROD/VER::2.2,3.0,3.11,3.12,3.14,3.5,4.0,4.01,4.05,4.1
OPER/SYS:
KEYWORDS:kb16bitonly

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - Microsoft CodeView for MS-DOS, versions 2.2, 3.0, 3.11, 3.14, 4.0, 4.01, 4.05, 4.1 
 - Microsoft CodeView for OS/2, versions 2.2, 3.0, 3.11, 3.12, 3.5 
-------------------------------------------------------------------------------

Using the Microsoft Macro Assembler (MASM), it is possible to
associate various segments into a group; DGROUP is an example of this
technique. Grouped data or stack segments do not affect CodeView but
CodeView does not recognize grouped code segments. The program will
run correctly under CodeView but none of the CodeView functions will
be available on the second and subsequent segments in the code group.

The sample code below illustrates this behavior. Once the program
executes into the _TEXTB segment, all CodeView functionality is lost.
You cannot set any breakpoints or single step through the _TEXTB code.
Any attempt to single trace into _TEXTB will result in CodeView
running all the code in _TEXTB as if you had specified a go or a step

Sample Code
-----------

   ; Assembler options needed: /Zi

           DOSSEG
   _TEXT   GROUP   _TEXTA, _TEXTB         ; Code group _TEXT

   _DATA   SEGMENT WORD PUBLIC 'DATA'
   msg     DB      "Hello, world.", 13, 10, "$"
   _DATA   ENDS

   _TEXTA  SEGMENT WORD PUBLIC 'CODE'     ; First code segment - this
           ASSUME  cs:_TEXT,ds:_DATA      ;  code may be traced as
   start:  mov     ax, _DATA              ;  expected.
           mov     ds, ax
           call    FAR PTR SayHi
           mov     ax, 4C00h
           int     21h
   _TEXTA  ENDS

   _TEXTB  SEGMENT WORD PUBLIC 'CODE'     ; You cannot trace through
   SayHi   PROC                           ;  this code.
           mov     ah, 9h
           mov     dx, OFFSET msg
           int     21h
           ret
   SayHi   ENDP
   _TEXTB  ENDS

           END     start

Additional query words: kbinf 2.20 3.00 3.50 4.10

======================================================================
Keywords          : kb16bitonly 
Technology        : kbAudDeveloper kbCodeView kbZNotKeyword3 kbCodeView220DOS kbCodeView300DOS kbCodeView311DOS kbCodeView314DOS kbCodeView400DOS kbCodeView401DOS kbCodeView405DOS kbCodeView410DOS kbCodeView220OS2 kbCodeView300OS2 kbCodeView311OS2 kbCodeView312OS2 kbCodeView350OS2
Version           : :2.2,3.0,3.11,3.12,3.14,3.5,4.0,4.01,4.05,4.1

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

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 2001.