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Q74925: FIX: A1010 from Unclosed Segment in MASM @ShowStr Macro

Article: Q74925
Product(s): Microsoft Macro Assembler
Version(s): MS-DOS:6.0
Operating System(s): 
Keyword(s): 
Last Modified: 04-MAY-2001

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

- Microsoft Macro Assembler (MASM), version 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The Microsoft Macro Assembler (MASM) version 6.0 includes a predefined macro in
DOS.INC called @ShowStr that displays a $-terminated string. When the argument
to @ShowStr is a string literal and there are no segment directives or ends
directives following the occurrence of @ShowStr, the assembler will generate the
following error:

  fatal error A1010: unmatched block nesting: _DATA

RESOLUTION
==========

To work around this problem, make sure that a simplified segment directive or
ends directive follows the @ShowStr macro.

STATUS
======

Microsoft has confirmed this to be a problem in MASM version 6.0. This problem
was corrected in MASM version 6.0a.

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

When @ShowStr is passed a string literal, the macro generates the following
code:

     sseg    TEXTEQU @CurSeg        ; save current segment
     .DATA                          ; change segment
     msg     BYTE    ofset, "$"     ; terminate string with a '$'
     sseg    SEGMENT                ; restore segment
     mov     dx,     OFFSET msg
     mov     ah,     9
     int     21h                    ; display '$' terminated string

The line "sseg SEGMENT" restores the segment but the macro never closes the
segment; it relies on the user subsequently closing the segment with the
appropriate ends directive or by opening another segment with a simplified
segment directive. If the segment is left open, an A1010 error is generated.

In the sample code below, @ShowStr is in a segment started with .CODE. In the
macro expansion, that segment is ended and the next segment begun with .DATA.
The code segment is restored with the statement _TEXT SEGMENT. This segment is
not closed in the macro or in the subsequent code, so the A1010 error is
produced. The error can be eliminated by uncommenting either of the commented
lines.

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

  ; Assemble options needed: none

  .MODEL small

  INCLUDE dos.inc

  .STACK 4096
  .CODE
      .startup
      @ShowStr "Hello"
      .exit 0
  ; uncomment one of the following lines to work around the problem
  ; _TEXT ENDS
  ; .DATA

  END

Additional query words: 6.00 buglist6.00 fixlist6.00a

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM600
Version           : MS-DOS:6.0
Solution Type     : kbfix

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

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