KnowledgeBase Archive

An Archive of Early Microsoft KnowledgeBase Articles

View on GitHub

Q77078: FIX: Whitespace Character Must Precede DUP Operator

Article: Q77078
Product(s): Microsoft Macro Assembler
Version(s): MS-DOS:6.0,6.0a,6.0b
Operating System(s): 
Keyword(s): 
Last Modified: 06-MAY-2001

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

- Microsoft Macro Assembler (MASM), versions 6.0, 6.0a, 6.0b 
-------------------------------------------------------------------------------

SYMPTOMS
========

When using the DUP operator in the Microsoft Macro Assembler (MASM), you must
place a whitespace character before the DUP operator if using the "?" operator.
If no whitespace is present, no error message is produced by the assembler, and
incorrect code will be generated. The assembler will generate one data item for
the specified type, initialized to the value of the repeat size for the DUP
operator.

RESOLUTION
==========

To work around the problem, place a space between the repeat size and the DUP
operator. Initializing the variable will cause a syntax error to be generated.

STATUS
======

Microsoft has confirmed this to be a problem in MASM version 6.0, 6.0a, and
6.0b. This problem was corrected in MASM for MS-DOS version 6.1.

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

The code example below generates a listing file that shows the size generated
for the respective DUP statements. It can be seen that the first DUP operation
generates 4 data bytes; however, the second generates 1 data byte initialized to
4.

The assembler has problems parsing this statement because the DUP operator begins
with a letter (d), which is a valid radix suffix.

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

  ; Assemble options needed: /Fl

  .MODEL small
  .STACK 4096

  .DATA
  a       DB 4 DUP(0)
  size_a  DB SIZEOF a
  b       DB 4DUP(?)
  size_b  DB SIZEOF b

  .CODE
  start:
     mov ax, 4C00H
     int 21H      ; Terminate Process
  END start

Additional query words: 6.00 6.00a 6.00b buglist6.00 buglist6.00a buglist6.00b fixlist6.10

======================================================================
Keywords          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM600 kbMASM600a kbMASM600b
Version           : MS-DOS:6.0,6.0a,6.0b
Solution Type     : kbfix

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

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.