Article: Q94587
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
========
In Microsoft Macro Assembler (MASM) versions 6.0, 6.0a, and 6.0b, if the size of
a DUP directive depends on the difference between the values of two labels (a
span-dependent value), the assembled code differs from that produced by previous
MASM versions.
CAUSE
=====
The size of the DUP depends on label values that are not yet determined in the
first assembly pass.
RESOLUTION
==========
Modify the code to remove span-dependent values in a DUP directive in code
assembled with MASM versions 6.0, 6.0a, or 6.0b.
STATUS
======
Microsoft has confirmed this to be a problem in MASM versions 6.0, 6.0a, and
6.0b for MS-DOS and OS/2. This problem was corrected in MASM version 6.1 for
MS-DOS.
MORE INFORMATION
================
This problem usually occurs when a forward reference occurs between the two
labels. The assembler adds padding bytes for the forward reference and
eliminates these bytes during a subsequent assembly pass. When this occurs, the
second label has a larger value during the first assembly pass than it does in
subsequent passes.
The sample code below demonstrates this behavior.
Sample Code
-----------
; Assemble options needed: none
tst1 SEGMENT para public
ASSUME cs:tst1
start:
jmp SHORT forward
forward:
mov ax, 4C00h
int 21h
tst1 ENDS
count = offset forward - offset start
tst2 SEGMENT para public
DB count DUP (2) ; This assembles as DUP 10 in MASM versions 6.0,
; 6.0a, and 6.0b. It assembles as DUP 2 in MASM
; versions 5.1 and 6.1.
xxx DB 1
tst2 ENDS
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
=============================================================================