Microsoft KB Archive/94587

= FIX: DUP Behavior Different with Span-Dependent Value =

Article ID: 94587

Article Last Modified on 10/16/2003

-

APPLIES TO


 * Microsoft Macro Assembler 6.0 Standard Edition
 * Microsoft Macro Assembler 6.0a
 * Microsoft Macro Assembler 6.0b

-



This article was previously published under Q94587



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: kbfix KB94587

-

[mailto:TECHNET@MICROSOFT.COM Send feedback to Microsoft]

© Microsoft Corporation. All rights reserved.