Article ID: 111473
Article Last Modified on 10/14/2003
APPLIES TO
- Microsoft Macro Assembler 6.0 Standard Edition
- Microsoft Macro Assembler 6.0a
- Microsoft Macro Assembler 6.0b
- Microsoft Macro Assembler 6.1 Standard Edition
- Microsoft Macro Assembler 6.1a
- Microsoft Macro Assembler 6.11 Standard Edition
This article was previously published under Q111473
SYMPTOMS
A STRUCT declaration containing an ORG directive will change the current segment size when the -Sf switch is used and a listing file is produced with MASM 6.x.
CAUSE
When adding a first-pass listing (the -Sf switch) to the listing file, MASM's internal location counter is affected when the ORG directive is encountered within a STRUCT declaration. This location counter is ultimately used to determine segment size.
RESOLUTION
When declaring a STRUCT that contains an ORG directive, place the declaration outside of any open segments. Because this is a structure declaration rather than an actual instance, the structure does not have to be within a segment and can be placed outside all open segments where the location counter will not be adversely affected.
STATUS
Microsoft has confirmed this to be a problem in the Microsoft Macro Assembler (MASM) versions 6.x. We are researching this problem and will post new information here in the Microsoft Knowledge Base as it becomes available.
MORE INFORMATION
The following sample code illustrates this problem. When the structure is declared within the open data segment, the size of the data segment is increased. This can be viewed in the map file for the sample, as well as in the listing file. Move the structure declaration before the .DATA and .STACK directives to obtain the expected behavior.
An ORG directive is permitted in a structure declaration beginning with MASM version 6.0. This enables the generation of a template that can ease references to the internals of data structures that are predefined, for instance by the operating system, the operating platform, or a high-level language compiler.
For additional information about this MASM construct as well as sample code demonstrating its use, please see the following article(s) in the Microsoft Knowledge Base:
111474 PRB: Usage of an ORG Directive in a STRUCT Declaration
Sample Code
; Assemble options needed: -Fl -Sf -Fm
.MODEL SMALL,C
.386
NUMLINES EQU 25
NUMCOLS EQU 80
.STACK
.DATA
status STRUCT ; Move STRUCT declaration
org (NUMLINES - 2) * NUMCOLS * 2 ; before .DATA and .STACK
line1 db ? ; to work around problem.
attrib1 db ?
org (NUMLINES - 1) * NUMCOLS * 2
line2 db ?
attrib2 db ?
status ENDS ; end STRUCT declaration
msg db "Sample code", 13, 10, "$"
.CODE
.STARTUP
<WWBLOCKQUOTE>
mov dx, OFFSET msg
mov ah, 9
int 21h ; output string
.EXIT
Additional query words: 6.00 6.00a 6.00b 6.10 6.10a 6.11 6.1x buglist6.10 buglist6.10a buglist6.11 buglist6.00 buglist6.00a buglist6.00b
Keywords: KB111473
