32-Bit Flat Memory Model MASM Code for Windows NT
ID: Q94314
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The information in this article applies to:
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Microsoft Macro Assembler for MS-DOS, versions 6.00a, 6.00b, 6.10, 6.10a, 6.11
SUMMARY
The Microsoft Macro Assembler (MASM) versions 6.0a and later support
generating 32-bit flat memory model code through the .MODEL flat
directive. When combined with the CVTOMF and LINK32 utilities and the
KERNEL32.LIB library distributed with the Windows NT software
development kit (SDK) or the LINK utility and the KERNEL32.LIB library
distributed with Microsoft Visual C++ for Windows NT, MASM can
generate a 32-bit flat memory model application for the Windows NT
environment.
Because MASM version 6.0 does not properly support the _stdcall
convention, it cannot be used to generate applications for the Windows
NT environment.
MORE INFORMATION
Given some MASM code in a file named FLAT32.ASM where its entry point
is _start, to assemble this code into a 32-bit flat memory model
application for the Windows NT environment, perform the following four
steps:
- Place the .386 or .486 directive in the code prior to the .MODEL
flat, stdcall directive to ensure that the code and data segments
are correctly initialized for a 32-bit flat memory model
application.
- Assemble the source code using the following command:
ML /c flat32.asm.
The /c assembler option prevents the MASM from invoking the 16-bit
linker provided with MASM.
- For MASM 6.0a or 6.0b, use the CVTOMF utility provided with the
Windows NT SDK to convert the generated object files from OMF
format to COFF format. The command is as follows:
cvtomf flat32.obj
This step is unnecessary with MASM version 6.1 and later if you use
the /coff switch because it will produce a COFF format object file.
- Use the LINK32 utility provided with the Windows NT SDK or LINK
utility provided with Visual C++ for Windows NT to link the object
modules. Specify a path to KERNEL32.LIB. The command line is as
follows:
link32 -subsystem:console -entry:_start -out:flat32.exe
flat32.obj kernel32.lib
To create an executable module that contains symbolic debugging
information, add the -Zi switch to the assembler options (Step 2)
and add the following switches to the linker command line:
-debug:full -debugtype:cv.
If you are using LINK32 from the Windows NT SDK, do not use the
INCLUDELIB directive and do not place the starting label after the END
directive in the MASM code. The LINK32 utility provided with the
Windows NT SDK ignores the default library names in object files and
requires the -entry switch on the linker command line to specify the
starting address.
Windows NT does not support the MLX driver provided with MASM versions
6.0a and 6.0b. Also, Windows NT does not support the MS-DOS-extender
used by MASM versions 6.1 and 6.1a. Therefore, it may be necessary to
perform the assembly step on a machine running MS-DOS while the other
steps run on a machine running Windows NT. Another option is to
upgrade to MASM version 6.11.
The code below is a "Hello, world" application developed in assembler
to use the 32-bit flat memory model of Windows NT.
Sample Code
; Assemble options needed: /c
.386
.MODEL flat, stdcall
STD_OUTPUT_HANDLE EQU -11
GetStdHandle PROTO NEAR32 stdcall,
nStdHandle:DWORD
WriteFile PROTO NEAR32 stdcall,
hFile:DWORD, lpBuffer:NEAR32, nNumberOfBytesToWrite:DWORD,
lpNumberOfBytesWritten:NEAR32, lpOverlapped:NEAR32
ExitProcess PROTO NEAR32 stdcall,
dwExitCode:DWORD
.STACK 4096
.DATA
msg DB "Hello, world.", 13, 10
written DW 0
hStdOut DD 0
.CODE
_start:
INVOKE GetStdHandle,
STD_OUTPUT_HANDLE ; Standard output handle
mov hStdOut, eax
INVOKE WriteFile,
hStdOut, ; File handle for screen
NEAR32 PTR msg, ; Address of string
LENGTHOF msg, ; Length of string
NEAR32 PTR written, ; Bytes written
0 ; Overlapped mode
INVOKE ExitProcess,
0 ; Result code for parent process
PUBLIC _start
END
Additional query words:
kbinf 6.00a 6.00b 6.10 p_w32dev
Keywords :
Version : :6.00a,6.00b,6.10,6.10a,6.11
Platform :
Issue type :