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Q94314: 32-Bit Flat Memory Model MASM Code for Windows NT

Article: Q94314
Product(s): Microsoft Macro Assembler
Version(s): 6.00a,6.00b,6.10,6.10a,6.11
Operating System(s): 
Keyword(s): 
Last Modified: 04-MAY-2001

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The information in this article applies to:

- Microsoft Macro Assembler (MASM), versions 6.00a, 6.00b, 6.10, 6.10a, 6.11 
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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:

1. 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.

2. 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.

3. 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.

4. 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          :  
Technology        : kbMASMsearch kbAudDeveloper kbMASM611
Version           : :6.00a,6.00b,6.10,6.10a,6.11

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

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