Windows Development with MASM

In this post, I’ll walk through the steps required to bootstrap your development experience against the Win32 API using the Microsoft’s Macro Assember.

Prerequisites

Downloading the package from the masm32.com site will be everything that you need to produce applications using assembly language. It not only includes the assember ml, but also includes all of the library, include files and linker for you.

Test program

Here’s the code to present a message box.

; #######################

  .386
  .model flat, stdcall
  option casemap :none   ; case sensitive

; #######################

  include windows.inc
  include user32.inc
  include kernel32.inc

  includelib user32.lib
  includelib kernel32.lib

; #######################

.data

  szTitle  db "Your message", 0
  szMsg    db "First message box", 0

.code

start:

  invoke MessageBox, 0, offset szMsg, offset szTitle, MB_OK
  invoke ExitProcess, 0

end start

invoke goes a long way to cleaning up how any assembly program that is sub-routine heavy looks. The include files already do the externing of library symbols so that your code doesn’t need to explicitly declare that you’re using a particular function.

Assembling and linking

Now that you’ve got your source file, hello.asm you can produce an object file and executable with the following:

C:\src> ml.exe /IC:\masm32\include /coff hello.asm /link /SUBSYSTEM:WINDOWS /LIBPATH:C:\masm32\lib

You can see that not only assembler switches are passed, but also linker switches which means you’re assembling and linking all in one step.

Conclusion

The bundle for masm32 that this article refers to is great in the amount of code that it offers you, but the provided assembler is well-dated. Microsoft have been keeping masm updated from their website with 64 bit versions available with their development tools.