JWasm

Index

JWasm

1. About JWasm
2. Comparison of MASM-Style Assemblers
3. Source Samples
4. User Feedback
5. Roadmap
6. Download

1. About JWasm

JWasm is a free MASM-compatible assembler with these features:

native support for output formats Intel OMF, MS Coff (32- and 64-bit), Elf (32-and 64-bit), Bin and DOS MZ.
precompiled JWasm binaries are available for DOS, Windows and Linux. For OS/2 and FreeBSD, makefiles are supplied.
Instructions up to AVX are supported.
JWasm is written in C. The source is portable and has successfully been tested with Open Watcom, MS VC, GCC and more.
As far as programming for Windows is concerned, JWasm can be used with both WinInc and Masm32. Since v2.01, it will also work with Sven B. Schreiber's ancient WALK32.
C header files can be converted to include files for JWasm with h2incX.
JWasm's source code is released under the Sybase Open Watcom Public License, which allows free commercial and non-commercial use.

Further documents:: Readme.

JWasm started as a fork of Open Watcom's Wasm in March 2008. Today, the part of Wasm source lines still contained in JWasm is approximately 20%.

2. Comparison of MASM-Style Assemblers

There are - at least - 4 assemblers available which (partially) understand MASM syntax:

MASM, the original, Microsoft
TASM, Borland
POASM, part of PellesC
WASM, part of Open Watcom. [Wasm is neither Masm v6 nor v5 compatible, but it understands both Masm v5 and v6 syntax partially. Additionally it knows how to encode instructions implemented in newer cpus.]

JWasm compared with	Advantages	Disadvantages
MASM	JWasm is free, no artificial license restrictions, can be used to create binaries for any OS.	None.
	JWasm's source is open. Hence JWasm is able to run - natively - on Windows, DOS, Linux, FreeBSD and OS/2.
	More output formats supported (Bin, ELF).
	optionally very small object modules can be created
	better support for Open Watcom, for example the register-based calling convention
	JWasm is faster than Masm.
TASM	JWasm is available. TASM isn't legally available. And LZASM, which is sort of a TASM clone, understands IDEAL mode only.	TASM additionally understands IDEAL mode. This was a big advantage compared to MASM v5.1, but compared to MASM v6 syntax there are no benefits anymore.
	JWasm has full support for STRUCTs and UNIONs. TASM has severe limitations and bugs in this area.
	JWasm supports virtually all more recent MASM features (PROTO, INVOKE, hll directives, ... ), most of which TASM won't understand.
	JWasm supports instructions of recent Intel CPUs, TASM is behind.
POASM	JWasm is open source	None.
	JWasm additionally supports output in OMF, ELF and binary format
	JWasm supports 16-bit and segmented memory models. POASM understands FLAT only.
	Unlike POASM, JWasm is compatible with MASM's implementation of macros.
	POASM lacks the ability to create a listing file.
WASM	JWasm's macro capabilities are ways better than Wasm's.	Wasm's cmdline is more compatible with Open Watcom tools
	JWasm fully supports Masm v6 syntax. In Wasm, most of the additions done in Masm v6 are missing.
	Besides OMF, JWasm supports COFF, ELF and binary output formats.
	JWasm supports 64-bit.

3. Source Samples

Note: all source samples are included in the precompiled binary packages.

DOS	console	"Hello world", COM format
DOS	console	"Hello world", DPMI16
DOS	console	"Hello world", DPMI32
DOS	console	Switches to 64-bit and back
OS/2 16	console	"Hello world"
OS/2 32	console	"Hello world"
Win16	GUI	"Hello world"
Win32	console	"Hello world"
Win32	console	"Hello world", uses WinInc
Win32	GUI	"Hello world", uses Masm32
Win32		Dll
Win32	console	"Hello world", PE binary without linker
Win32	console	demonstrates how to use Unicode
Win64	GUI	"Hello world", MessageBox
Win64	GUI	"Hello world", Window
Win64	GUI	"Hello world", with SEH support (Masm comp.)
Win64	GUI	"Hello world", with SEH support (JWasm only)
Win64	console	"Hello world", uses WinInc v2+ (JWasm only)
Win64	console	exception handling, uses WinInc v2+ (JWasm only)
Win64	console	uses MSVCRT and WinInc v2+ (JWasm only)
Win32/Win64	console	"bimodal" source (JWasm only)
Linux 32	console	"Hello world", using syscalls
Linux 32	console	"Hello world", using libc
Linux 32	console	ncurses demonstration
Linux 32	GUI	"Hello world", X application
Linux 64	console	"Hello world", using syscalls
FreeBSD 32	console	"Hello world", ELF binary without linker
Mixed 16		hll calling assembly
Mixed 16	console	assembly calling CRT
Mixed 32		hll calling assembly
Mixed 32	console	assembly calling CRT
Mixed 32	console	Shows how to use FPU and CRT math functions
Mixed 32	console	html-to-text converter
Mixed 32	console	masm-to-html converter
Mixed 32	GUI	"Hello world", GTK+ application

4. User Feedback

JWasm uses SourceForge for user feedback:

5. Roadmap

Pipeline for next releases:

CodeView V8 symbolic debugging information for output format COFF.
DWARF symbolic debug information for output format ELF.

6. Downloads

		Binary Windows	Binary Linux	Binary DOS	Source
JWasm v2.06e	07/22/2011	JWasm206bw.zip	JWasm206bl.zip	JWasm206bd.zip	JWasm206s.zip	change log
JWasm v2.07 preliminary	11/03/2011	JWasm207bw.zip	JWasm207bl.zip			change log

List of all JWasm versions available for download

Helper tools

WRC - OW resource compiler v1.9	05/2010	Win32	wrc.zip (binary)
WDW - OW debugger for NT/XP v1.8	02/2009	Win32	wdw.zip (binary)
PE - PE, COFF, AR dumper	01/13/2010	Win32, DOS	pe.zip (binary & source)
Agner Fog's ObjConv v2.09 - Object format converter + Disassembler	08/2009	DOS	objconv.zip (binary)
MS OMF Linker v5.60	12/1994	Win32, DOS	lnk563.exe
MS NMake v1.5	1994	Win32	nmake15.exe