JWasm
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1. About
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 SSE4.2 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 Win32Inc 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.
JWasm is a fork of Open Watcom's WASM.
More details.
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2. User Feedback
JWasm uses SourceForge for user feedback:
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3. JWasm compared with other MASM-like Assemblers
There are - at least - 4 assemblers available which (partially) understand MASM syntax:
- MASM, the original, Microsoft
- 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.
- TASM, Borland
- POASM, part of PellesC
| JWasm compared with |
Advantages |
Disadvantages |
| MASM |
JWasm is free, no artificial license restrictions, can be used to create binaries for any OS. |
None. |
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JWasm is open source, forget the annoying MASM bugs ... |
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More output formats supported (Bin, ELF). |
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optionally very small object modules can be created |
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better support for Open Watcom, for example the register-based calling convention |
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JWasm is faster than Masm. |
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| WASM |
JWasm is a fork of Wasm. There was a huge amount of additions and bugfixes
( this list was a changelog for the initial JWasm version 1.70. There were a
lot of other additions since then )
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Wasm's cmdline is more compatible with Open Watcom tools |
| 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. |
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JWasm has full support for STRUCTs and UNIONs. TASM has severe limitations and bugs in this area. |
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JWasm supports virtually all MASM v6 features (PROTO, INVOKE, hll directives, ... ), most of which TASM won't understand. |
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JWasm supports instructions up to SSE4, TASM is behind. |
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| POASM |
JWasm is open source |
None. |
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JWasm additionally supports output in OMF, ELF and binary format |
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JWasm supports 16-bit and segmented memory models. POASM understands FLAT only. |
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JWasm is compatible with MASM's implementation of macros. POASM isn't. |
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POASM lacks the ability to create a listing file. |
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4. Source Samples
| 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 Win32Inc |
| 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 Win32Inc v2+ (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 |
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5. Roadmap
Pipeline for next releases:
- symbolic debug info for output format ELF.
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6. Downloads
List of all versions available for download
Helper tools
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