JWasm
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1. About
JWasm is a MASM v6 compatible assembler. It's a fork of Open Watcom's WASM
and released under the
Sybase Open Watcom Public License, which allows free
commercial and non-commercial use. JWasm is written in C, source code is open.
JWasm Features:
- JWasm natively supports output formats Intel OMF, MS Coff, Elf, 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 SSSE3 are supported.
- The JWasm 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.
- C header files can be converted to include files for JWasm with h2incX.
More details.
2. User Feedback
JWasm uses SourceForge for user feedback:
3. JWasm compared with other MASM-like Assemblers
There are - at least - 4 assemblers available which (partially) understand MASM syntax:
- MASM, the original from Microsoft
- WASM, part of Open Watcom
- TASM, from 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. |
JWasm's debug information is limited |
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JWasm is open source, forget the annoying MASM bugs ... |
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ELF output format is supported. |
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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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Since v1.9, 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.
[Wasm isn't Masm v6 compatible. It's also not really Masm v5 compatible.
It understands both Masm v5 and v6 syntax partially.
Additionally it knows how to encode instructions implemented in newer cpus.]
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None |
| 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 SSSE3, TASM is behind. |
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| POASM |
JWasm is open source |
JWasm (at least v1.xx) doesn't support 64bit. |
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JWasm supports output in OMF 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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4. Samples
| A Win32 console sample program for JWasm |
;--- Win32 "hello world" console application
.386
.MODEL FLAT, stdcall
option casemap:none
STD_OUTPUT_HANDLE equ -11
WriteConsoleA proto :dword, :dword, :dword, :dword, :dword
GetStdHandle proto :dword
ExitProcess proto :dword
.CONST
szString db 13,10,"hello, world.",13,10
LSTRING equ $ - szString
.CODE
main proc
local dwWritten:dword
local hConsole:dword
invoke GetStdHandle, STD_OUTPUT_HANDLE
mov hConsole,eax
invoke WriteConsoleA, hConsole, addr szString, LSTRING, addr dwWritten, 0
xor eax,eax
ret
main endp
;--- entry
mainCRTStartup proc c
invoke main
invoke ExitProcess, eax
mainCRTStartup endp
END mainCRTStartup
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DOS COM Sample
DOS DPMI16 Sample
DOS DPMI32 Sample
DOS Sample how to switch to 64-bit
OS/2 16bit Console Sample
OS/2 32bit Console Sample
Win16 GUI Sample
Win32 console Sample (Win32Inc)
Win32 GUI Sample (Masm32)
Win32: create PE binary without linker
Win64 MessageBox Sample
Win64 GUI Sample
Win64 GUI Sample with SEH support (Masm comp.)
Win64 GUI Sample with SEH support (JWasm only)
Linux Sample using syscalls
Linux Sample using libc
Linux X GUI Sample
Linux 64-bit Sample using syscalls
5. Roadmap
Pipeline for next releases:
- support for 64-bit.
- improve debug info output (type information).
6. Downloads
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