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https://github.com/ratfactor/nasmjf

NASM port of JONESFORTH!
https://github.com/ratfactor/nasmjf

assembly-language assembly-x86 forth jonesforth nasm

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NASM port of JONESFORTH!

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= nasmjf - a NASM port of JONESFORTH



**MOVED!** Hello, I am moving my repos to http://ratfactor.com/repos/

and setting them to read-only ("archived") on GitHub. Thank you, _-Dave_



This is a fully-functioning Forth interpreter faithfully ported from the original

by Richard W.M. Jones:



https://rwmj.wordpress.com/2010/08/07/jonesforth-git-repository/



You can see the full original source in the `jonesforth/` directory in this repo.



Assemble and run `nasmjf` like so:



----

$ ./build.sh

$ ./nasmjf

JONESFORTH VERSION 1

20643 CELLS REMAINING

OK

: hello ." Hello world!" CR ;

hello

Hello world!

BYE

$

----



This repo is a port from the original GNU Assembler (GAS) implementation to

the Netwide Assembler (NASM). The biggest difference between the two assemblers

is AT&T-style GAS syntax vs. Intel-style NASM syntax. But I have made a couple

changes. The biggest one is that `nasmjf` loads the `jonesforth.f` source file

(containing the second half of the interpreter written in Forth) upon startup.



See "Loads Jones's FORTH source on start" below.



== Current status



It's done! It passes the original JONESFORTH tests. See

`test.sh` in the root of this repo.



== Why does this exist?



Check out the `devlog/log*.txt` text files. They're my rambling learning-in-public and

thinking "out loud" way of describing what I'm up to. The latest log will probably

give an idea of what I'm currently doing or what I've most recently completed.



I also wrote an article about my delightful process with this project:

http://ratfactor.com/assembly-nights



I also have a placeholder for future notes and rambling thoughts about the project here:

http://ratfactor.com/nasmjf



== Compiling and running



You'll need the NASM assembler, a linker such as `ld`, and a Linux computer

(JF relies on raw syscalls). And a sense of adventure.



To build the `nasmjf` executabe, run `build.sh`. (Or see what it does.)



Manually assemble and link like so:



----

$ nasm -f elf32 -g -o nasmjf.o nasmjf.asm

$ ld nasmjf.o -o nasmjf

$ rm nasmjf.o

----



Run by calling the executable you just compiled:



----

$ ./nasmjf

'A' EMIT

A

----



If you're going to use JONESFORTH for anything longer than a simple line or

two, I _highly_ recommend wrapping it in `readline` with the excellent `rlwrap`

(https://github.com/hanslub42/rlwrap) like so:



----

$ rlwrap ./nasmjf

----



Then you'll have line editing, history (up arrow lets you re-enter and edit the

last line), and even persistent history between Forth sessions!



== Loads Jones's FORTH source on start



The implementation of JONESFORTH is in two parts: an assembly language

"bootstrap" and additional essential word definitions written in FORTH.



This NASM contains a hard-coded path to the `jonesforth.f` FORTH source file

and reads it automatically when the interpreter starts. This is to make

starting and debugging the system easier and more convenient.



If you wish to disable or simply examine this change, search for lines with

comments containing the string `LOADJF`. You can comment out most of these

lines. A few will need to remain. Figuring out which is "left as an exercise

for the reader", as they say.



== GNU Debugger



I've made heavy use of the GNU Debugger to fix mistakes, understand what

my program is doing, and in these early stages, it's nearly the only way

to tell what's happening in the program at all.



I'm assembling with DWARF2 debugging info. See the `r` script for params.



See `gdb.script` for current defaults I'm using.



Show stuff:



    maint info sections     # memory sections

    info addr word_buffer   # address of symbol (label/var/func)

    info sym 0x804c608      # reverse of info addr, symbol at addr

    info var buff           # list (with addr!) of symbol names w/ "buff"

    info var                # list ALL symbols

    info var var_           # list all symbols that start with "var_"



Print values (register,  label, literal numbers (handy as base converter)



    p 0x50                  # prints 80

    p/x 80                  # prints 0x50

    p/x (int)some_label     # show 4 bytes (32b) of data at some_label in hex

    p/x &some_label         # ADDRESS of some_label



Print value at memory location



    x/x &some_label         # show a byte of data at some_label in hex

    x/s &some_label         # show a string at some_label

    x/4x &some_label        # show four consecutive bytes



Set temporary break and jump to location (by label)



    tbreak docol

    jump docol



Create GDB commands



    define foo

        p $arg0

        p $arg1

    end



== GNU Screen



See the file `screenrc` in this repo to see the current convenience setup.

In short, I've got a GDB session and Vim session open in separate windows

so I can quickly toggle between them. Anything outside of those two

applications is best done in a new window to keep from accidentally closing

one of the two main windows.



* `C-j C-j` toggle between main windows

* `C-j c` create a new window with a shell

* `C-j H` start (or stop) logging window (not actually what I want)

* `C-j h` save hardcopy of scrollback buffer (actually what I want)

* `C-j ?` help (show other shortcuts)



I'm using the hardcopy feature to help me record running each milestone of

progress in GDB sessions to test and document (and celebrate!) the work.



An alias called `jf` starts my two-windowe session like so:



----

alias jf='screen -c nasmjf/screenrc'

----



== .vimrc



My whole setup on this machine is dedicated to this project.

Here's the entirety of my current `.vimrc`:



----

set tabstop=8 softtabstop=0 expandtab shiftwidth=4 smarttab

colorscheme elflord

" simple buffer switching mappings for a handful of files

nnoremap  :bn

nnoremap  :bp

" my eeepc chugs when trying to apply highlighting to this large asm file

au BufRead jonesforth.S set syntax=text nowrap

au BufRead nasmjf.listing set nowrap

let mapleader = ","

----



== PUBLIC DOMAIN



Because Richard Jones released his work as public domain, it's only right

that I should release my port also as public domain. So here's the license:



I, the copyright holder of this work, hereby release it into the public domain.

This applies worldwide.



In case this is not legally possible, I grant any entity the right to use this

work for any purpose, without any conditions, unless such conditions are

required by law.