FreeForth2

Derived from FreeForth by Christophe Lavarenne (1956-2011)

FreeForth2 offers a novel, lightweight Forth for x86 Linux that deftly blends assembly and Forth.

Features

FreeForth2 inherits its most distinctive features from FreeForth.

• interactivity through compiled anonymous functions (no separate interpret mode)
• macros generate inline x86 code
• top two stack elements use registers
• register renaming means zero-cost swap
• tail-call optimized to jump
• allows multiple entry-points to a function
• built-in help system

New Features

FreeForth2 improves usability, Linux integration, and quality controls.

• stat, mmap, getenv, getpid, getppid, system
• turnkey support
• simple locals
• segfault handler
• see disassembles words - Improved! resolves calls/jumps and handles inline strings
• simple approach to arguments
• library search path
• debug compiler makes verbose words
• alternate versions of conditionals use Booleans on the stack
• pictured numeric output
• unit tests
  • with optional compat.ff, passes 90% of the core words tests from the Forth 2012 test suite

Changes from FreeForth

• interactive input automatically terminated (closing ; assumed)
• quoted literals may contain spaces
• abandoned windows support
• requires explicit conditions before IF
  • avoids source of faulty assumptions (see criticism below)
• features separated into files in lib
• leading backquote for hiding headers replaced with :. pvt and hidepvt

Docs

• Christophe Lavarenne's writings about the original FreeForth with some notes pointing out differences in FreeForth2
  • FreeForth Home
  • FreeForth Primer
  • FreeForth Code Generation
• Exploration of FreeForth criticism: Criticism.md

Dependencies

• GCC toolchain and 32-bit libraries
  • For example, on Ubuntu LTS run sudo apt install build-essential gcc-multilib
• flat assembler, a.k.a. fasm: https://flatassembler.net/
  • Likely available in your Linux distro, e.g., sudo apt install fasm

Build

• run make which should create ff

Install

• run make install to install ff in $HOME/.local/bin
  • supporting files install to $HOME/.local/share/ff
  • to install to a different directory, set PREFIX
    • e.g., make PREFIX=/opt install

Library Search Path

• Interactive ff uses files like ff.ff and ff.help at runtime
• by default it searches:
  • .
  • lib
  • $HOME/.local/share/ff
  • /usr/local/share/ff
• insert directories into the search path with the environment variable FFPATH
  • e.g., export FFPATH=/opt/local/ff:/opt/ff

Building a turnkey binary

• NB. the source should have a main word
• run ff with -f for each source file and -f mkimage at the end
  • mkimage exports the dictionary to dict and compiled code to cmpl
• run make fftk
  • this assembles fftk.asm which includes dict and cmpl
• rename fftk as desired

$ cat cat.ff
needs mmap.ff
mkmm m
: ok?   dup $FF | 1+ drop 0= IF strerror rdrop ;THEN drop ;
: cat   m mmapr ok? m @ m mm.sz+ @ type m munmap 2drop ;
: main  0 argc 1- TIMES 1+ dup argv cat REPEAT ;
$ ./ff -f cat.ff -f mkimage.ff
$ make fftk
fasm fftk.asm fftk.o
flat assembler  version 1.73.27  (16384 kilobytes memory)
3 passes, 23484 bytes.
ld -m elf_i386 -lc --dynamic-linker=/lib/ld-linux.so.2 -s -o fftk fftk.o
$ mv fftk ffcat
$ ./ffcat cat.ff
needs mmap.ff
mkmm m
: ok?   dup $FF | 1+ drop 0= IF strerror rdrop ;THEN drop ;
: cat   m mmapr ok? m @ m mm.sz+ @ type m munmap 2drop ;
: main  0 argc 1- TIMES 1+ dup argv cat REPEAT ;