Gluttonous

MetaRuby

Posted by kev Sat, 15 Oct 2005 02:54:00 GMT

Eric Hodel

Once upon a time…

• Eric and Ryan were hacking some Ruby related C
• And it sucked
*

MetaRuby

• Will implement Ruby in Ruby
  • Core libarireis, parser, interpeter

MetaRuby Architecture

• Parser
• Interpeter
• GC
• …

Why?

• Writing Ruby internals in C requries mental context switch every time you change bwetween RUby and C

Example of C code vs Ruby code.

• More Familiar
• More approachable
• Less to do
  • No NULL termination
  • No tainting or freezing

Inspirationsal Projects

• Sqeak Smalltalk
• Self
• Pascal, Modula-2, Oberon by Wirth
• All of these are written in themselves

Related Projects

• Matju’s MetaRuby
• YARV
• JRuby

Matju’s MetaRuby

• Different goal much more complex
• Abstracted core classes

YARV

• Ruby interpreter replacement

Rubidium

• Ruby interpreter replacement
• Rubidium is an optimizing Ruby interpreter

Rubytests

• Unit tests for Ruby
• Not comprehensive enough for our goals
• Not much work making it more complex

JRuby

• A 1.8.2 compatible Ruby interpreter
• Most builtin Ruby classes provided
• Support for interfacing and defining Java classes in Ruby
• Uses Rubytests

Current Work

Methodology

• Generate a stubbed class to overlay
• Drive unit tests to failure
  • Identify core methods (primitives) that have to exist
  • Fix bad tests that pass despite no implementation
• Drive all tests to green
  • Hack, hack, hack

Passing Tests

• TrueClass, FalseClass and NilClass
• Time
• Range
• NilClass
• Array
• String

Overlaid Classes

These classes overlay their core classes using Ruby’s C allocation and initialization methods replacing as many methods as possible

• TrueClass
• NilClass
• Array
• String

Replaced Classes

• Time
• Range
• Hash

Rubytests

• Stale
  • Mostly tests Ruby 1.6 language features
• Low test coverage
• Not fully converted to Test::Unit
  • Way too much code from pre-testunit

Test::Unit

• Needs lots of methods to work
• Too complicated to refactor
• Working on core classes is hard

Future Work

Primitives

• Will be automatically translated to C
• What is a primitive?
  • Implement as much as possible in Ruby
  • Whatever is left becomes a primitive ** Unless we can break it down
• Choosing primitives is a discovery process

Ruby2c Translation

• Ryan will cover this a lot more
• Only necessary for primitives

Memory Allocation (Objects)

• Currently Array and String sit on top of C Ruby
• Write object allocation in pure Ruby using current memory system for all objects
• Then we will replace the memory system with a pure Ruby system

Replace core ruby library

• Works!
• Well.. kind of..
• Compiles
• Links!
• Segfaults!
• Needs alot of ping pong

Far Future Work

h5. The Groveling Commences

Parser

• Ripper is our best target
• Almost entirely Ruby already
• Just one file is in C, which we can rewrite

Object System & Garbage Collector

• Steal ideas from Sqeuak Smalltalk, Self, current Ruby
• In theory it should be easy to do
• In reality it will be hard to do well
• We’d love someone to work on this

Interpreter

• YARV or eval.c (Ruby 1.8)?
• Rubidium?
• Needs to we written in Ruby
• We’d love someone to work on this

C Extensions & C Standard Library

• Why are you writing pure C anyways?
  • Use RubyInline or DL
• Probably need Ruby/C compatability stubs
  • Easy to generate
• Will need to follow current Ruby/C naming conventions

Array#fill

Eight ways to call

• array.fill(obj)
• array.fill(obj, start[, length])
• array.fill(obj.range)
• array.fill {|index| block }
• array.fill(start…

“foo”.sub(/f(o)o/) { $1 }

• $1 is a “magick” read only global
• $1 can’t be set from pure Ruby
• So the interpreter needs to help us out
• Applies to all match variables

String#split

• Easy
• “a b”.split # => [‘a’, ‘b’]
• “a|b”.split # => [

• “a1b”.split(/*\d)/) # => [‘a’,’1’,’c’]

• Hard

Time.rb Needs Metal

• Easy
  • the_time.month
  • thetime.tof
  • etc
• Hard
  • Time.now requries calling libc’s gettime method
  • Currently we have libcwrap.rb that uses RubyInline to call into C funcitons