Ecosyste.ms: Awesome

An open API service indexing awesome lists of open source software.

Awesome Lists | Featured Topics | Projects

https://github.com/attila-lendvai/maru

Maru - a tiny self-hosting lisp dialect
https://github.com/attila-lendvai/maru

bootstrap-process bootstrapping lisp maru self-hosted self-hosting sexpression-language

Last synced: 24 days ago
JSON representation

Maru - a tiny self-hosting lisp dialect

Awesome Lists containing this project

README 

        
# Maru



## What



Maru is a programming language. It's a

[self-hosting](https://en.wikipedia.org/wiki/Self-hosting_(compilers)),

yet tiny [lisp](https://en.wikipedia.org/wiki/Lisp_(programming_language))

dialect: a symbolic expression evaluator that can compile its own implementation to

[machine code](https://en.wikipedia.org/wiki/Machine_code),

in about 2000 LoC altogether.



> Maru is in particular trying to be malleable at the very lowest levels,

> so any special interest that cannot be accommodated easily within the common

> platform would be a strong indicator of a deficiency within the platform

> that should be addressed rather than disinherited. (Ian Piumarta)



This repo is also a place for exploration in the land of

[bootstrapping](doc/bootstrap.md) and computing system

development. My primary drive with Maru is to clearly

and formally express that which is mostly treated as black magic:

the bootstrapping of a language on top of other languages (which

includes the previous developmental stage of the same language).



## Meta



This document aims to present an overview of Maru. There are various

documents in the [`doc/`](doc/) directory that discuss some topics in

more detail.



## How



Maru's architecture is described in [doc/how.md](doc/how.md).



#### Build instructions



To test a bootstrap cycle using one or all of the backends:



```

make test-bootstrap-x86    # defaults to the libc platform

make PLATFORM=[libc,linux] test-bootstrap[-llvm,-x86]

```



Platform specific instructions



#### Nix and NixOS



My primary platform. There's a `default.nix` file in the repo, so you

can run `nix-shell` to enter into the same environment that I use when

I work on Maru.



#### Debian, and derivatives



```

sudo apt install make time rlwrap

```



You will need LLVM, and/or a C compiler (any version beyond LLVM 8 should work):



```

sudo apt install llvm clang

```



For now the x86 backend only supports 32 bit mode. To use it you will

need to have support for compiling and running 32 bit C code. On

Debian based x86_64 systems this will install all the necessary

libraries:



```

sudo apt install gcc-multilib

```



#### MacOS



Please note that recent MacOS versions don't support 32 bit

executables anymore, but Maru's LLVM backend should work fine. I don't

test it regularly, so things may not always work out of the box.



1. Make sure XCode is installed. In a Terminal:



```

xcode-select --install

```



2. [Install Homebrew](https://brew.sh/)



```

/bin/bash -c "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install.sh)"

```



3. [Install LLVM using Homebrew](https://embeddedartistry.com/blog/2017/02/24/installing-llvm-clang-on-osx/)

```

brew install llvm

echo export PATH="$(brew --prefix llvm)/bin:$PATH" >> ~/.bash_profile

source ~/.bash_profile

```



#### Other platforms



Currently Maru should work everywhere where there's a `libc`, and either the

GNU toolchain, or LLVM is available.



Patches are welcome for other platforms.



## Who



Originally written by [Ian Piumarta](https://www.piumarta.com/software/maru/),

at around 2011. Full commit history is available in the

[`piumarta`](https://github.com/attila-lendvai/maru/tree/piumarta)

branch.



The current gardener is [[email protected]](mailto:[email protected]).



## Where



Bugs and patches: [maru github page](https://github.com/attila-lendvai/maru).



Discussion: [maru-dev google group](https://groups.google.com/forum/#!forum/maru-dev).



## Why



* Programming badly needs

[better foundations](https://github.com/nagydani/seedling/blob/master/RATIONALE.md),

and Maru is part of this exploration. The foundations should get **smaller, simpler,

more self-contained, and more approachable** by people who set out to learn programming.



* I'm fascinated by bootstrapping issues.

We lose a lot of value by not capturing the history of the growth of a language, including

the formal encoding of its build instructions. They are useful both for educational purposes,

and also for practical reasons: to have a minimal seed that is very simple to

port to a new architecture, and then have a self-contained, formal bootstrap process that

can automatically "grow" an entire computing system on top of that freshly laid, tiny foundation.



* Ian seems to have abandoned Maru, and his published archive couldn't

be run as-is. But it's an interesting piece of code that deserves a

repo and a maintainer to keep bitrot at bay.



* This work is full of puzzles that are a whole lot of fun to solve!



## Contribution



You are very welcome to contribute, but beware that until further notice

**this repo will receive forced pushes** (i.e.

**`git push -f`** rewriting git history (except the `piumarta` branch)). This will stop

eventually when I settle with

a build setup that nicely facilitates bootstrapping multiple, parallel paths of

language development. Please make sure that you open a branch for your work,

and/or that you are ready for some `git fetch` and `git rebase`.



## Status



### Maru's status



Backporting and bootstrapping the latest semantics from the `piumarta`

branch is done: the `eval.l` in the latest branch of this repo should

be semantically equivalent with the `eval.l` that resides in the

`piumarta` branch, although, we have arrived to this state on two

different paths:



  - Ian, while evolving Maru, kept his `eval.c` and `eval.l`

    semantically in sync



  - in contrast, I have bootstrapped the new features: I started out

    from a minimal version of the `eval.l` + `eval.c` couple (the

    [original version](https://www.piumarta.com/software/maru/)

    published on Ian's website). Then I bootstrapped the features of

    the later stages of `eval.l` using an earlier stage of itself. I

    only use the 2300 LoC of throwaway C code as the initial stepping

    stone in the bootstrap process, but once the first step is made

    the C code is left behind.



There is one major bug left that I failed to fix while I was actively

hacking on Maru. It's discussed in

https://github.com/attila-lendvai/maru/issues/8.



### Notable new features



There are several Maru stages/branches now, introducing non-trivial

new features. Some that are worth mentioning:



  - Introduction of [*platforms*](platforms.md), and notably the

    `linux` platform that compiles to a statically linked executable

    that only uses Linux kernel

    [`syscalls`](https://en.wikibooks.org/wiki/X86_Assembly/Interfacing_with_Linux);

    From a practical perspective this is almost equivalent with

    running directly on the bare metal (i.e. all dynamically allocated

    memory needs to be managed by our own GC, all IO behind our own

    abstractions, etc).



  - The host and the slave are isolated while bootstrapping which makes it possible to

    do things like reordering types (changing their type id in the target),

    or changing their object layout.



  - Relying on this isolation, the code in `eval.l` now looks pretty much the same

    as something that is meant to be loaded into the evaluator (i.e. the function

    implementing `car` in `eval.l` is now called `car`). This paves the way for

    metacircularity: to be able to "bring alive" the evaluator by loading it

    verbatim into another instance of itself (as opposed to compiling it to

    machine code and giving it to a CPU to bring it alive).



  - The addition of an LLVM backend.



### Future plans



Assorted TODO list



  - Make Maru Scheme compatible, either by forking it, or by some sort

    of a compatibility layer that is loadable into vanilla Maru. Then

    consider how that relates to [GNU Mes](https://www.gnu.org/software/mes/).



  - Finish the proof of concept in `tests/test-elf.l` to compile the

    Linux plaform directly into an ELF binary. This would reduce the

    list of external dependencies to a single one (GNU Make).



  - Rewrite the build process in Maru; eliminate dependency on GNU Make.



  - Replace the hand-written parser in `eval.l` with something

    generated by a parser generator, maybe the

    [PEG](https://en.wikipedia.org/wiki/Parsing_expression_grammar)

    compiler. More generally, make the parser extendable.



  - Implement modules and phase separation along with what is outlined in

    [Submodules in Racket - You Want it When, Again?](https://www.cs.utah.edu/plt/publications/gpce13-f-color.pdf).

    Part of this is already done and is used in the bootstrap process.



  - Compile to, and bootstrap on the bare metal of some interesting

    targets. It's already demonstrated by the Linux platform. Another

    one could be

    [pc-bios](https://github.com/cirosantilli/x86-bare-metal-examples),

    or [EFI](https://kuroko-lang.github.io/),

    because it's easily testable using QEMU. Or port it to an ARM

    board (like Raspberry Pi)? Or maybe even attempt a C64 port?



  - Revive all the goodies in the `piumarta` branch, but in a structured way.



  - Investigate [Cranelift](https://github.com/bytecodealliance/wasmtime/tree/main/cranelift)

    and consider adding it as a backend.



  - Simplify the types-are-objects part and its bootstrap, and maybe even

    make it optional?



  - Weed out some of the added bloat/complexity (e.g. compile closures

    instead of ``s, and use them to implement streams; write a

    tree shaker; etc).



  - Merge the language and API that the compiler and the evaluator understands;

    i.e. make the level-shifted code (`eval.l` & co.) less different than code

    understood by the evaluator. This would mean that we can e.g. load/compile

    `source/buffer.l` both into the level-shifted code and into the evaluator.

    This is slowly happening, but it's nowhere near done, and I'm not even sure

    what being done means here.



  - Use LLVM's [tablegen](https://llvm.org/docs/TableGen/index.html)

    definitions to generate machine code assemblers for various CPU

    architectures. It requires either the reimplementation of the

    tablegen parser/logic in Maru (doesn't seem to be trivial), or

    writing C++ code (uhh!) to compile the data to something that is

    easy to work with in Maru.



  - Maybe add [PEG-based tree rewriter](https://www.piumarta.com/S3-2010/)

    to the repo as a branch, and use it as a bootstrap stage. It seems to

    be an earlier, or different iteration of the same idea.



  - Introduce a simplified language that drops some langauge features,

    e.g. remove *forms* and the *expand* protocol. Make sure that this

    language can bootstrap itself off of C99. Then reintroduce *forms*

    and *expand* by using this simplified Maru as the bootstrap host.



  - Understand and incorporate François René Rideau's model of

    [First Class Implementations: Climbing up the Semantic Tower](https://www.youtube.com/watch?v=fH51qhI3hq0),

    (see this [couple of page summary](https://github.com/fare/climbing), or

    see his [page on reflection](http://fare.tunes.org/reflection.html))



### History and perspective



#### Around 2010-2013

Maru was developed as part of Alan Kay's *Fundamentals of New Computing* project,

by the *[Viewpoints Research Institute](https://web.archive.org/web/20111002111856/http://www.viewpointsresearch.org/fonc_wiki/index.php/Idst)*.

The goal of the project was to implement an entirely new, self-hosting computing system, with GUI, in 20.000 lines of code.



At some point VPRI went quiet and closed down in 2018. Much of their online content disappeared, and the team (probably) also dissolved.



Their annual reports:

[2007](http://www.vpri.org/pdf/tr2007008_steps.pdf),

[2008](http://www.vpri.org/pdf/tr2008004_steps08.pdf),

[2009](http://www.vpri.org/pdf/tr2009016_steps09.pdf),

[2010](http://www.vpri.org/pdf/tr2010004_steps10.pdf),

[2011](http://www.vpri.org/pdf/tr2011004_steps11.pdf),

[2012](http://www.vpri.org/pdf/tr2012001_steps.pdf).



#### This git repo



The `piumarta` branch of this git repo is a conversion of Ian Piumarta's Mercurial

repo that was once available at

[http://piumarta.com/hg/maru/](http://piumarta.com/hg/maru/).

To the best of my knowledge

this is the latest publicly available state of Ian's work. This repo was full of

assorted code, probably driving the VPRI demos.



The `piumarta` branch will be left stale (modulo small fixes and cleanups).

My plan is to eventually revive most of the goodies from this branch, but in a

more organized and approachable manner, and also paying attention to the

bootstrapping issues.



Ian published another Mercurial repo somewhere halfway in the commit history

with only a couple of commits from around 2011. I assume that it was meant to hold

the [minimal/historical version](https://www.piumarta.com/software/maru/)

of Maru that can already self-host. I started out

my work from this minimal repo (hence the divergence between the `piumarta` and

the `maru.x` branches in this repo).



#### Other instances



There are some other copies/versions of Maru. Here are the ones

that I know about and contain interesting code:



- [github.com/melvinzhang/maru](https://github.com/melvinzhang/maru)



- [below-the-top](https://github.com/jbulow/below-the-top) is some kind of

  generic sexp tokenizer and evaluator written in Common Lisp that can be

  configured so that it can bootstrap Maru. I haven't tried it myself.



#### Related projects



A list of projects that are relevant in this context:



  - [sectorlisp](https://justine.lol/sectorlisp2/)

    ([github](https://github.com/jart/sectorlisp)): LISP with GC in

    436 bytes. It doesn't have a compiler, i.e. it cannot

    self-host. It only has a C implementation, an x86 assembly

    impementation (in the form of a boot sector), and John McCarthy's

    Lisp in Lisp evaluator. It would be an interesting project to add

    a compiler to it and see how the end result compares to Maru. Or

    to start growing a language as demonstrated in this repo, but

    starting out from sectorlisp. Note that sectorlisp is not

    equivalent to the first stage of Maru (the `maru.1` git branches),

    because that can already self-host, i.e. it can bootstrap itself

    off of the C implementation.



  - [Seedling](https://github.com/nagydani/seedling/): a ladder of

    languages, with a minimalistic core language at the bottom called

    *Seed* (it's a Forth like). Seed can self-host in less than 1k

    LoC. The higher level languages above Seed are (going to be)

    extensions of it, and are implemented on top of Seed. Porting to a

    new architecture will be trivial. And an interesting tidbit: the

    initial bootstrap was done not by using another programming

    language/compiler, but by pen and paper!



  - [bootstrappable.org](http://bootstrappable.org/): a community

    around bootstrapping, and making/keeping projects

    bootstrapable. It brings together many interesting projects:

    [stage0](https://github.com/oriansj/stage0) (~500 byte self-hosting hex assembler),

    [live-bootstrap](https://github.com/fosslinux/live-bootstrap/),

    [GNU Mes](https://www.gnu.org/software/mes/) (Scheme + C, mutually self-hosting each other),

    [m2-planet](https://github.com/oriansj/m2-planet) (a tiny C compiler).



  - [Kalyn](https://intuitiveexplanations.com/tech/kalyn): a subset of

    Haskell semantics (mostly; not lazy), but with Lisp

    syntax. Entirely (!)  self-hosting over x86-64 in 4-5 kLoC. The

    project feels of high standard, including its documentation.



  - [nanohs](https://github.com/bkomuves/nanohs): a tiny self-hosting

    subset of Haskell.



  - [PEG-based tree rewriter](https://www.piumarta.com/S3-2010/):

    runnable code to accompany Ian Piumarta's paper called *PEG-based

    tree rewriter provides front-, middle- and back-end stages in a

    simple compiler*. Ian wrote this before Maru, and there are

    several similarities between the two. See the [mailing list

    thread](https://groups.google.com/g/maru-dev/c/0Cnq1RB-Ahk).



  - [blynn's Haskell compiler](https://github.com/blynn/compiler):

    bootstrap a Haskell compiler incrementally from C, with extensive

    documentation..



  - [RefPerSys](http://refpersys.org/): a mostly symbolic artificial

    intelligence long-term project, with ambitious Artificial General

    Intelligence goals. It contains interesting and relevant ideas, e.g. in

    [refpersys-design.pdf](http://starynkevitch.net/Basile/refpersys-design.pdf).



  - [Project Oberon](http://www.projectoberon.com/): a project which encompasses CPU,

    language, operating system and user interface, and which can be run on a relatively

    inexpensive FPGA board, and simple enough for one person to understand it all.



  - [tort](https://github.com/kstephens/tort): Inspired by Ian

    Piumarta's idst, maru and other small runtimes. Core is

    approx. 5000 lines of C.



  - [kernel](http://web.cs.wpi.edu/~jshutt/kernel.html): "Kernel is a

    conservative, Scheme-like dialect of Lisp in which **everything**

    is a first-class object." (including special forms) You may want

    to also see

    [this blog](https://axisofeval.blogspot.com/search/label/kernel).



  - [Compiling a Lisp: Overture](https://bernsteinbear.com/blog/compiling-a-lisp-0/):

    Educational article series about constructing a simple Lisp compiler,

    implemented in C.