TruffleSOM - The Simple Object Machine Smalltalk implemented using Oracle's Truffle Framework

Introduction

SOM is a minimal Smalltalk dialect used to teach VM construction at the Hasso Plattner Institute. It was originally built at the University of Århus (Denmark) where it was used for teaching and as the foundation for Resilient Smalltalk.

In addition to TruffleSOM, other implementations exist for Java (SOM), C (CSOM), C++ (SOM++), and Squeak/Pharo Smalltalk (AweSOM).

A simple Hello World looks like:

Hello = (
  run = (
    'Hello World!' println.
  )
)

This repository contains the Truffle-based implementation of SOM, including SOM's standard library and a number of examples. Please see the main project page for links to other VM implementations.

Obtaining and Running TruffleSOM

To checkout the code, please note that we use git submodules. To obtain a proper checkout, it is easiest to use a recursive clone such as:

git clone --recursive https://github.com/SOM-st/TruffleSOM.git

Then, TruffleSOM can be build with Ant:

ant jar

Afterwards, the tests can be executed with:

./som.sh -cp Smalltalk TestSuite/TestHarness.som

A simple Hello World program is executed with:

./som.sh -cp Smalltalk Examples/Hello/Hello.som

Information on previous authors are included in the AUTHORS file. This code is distributed under the MIT License. Please see the LICENSE file for details.

TruffleSOM Implementation

TruffleSOM implements a file-based Smalltalk with most of the language features common to other Smalltalks. This includes support for objects, classes, methods, closures/blocks/lambdas, non-local returns, and typical reflective operations, e.g., method invocation or object field access.

The implementation of TruffleSOM is about 3500 lines of code in size and is a concise but comprehensive example for how to use the Truffle framework to implement standard language features.

Its parser creates a custom AST that is geared towards representing the executable semantics. Thus, we did not include AST nodes that have structural purpose only. Instead, we concentrated on the AST nodes that are relevant to express Smalltalk language semantics.

Currently TruffleSOM demonstrates for instance:

• method invocation: som.vmobjects.Method.invoke(..)
• usage of Truffle frames
• argument passing som.interpreter.nodes.Method.initializeFrame(..)
• associating AST tree nodes with source code, e.g., som.compiler.Parser.unaryMessage(..)
• support for lexical scoping and access from nested blocks, cf. ContextualNode subclasses and som.interpreter.ContextualNode.determineContext(..)
• usage of control-flow exception for
  • non-local returns, cf. som.interpreter.nodes.ReturnNonLocalNode.executeGeneric(..) as well as som.interpreter.nodes.Method.execute(..)
  • looping: som.primitives.BlockPrimitives restart as well as som.interpreter.nodes.SequenceNode.executeGeneric(..)

Build Status

Thanks to Travis CI, all commits of this repository are tested. The current build status is: