SOM++ - The Simple Object Machine implemented in C++

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 also used for teaching.

Implementations exist for instance for Java (SOM), C (CSOM), C++ (SOM++), Python & RPython (PySOM), the Truffle framework (TruffleSOM), and Squeak/Pharo Smalltalk (AweSOM).

A simple SOM Hello World looks like:

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

This repository contains the C++ implementation of SOM. The implementation of the SOM standard library and a number of examples are included as a git submodule. Please see the main project page for links to other VM implementations.

Prerequisites

The SOM standard library and examples are located in the core-lib git submodule. Before building, initialize and fetch the submodules:

git submodule update --init --recursive

Building

SOM++ uses CMake and an optimized release build can be built like this:

mkdir cmake-build && cd cmake-build
cmake -DCMAKE_BUILD_TYPE=Release ..
make -j

Afterwards, the tests can be executed with:

./SOM++ -cp ../Smalltalk ../TestSuite/TestHarness.som

A simple Hello World program is executed with:

./SOM++ -cp ../Smalltalk ../Examples/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. Additional documentation, detailing for instance the object model and how to implement primitives, is available in the doc folder.

Advanced Compilation Settings

SOM++ supports different garbage collectors, including a basic mark/sweep, and a generational GC. Furthermore, it implements different variants for integer handling.

Tagged integers:

default: off
option name: TAGGING
example: cmake .. -DUSE_TAGGING=true

Integer caching:

default: off
option name: INT_CACHE
example: cmake .. -DCACHE_INTEGER=true

Development Build and Testing

A build with assertions for development and debugging can be built with:

mkdir cmake-debug && cd cmake-debug
cmake -DCMAKE_BUILD_TYPE=Debug ..
make -j

This build also creates a unittests binary, which uses cppunit for implementation-level unit tests, to run the basic interpreter tests in TestSuite/BasicInterpreterTests, as well as the SOM test suite.

The unit tests need the SOM classpath set as follows:

./unittests -cp ../Smalltalk:../TestSuite/BasicInterpreterTests ../Examples/Hello.som

These tests can also be run with CMake, either all together with make test or using the ctest tool, which allows to run individual tests:

make test
ctest
ctest -R unittests

Code Style and Linting

To have a somewhat consistent code style and catch some basic bugs, the CI setup runs clang-format and clang-tidy as part of the CMake setup.

make check-tidy
make check-format

To run the format and fix tidy issues, we have:

make tidy
make format

Build Status

Thanks to GitHub Actions, this repository is automatically tested. The current build status is: