The Open Dylan compiler and IDE.
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Welcome to Open Dylan!

Open Dylan is a compiler and a set of libraries for the Dylan programming language. If you're interested in working on the compiler and core libraries then you've come to the right place. If you want to write your own Dylan libraries and use the compiler then you should download a binary release and then read the Getting Started guide.

Open Dylan has two back-ends, HARP (which translates to native x86 code) and a C back-end.

The HARP back-end uses the Memory Pool System (MPS) from Ravenbrook, Limited to do its memory management. The MPS is available from Ravenbrook at and must be downloaded and built separately. If you are using Windows, you must download the older 1.108 release. On other platforms, the current 1.110 release is required.

The C back-end uses Boehm-Demers-Weiser conservative C/C++ garbage collector, available at

Open Dylan is written in Dylan, thus a Dylan compiler is needed to bootstrap it. Binary releases are available from

Once installed, the following command-line will produce a binary in _build/bin/hello-world in the current working directory:

dylan-compiler -build hello-world

Compilation of the compiler itself

Clone the git repository:

git clone git:// --recursive

Compilation on UNIX

Please note that on 64 bit Linux we need a big stack, the default stack is too small, please increase with ulimit -s before (safe is to double its value)


Get MPS or boehm-gc, depending on your platform:

  • Linux x86 or FreeBSD x86 (HARP) -> MPS
  • Mac OS X and all 64 bit (C) -> boehm-gc

On Mac OS X, you may find it easiest to install Homebrew and install the following:

brew install autoconf automake bdw-gc --universal

You will also need to install the command line build tools available from Apple. If your installation of bdw-gc is not universal (doesn't contain both i386 and x86_64 code), you will need to uninstall it and install again with the --universal flag.

On Ubuntu, you can install the necessary dependencies with:

apt-get install autoconf automake gcc libgc-dev


To go on and do the build:

export PATH=/path/to/opendylan/bin:$PATH
./configure \
   --with-mps=/path/to/mps-kit \  # if using the HARP back-end
   --with-gc=/path/to/boehm-gc-installation \ # if using the C back-end
make 3-stage-bootstrap
sudo make install

This will build a fully bootstrapped compiler with the first generation in Bootstrap.1/bin/dylan-compiler, the second generation in Bootstrap.2/bin/dylan-compiler, and the third in Bootstrap.3/bin/dylan-compiler. The third generation will then be installed as /opt/opendylan-current/bin/dylan-compiler.

Compilation on Windows

  • Get MPS. Be sure that you have the older 1.108 release and NOT the newer 1.110 release.

  • Make sure to have required tools installed: namely Debugging tools for Windows, a C compiler (PellesC or VC6) and Microsoft Platform SDK.

  • Open a shell (windows command processor), there set the environment variable SDK4MEMORY_POOL_SYSTEM to <where you unpacked MPS>.

  • Please keep in mind that paths with whitespaces are not well supported.

  • Go to admin\builds and do a:

    build-release.bat <target-dir> /sources <git-checkout>sources /internal

This will do a 4-stage bootstrap, in the end there will be a complete IDE in <target-dir>.

  • Building an installer:
  • Get NSIS from and the HTML help workshop (from Microsoft, to generate the chm).
  • Go to packages\win32-nsis, read Build.txt and follow the instructions. Make sure you are using the same command shell as used for building Open Dylan (to retain environment variables).

Building the MPS

This is not required anymore since it is part of building the runtime.