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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 reading this inside of a binary release that you just downloaded and unpacked, then this is all you need to do to get started:

$ export PATH=/path/to/opendylan-2020.1/bin:$PATH    # for bash

Verify that the downloaded version is working correctly by building a hello-world binary:

make-dylan-app hello-world
cd hello-world
dylan-compiler -build hello-world

Note: If there is no _build directory already, dylan-compiler will create it and build all used libraries. Subsequent builds will be much faster.

If this is your first time trying Open Dylan, take a look at the Getting Started guide.


The rest of this document is for those interested in working on the compiler and core libraries.

Open Dylan is written in Dylan, thus a Dylan compiler is needed to bootstrap it. Download a release from and test it as described above.

Building Open Dylan

Clone the git repository:

git clone git:// --recursive

It does not work to download a ZIP file of the repository from github because it doesn't include git submodules.



Binary releases come packaged with all of the necessary dependencies. The current binary release includes

If you build from source, you may need to supply these dependencies as described below.

All 64-bit platforms and macOS must use the Boehm Demers Weiser conservative GC (or just "Boehm GC") with the LLVM or C back-end. The Memory Pool System (MPS) is only integrated with the HARP back-end, which itself only works on 32-bit x86 platforms.

  • 64-bit systems and macOS (LLVM or C back-end) -> boehm-gc, usually installed via a package (see below).
  • 32-bit x86 Linux or FreeBSD (HARP back-end) -> MPS 1.114

On macOS, 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, Debian, etc, you can install the necessary dependencies with:

apt-get install autoconf automake clang-10 gcc libgc-dev libunwind-dev

The libunwind library is an optional dependency on Linux and FreeBSD. If available, it is used to display stack traces for unhandled error conditions. (The libunwind API is built-in on macOS.)

You may also want to install lldb-10 for debugging if you are using the LLVM back-end.


To build dylan-compiler, make-dylan-app, and several tools:

export PATH=$(dirname $(which dylan-compiler)):$PATH
./configure --prefix=/opt/opendylan-current   # (but see note below)
sudo make install

The build process attempts to select the correct garbage collector implementation based on your platform.

If you are on x86-linux or x86-freebsd you must add a flag to configure to point it at the MPS sources, using --with-mps:

./configure --prefix=/opt/opendylan-current --with-mps=/path/to/mps

/path/to/mps should point to the root directory of the MPS distribution, for example --with-mps=/opt/mps-kit-1.114.0.

On other platforms, the Boehm GC will be used. If you have installed the Boehm GC via your operating system package manager, you may not need to specify its location; it will be found automatically if it is in /usr or /usr/local. If you have installed the Boehm GC into a non-standard location or the configure script cannot find it, you can point it in the right direction by using --with-gc:

./configure --prefix=/opt/opendylan-current --with-gc=/path/to/boehm

By default, 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.

Running Tests

There is an extensive set of tests which can be run once the build is complete:

make check

This runs the tests for the core language implementation as well as for many bundled libraries. However, there are currently many test failures which need to be fixed. Most of the test failures are minor issues or are due to unimplemented tests rather than major bugs. Help is welcome in improving our test suites.


  • Get MPS 1.108. Be sure that you have the older 1.108 release and not the newer 1.114 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) and set the environment variable SDK4MEMORY_POOL_SYSTEM to <where you unpacked MPS>.

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

  • cd into build\windows and run:

    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).