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 1.114 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 commands will build and run 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.

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 --prefix=/opt/opendylan-current
sudo make install

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

If you are on a platform using MPS (x86-linux or x86-freebsd), you will need to 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

See the Dependencies section above for details on obtaining a copy of the MPS library.

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 the location of the Boehm GC. 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 can not 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.

Make sure that the target installation directory has been deleted. If you try to install into a directory that already has an older version of Open Dylan in it, the build will fail.

Running Tests

We have an extensive set of tests which can be run once a full bootstrap (the default build, 3-stage-bootstrap) 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.

Compilation on Windows

  • Get MPS. 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), 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.