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

Open Dylan is a compiler for the Dylan programming language. It 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.

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 ~/Open-Dylan/bin/hello-world

dylan-compiler -build hello-world

Compilation of the compiler itself

  • clone this git repository.

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
  • Get XML::Parser
./configure \
   --with-mps=/path/to/mps-kit \  # if using the HARP back-end
   --with-gc=/path/to/gc \ # if using the C back-end
sudo make install

The first generation will be in Bootstrap.2/bin/dylan-compiler , and a second generation will be in /opt/opendylan-current/bin/dylan-compiler

Compilation on Windows

  • Get MPS

  • 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.

Go to the 'code' subdirectory in the MPS sources and build the mmdw target:


nmake /k /f w3i3mv.nmk mmdw.lib


make -f lii4gc.gmk mmdw.a mpsplan.a

The actual makefile you use may differ depending on your platform.
See the readme.txt file in the MPS distribution for a list.

glibc >=2.3 and linux kernel >= 2.6 required

For MPS 1.106.2 I (cgay) encountered this problem on Ubuntu 7.10: The solution
was to replace

   #define _POSIX_C_SOURCE 1


  #define _XOPEN_SOURCE 500

in both prmcli.h and pthrdext.c.  The comments in the above URL
weren't explicit about that.

For MPS 1.108.0 I (cgay) encountered this problem on Ubuntu 11.04:

  cc1: warnings being treated as errors
  protlii3.c: In function ‘sigHandle’:
  protlii3.c:115:3: error: case label is not an integer constant expression
  protlii3.c:116:3: error: case label is not an integer constant expression
  make[2]: *** [lii4gc/hi/protlii3.o] Error 1
  make[1]: *** [target] Error 2
  make: *** [mmdw.a] Error 2

To work around it edit gc.gmk to remove -Werror from CFLAGSCOMPILER.

The main point to notice here is that you don't just build the default target, as described in the MPS documentation. You must build mmdw.lib or mmdw.a instead.

The above instructions use the ci, "cool internal" variant of the MPS on Windows. On Linux, MPS_VARIANT=hi is specified in opendylan/sources/lib/run-time/pentium-linux/ The ci variant does quite a lot of sanity checks all over, which heavily impacts performance, up to a factor of three in total application runtime. If you're looking for performance figures, use the hi, "hot internal", or even wi, "white-hot internal" releases.