erikd / hadrian

Hadrian: a new build system for the Glasgow Haskell Compiler

Hadrian

Hadrian is a new build system for the Glasgow Haskell Compiler. It is based on Shake and we hope that it will eventually replace the current make-based build system. If you are curious about the rationale and initial ideas behind the project you can find more details on the wiki page and in this blog post. This project was formerly known as Shaking-up-GHC.

The new build system can work side-by-side with the existing build system. Note, there is some interaction between them: they put (some) build results in the same directories, e.g. inplace/bin/ghc-stage1.

Your first build

Beware, the build system is in the alpha development phase. Things are shaky and often break; there are numerous known issues. Not afraid? Then put on the helmet and follow these steps:

• If you have never built GHC before, start with the preparation guide.

• This build system is written in Haskell (obviously) and depends on the following Haskell packages, which need to be installed: ansi-terminal, mtl, shake, QuickCheck.

• Get the sources and run standard configuration scripts. It is important for the build system to be in the hadrian directory of the GHC source tree:

  git clone --recursive git://git.haskell.org/ghc.git
  cd ghc
  git clone git://github.com/snowleopard/hadrian
  ./boot
  ./configure # On Windows run ./configure --enable-tarballs-autodownload

• Build GHC using hadrian/build.sh or hadrian/build.bat (on Windows) instead of make. You might want to enable parallelism with -j. We will further refer to the build script simply as build. If you are interested in building in a Cabal sandbox or using Stack, have a look at build.cabal.sh and build.stack.sh scripts. Also see instructions for building GHC on Windows using Stack.

Using the build system

Once your first build is successful, simply run build to rebuild. Most build artefacts are placed into .build and inplace directories (#113).

Command line flags

In addition to standard Shake flags (try --help), the build system currently supports several others:

• --flavour=FLAVOUR: choose a build flavour. Two settings are currently supported: default and quick (adds -O0 flag to all GHC invocations and disables library profiling, which speeds up builds by 3-4x).
• --haddock: build Haddock documentation.
• --progress-info=STYLE: choose how build progress info is printed. There are four settings: none, brief (one line per build command), normal (typically a box per build command; this is the default setting), and unicorn (when normal just won't do).
• --setup[=CONFIGURE_ARGS]: setup the build system by running the configure script with CONFIGURE_ARGS arguments; also run the boot script to create the configure script if necessary. On Windows, download the required tarballs by executing mk/get-win32-tarballs.sh with appropriate parameters. You do not have to use this functionality of the new build system; feel free to run boot and configure scripts manually, as you do when using make. Beware: --setup uses network I/O which may sometimes be undesirable.
• --split-objects: generate split objects, which are switched off by default. Due to a GHC bug, you need a full clean rebuild when using this flag.

User settings

The make-based build system uses mk/build.mk to specify user build settings. We use src/Settings/User.hs for the same purpose. Feel free to experiment following the Haddock comments.

Clean and full rebuild

• build clean removes all build artefacts. Note, we are working towards a complete separation of GHC sources and build artefacts: #113.

• build -B forces Shake to rerun all rules, even if results of the previous build are still in the GHC tree.

Testing

• build validate runs GHC tests by simply executing make fast in testsuite/tests directory. This can be used instead of sh validate --fast --no-clean in the existing build system. Note: this will rebuild Stage2 GHC, ghc-pkg and hpc if they are out of date.

• build test runs GHC tests by calling the testsuite/driver/runtests.py python script with appropriate flags. The current implementation is limited and cannot replace the validate script (see #187).

• build selftest runs tests of the build system. Current test coverage is close to zero (see #197).

Current limitations

The new build system still lacks many important features:

• We only build vanilla and profiling way: #4.
• Validation is not implemented: #187.
• Only HTML Haddock documentation is supported (use --haddock flag).
• Build flavours and conventional command line flags are not implemented: #188.
• Cross-compilation is not implemented: #177.
• There is no support for installation or binary/source distribution: #219.

Check out milestones to see when we hope to resolve the above limitations.

How to contribute

The best way to contribute is to try the new build system, report the issues you found, and attempt to fix them. Please note the codebase is very unstable at present and we expect a lot of further refactoring. The documentation is currently non-existent, but we are working on it: #55, #56.

Acknowledgements

I started this project as part of my 6-month research visit to Microsoft Research Cambridge, which was funded by Newcastle University, EPSRC, and Microsoft Research. I would like to thank Simon Peyton Jones, Neil Mitchell and Simon Marlow for kick-starting the project and for their guidance. Last but not least, big thanks to the project contributors, who helped me endure and enjoy the project.