Getting the GHC sources

There are two ways to get GHC sources:

1. downloading a source distribution
2. cloning Git repositories

Via source distributions

A source distribution is a file like ghc-7.8.3-src.tar.xz, which contains a complete snapshot of the source tree for a particular version of GHC. All the source distributions we provide are available from the download page.

Pros: source distributions are easy to build, because they contain the output from running certain external tools like Happy, so you don't need to install these tools.

Cons: source distributions are stuck to a particular GHC version and shouldn't be used to contribute to GHC.

Via Git repositories

GHC uses Git for revision control (version 1.7.8 or newer recommended). You must install it on your platform before executing any "git" commands.

Important: on Windows you must configure Git to check out Unix-style line endings before executing the following commands (the default behaviour is to check out Windows-style line endings) otherwise you will likely encounter issues during the build. This can be changed using the following command: git config --global core.autocrlf false (set it to "true" the same way to restore the default behavior).

The main GHC repository is located on a Gitlab instance on haskell.org and a complete GHC source tree can be obtained (located in ghc/ghc) by running the following command:

git clone --recurse-submodules https://gitlab.haskell.org/ghc/ghc.git
cd ghc # ensure you are in the ghc source tree for the following commands

Notice that we need the "--recurse-submodules" flag because GHC uses Git submodules to fetch the libraries needed to compile GHC. The "--recurse-submodules" flag ensures that submodules are cloned too (e.g. into libraries/..). If you forgot the flag, you can perform the same operation later on with the following command:

git submodule update --init --recursive

The above instructions will checkout the HEAD (or "master"), the main trunk of GHC development. There is also a branch for each stable release line, as well as branches for development of major new features. You can list the available branches with:

git branch -a

and switch between branches with:

git checkout <other-branchname>
git submodule update --init --recursive

You can update your fork of the repository with:

git fetch origin
# then checkout, rebase or merge the branch you want (out of the scope of this page)

Note: see this page for a more thorough description of some branches available in the main repository

Note: this page gives a list of all the repositories used by GHC as Git submodules.

Note: for cloning GHC 7.8 or earlier, see the legacy instructions.

Cloning from GitHub

Cloning from GitHub is also supported. The official mirror for GHC on GitHub is located at https://github.com/ghc/ghc.

First configure the following Git url rewrites to account for the different naming scheme on GitHub (due to GitHub not supporting / in repository names) before cloning (those rules are persisted in ${HOME}/.gitconfig so you need to perform it only once):

git config --global url."git://github.com/ghc/packages-".insteadOf     git://github.com/ghc/packages/ 
git config --global url."http://github.com/ghc/packages-".insteadOf    http://github.com/ghc/packages/ 
git config --global url."https://github.com/ghc/packages-".insteadOf   https://github.com/ghc/packages/ 
git config --global url."ssh://git@github.com/ghc/packages-".insteadOf ssh://git@github.com/ghc/packages/ 
git config --global url."git@github.com:ghc/packages-".insteadOf       git@github.com:ghc/packages/ 

and then simply proceed by

git clone --recurse-submodules git://github.com/ghc/ghc