So you've decided to hack on GHC, congratulations! We hope you have a rewarding experience. This file will point you in the direction of information to help you get started right away.
The home for GHC hackers is our GitLab instance, located here:
https://gitlab.haskell.org/ghc/ghc
From here, you can file bugs (or look them up,) use the wiki, view the
git history, among other things. Of particular note is the building
page, which has the high level overview of the build process and how
to get the source:
https://gitlab.haskell.org/ghc/ghc/wikis/building
Make sure your system has the necessary tools to compile GHC. You can find an overview here:
https://gitlab.haskell.org/ghc/ghc/wikis/building/preparation
Next, clone the repository and all the associated libraries:
$ git clone --recursive [email protected]:ghc/ghc.git
On Windows, you need an extra repository containing some build tools. These can be downloaded for you by configure. This only needs to be done once by running:
$ ./configure --enable-tarballs-autodownload
First copy mk/build.mk.sample to mk/build.mk and ensure it has
your preferred build settings. (You probably want to at least set
BuildFlavour to quick):
$ cp mk/build.mk.sample mk/build.mk
$ ... double-check mk/build.mk ...
Now build. The convenient validate script will build the tree in a way which
is both quick to build and consistent with our testsuite,
$ ./validate --build-only
You can use the ./inplace/bin/ghc-stage2 binary to play with the
newly built compiler.
Now, hack on your copy and rebuild (with make) as necessary.
Then start by making your commits however you want. When you're done, you can submit a pull request on Github for small changes. For larger changes the patch needs to be submitted to GitLab for code review. The GHC Wiki has a good summary for the overall process.
An overview of things like using git, the release process, filing bugs and more can be located here:
https://gitlab.haskell.org/ghc/ghc/wikis/contributing
You can find our coding conventions for the compiler and RTS here:
https://gitlab.haskell.org/ghc/ghc/wikis/commentary/coding-style https://gitlab.haskell.org/ghc/ghc/wikis/commentary/rts/conventions
If you're going to contribute regularly, learning how to use the build system is important and will save you lots of time. You should read over this page carefully:
https://gitlab.haskell.org/ghc/ghc/wikis/building/using
A web based code explorer for the GHC source code with semantic analysis and type information of the GHC sources is available at:
https://haskell-code-explorer.mfix.io/
Look for GHC in Package-name. For example, here is the link to
GHC-8.6.5.
If you want to watch issues and code review activities, the following page is a good start:
https://gitlab.haskell.org/ghc/ghc/activity
GHC is a big project, so you'll surely need help. Luckily, we can provide plenty through a variety of means!
If you're an IRC user, be sure to drop by the official #ghc channel
on freenode. Many (but not all) of the
developers and committers are actively there during a variety of
hours.
In the event IRC does not work or if you'd like a bigger audience, GHC has several mailing lists for this purpose. The most important one is ghc-devs, which is where the developers actively hang out and discuss incoming changes and problems.
There is no strict standard about where you post patches - either in
ghc-devs or in the bug tracker. Ideally, please put it in the bug
tracker with test cases or relevant information in a ticket, and set
the ticket status to patch. By doing this, we'll see the patch
quickly and be able to review. This will also ensure it doesn't get
lost. But if the change is small and self contained, feel free to
attach it to your email, and send it to ghc-devs.
Furthermore, if you're a developer (or want to become one!) you're undoubtedly also interested in the other mailing lists:
- glasgow-haskell-users is where developers/users meet.
- ghc-commits for commit messages when someone pushes to the repository.
Happy Hacking! -- The GHC Team