Mirror of the Glasgow Haskell Compiler. Patches are best submitted to GHC's Phabricator (https://phabricator.haskell.org/), bugs and feature-requests are best filed to GHC's Trac (https://ghc.haskell.org/trac/ghc), or sent to the mailing list (ghc-devs@haskell.org). First time contributors are encouraged to get started by just sending a Pull Req…
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RyanGlScott Add a recursivity check in nonVoid
Previously `nonVoid` outright refused to call itself
recursively to avoid the risk of hitting infinite loops when
checking recurisve types. But this is too conservative—we //can//
call `nonVoid` recursively as long as we incorporate a way to detect
the presence of recursive types, and bail out if we do detect one.
Happily, such a mechanism already exists in the form of `checkRecTc`,
so let's use it.

Test Plan: make test TEST=T15584

Reviewers: simonpj, bgamari

Reviewed By: simonpj

Subscribers: rwbarton, carter

GHC Trac Issues: #15584

Differential Revision: https://phabricator.haskell.org/D5116
Latest commit e68b439 Sep 23, 2018
Failed to load latest commit information.
.arc-linters Bump arcanist-external-json-linter submodule Oct 19, 2017
.circleci use *test instead of *slowtest for llvm validation on Circle CI Aug 12, 2018
bindisttest Rework CC/CC_STAGE0 handling in `configure.ac` Apr 16, 2016
compiler Add a recursivity check in nonVoid Sep 23, 2018
distrib Bump autoconf version bound to >= 2.69 Mar 19, 2018
docs user-guide: Allow build with sphinx < 1.8 Sep 20, 2018
driver driver/utils/dynwrapper.c: Remove unused variable Feb 25, 2018
ghc Turn on MonadFail desugaring by default Aug 7, 2018
hadrian @ 4265e3a Bump hadrian submodule Aug 5, 2018
includes Fix slop zeroing for AP_STACK eager blackholes in debug build Sep 21, 2018
inplace Testsuite: suggest quoting $(TEST_HC) Oct 30, 2015
libffi-tarballs @ 96d0280 Bump libffi-tarballs submodule Oct 2, 2017
libffi No libffi docs Oct 3, 2017
libraries Revert "adds -latomic to. ghc-prim" Sep 20, 2018
mk Build debugged prof runtimes Sep 10, 2018
nofib @ a80baac Bump nofib submodule Aug 27, 2018
rts Remove redundant slop zeroing Sep 21, 2018
rules Bump Cabal submodule to 2.2 Mar 4, 2018
testsuite Add a recursivity check in nonVoid Sep 23, 2018
utils Correct submodule update for haddock Sep 15, 2018
.appveyor.sh Run tests after artifact collection Apr 7, 2018
.arcconfig arcconfig: Set project ruleset to use master merge-base by default Jul 20, 2017
.arclint Use python3 for linters Dec 23, 2016
.ghcid Add a script for running a ghci that can load and run ghc Jul 27, 2018
.gitignore Use -fobject-code in the GHCi script for loading GHC Aug 6, 2018
.gitmodules Remove dph, vector, primitive and random from .gitmodules Aug 27, 2018
.mailmap Update .mailmap [skip ci] Aug 20, 2018
.travis.yml Attempt to fix travis build Jul 12, 2018
ANNOUNCE Update ANNOUNCE Nov 22, 2017
HACKING.md Add info about Github pull requests. Oct 25, 2017
INSTALL.md Rewrite boot in Python Oct 2, 2017
LICENSE Reorganisation of the source tree Apr 7, 2006
MAKEHELP.md Rewrite boot in Python Oct 2, 2017
Makefile Revert "Move check-ppr and check-api-annotations to testsuite/utils" Nov 2, 2017
README.md Fix README Nov 23, 2017
Vagrantfile vagrant: move files around Jul 20, 2014
aclocal.m4 Revert "adds -latomic to. ghc-prim" Sep 20, 2018
appveyor.yml Full AppVeyor build with tests Mar 29, 2018
boot Make boot work if ACLOCAL_PATH is not set Jul 12, 2018
build.nix.sh Squashed 'hadrian/' changes from fa3771f..4499b29 Nov 22, 2017
config.guess Update autoconf scripts Jul 23, 2017
config.sub Update autoconf scripts from correct source May 12, 2017
configure.ac Revert "adds -latomic to. ghc-prim" Sep 20, 2018
ghc.mk Support the GHCi debugger with -fexternal-interpreter Jul 16, 2018
install-sh Update aux files `config.{guess,sub}` and `install-sh` Nov 7, 2013
llvm-passes Extract hard-coded LLVM opt flags into a file May 30, 2018
llvm-targets Add FreeBSD amd64 LLVM target Aug 9, 2018
packages Remove random submodule Jul 14, 2018
settings.in Use ar for -staticlib Sep 13, 2017
validate circleci: Detect core count Jul 6, 2018


The Glasgow Haskell Compiler

Build Status

This is the source tree for GHC, a compiler and interactive environment for the Haskell functional programming language.

For more information, visit GHC's web site.

Information for developers of GHC can be found on the GHC Trac.

Getting the Source

There are two ways to get a source tree:

  1. Download source tarballs

Download the GHC source distribution:


which contains GHC itself and the "boot" libraries.

  1. Check out the source code from git

    $ git clone --recursive git://git.haskell.org/ghc.git

Note: cloning GHC from Github requires a special setup. See Getting a GHC repository from Github.

See the GHC team's working conventions regarding how to contribute a patch to GHC. First time contributors are encouraged to get started by just sending a Pull Request.

Building & Installing

For full information on building GHC, see the GHC Building Guide. Here follows a summary - if you get into trouble, the Building Guide has all the answers.

Before building GHC you may need to install some other tools and libraries. See, Setting up your system for building GHC.

NB. In particular, you need GHC installed in order to build GHC, because the compiler is itself written in Haskell. You also need Happy, Alex, and Cabal. For instructions on how to port GHC to a new platform, see the GHC Building Guide.

For building library documentation, you'll need Haddock. To build the compiler documentation, you need Sphinx and Xelatex (only for PDF output).

Quick start: the following gives you a default build:

$ ./boot
$ ./configure
$ make         # can also say 'make -jX' for X number of jobs
$ make install

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

(NB: Do you have multiple cores? Be sure to tell that to make! This can save you hours of build time depending on your system configuration, and is almost always a win regardless of how many cores you have. As a simple rule, you should have about N+1 jobs, where N is the amount of cores you have.)

The ./boot step is only necessary if this is a tree checked out from git. For source distributions downloaded from GHC's web site, this step has already been performed.

These steps give you the default build, which includes everything optimised and built in various ways (eg. profiling libs are built). It can take a long time. To customise the build, see the file HACKING.md.

Filing bugs and feature requests

If you've encountered what you believe is a bug in GHC, or you'd like to propose a feature request, please let us know! Submit a ticket in our bug tracker and we'll be sure to look into it. Remember: Filing a bug is the best way to make sure your issue isn't lost over time, so please feel free.

If you're an active user of GHC, you may also be interested in joining the glasgow-haskell-users mailing list, where developers and GHC users discuss various topics and hang out.

Hacking & Developing GHC

Once you've filed a bug, maybe you'd like to fix it yourself? That would be great, and we'd surely love your company! If you're looking to hack on GHC, check out the guidelines in the HACKING.md file in this directory - they'll get you up to speed quickly.

Contributors & Acknowledgements

GHC in its current form wouldn't exist without the hard work of its many contributors. Over time, it has grown to include the efforts and research of many institutions, highly talented people, and groups from around the world. We'd like to thank them all, and invite you to join!