Layout of important files and directories

This page summarises the overall file and directory structure of GHC. We include both source files and generated files; the latter are always identified "build-tree only".

Everything starts with the main GHC repository (see Building/GettingTheSources). The build system calls that directory $(TOP). All the paths below are relative to $(TOP).

Files in $(TOP)

Despite the name "package", this file contains the master list of the *repositories* that make up GHC. It is parsed by ./boot.
Lists the various tarballs (binary packages) that ghc relies on and where to unpack them during a build.
Run validate (a shell script) before committing (see TestingPatches). The script is documented in the file itself.
Documentation files
GNU autoconf machinery
aclocal.m4, config.guess, config.sub,, install-sh,,
The top-level Makefile: see GHC Build System Architecture. GHC requires GNU make.
Make system files, MAKEHELP, SUBMAKEHELP


The libraries/ directory contains all the packages that GHC needs to build. It has one sub-directory for each package repository (e.g. base, haskell98, random). Usually each such repository builds just one package, but there is more than one in dph.

GHC's libraries are described in more detail on the libraries page.

compiler/, docs/, ghc/

These directories contain the main GHC compiler and documentation. The compiler/ directory contains the ghc package, which is linked into an executable in the ghc/ directory.

There is documentation of the intended module dependency structure of the compiler/ directory.

  • compiler/ the Cabal file for GHC is generated from this. If you add a module to GHC's source code, you must add it in the file too, else you'll get link errors.

The following directories appear only in the build tree:

  • compiler/stage1: generated files for the stage1 build of GHC. There are a handful of files (ghc_boot_platform.h etc), and a directory compiler/stage1/build/ that contains all the .o and .hi files for the compiler.
  • compiler/stage2: similarly stage2.

You can't run a binary from here: look in the inplace/ directory below for that.


Sources for the runtime system; see Commentary/SourceTree/Rts.


Header files for the runtime system; see Commentary/SourceTree/Includes.

utils/, libffi/

The utils directory contains support utilities that GHC uses.

These utils may be built with the bootstrapping compiler, for use during the build, or with the stage1 or stage2 compiler, for installing. Some of them are built with both; we can't install the utils built with the bootstrapping compiler as they may use different versions of C libraries. The reason we use sometimes stage2 rather than stage1 is that some utils, e.g. haddock, need the GHC API package.

  • utils/ghc-cabal is a little program we use for building the libraries. It's similar to cabal-install, but without the dependencies on http etc.
  • utils/count_lines is a program that counts the number of source-code lines in GHC's code-base. It distinguishes comments from non-comments.


This contains some simple wrapper programs and scripts, for example the ghci wrapper that invokes the ghc binary with the --interactive flag. These wrappers tend to be executable programs on Windows and scripts on Unix systems.

ghc-tarballs/ (Windows only)

This contains some tarball files (binary packages) that GHC relies upon. Used for easier development / deployment on windows.

testsuite/, nofib/

The testsuite/ and nofib/ directories contain apparatus for testing GHC.

mk/, rules/

The mk/ and directories contains all the build system Makefile boilerplate; see GHC Build System Architecture. Some particular files are interesting:

  • mk/ contains Makefile settings that control your build. Details here. The file mk/ contains a starting point that you can copy to mk/ if you want.
  • mk/ this file records the fact that you are doing validation, by containing the single line Validating=YES. That in turn means the the build system gets its settings from mk/ instead of from mk/ Remove the file to stop validating.
  • mk/ just like, but applies when validating. Use this file to override the default settings for validation, which are in mk/


Miscellaneous files for building distributions.

Stuff that appears only in a build tree


The inplace/ directory is where we "install" stage1 and stage2 compilers, and other utility programs, when they are built, to be used when building other things in the build tree. The layout is exactly the same as that of an installed GHC on the host platform.

  • inplace/bin/: executables, including
    • ghc-stage1
    • ghc-stage2
    • ghc-pkg
    • hasktags
    • hsc2hs
    • haddock
    • count_lines
    • compareSizes
  • inplace/lib/: suppporting libraries for the executables.


In many directories, dist* subdirectories appear. These are where Cabal, and the build system makefiles, put all of the files generated while building. Some particularly interesting files are:

  • docs/users_guide/users_guide/index.html: the HTML for the user manual
  • libraries/lib/dist-install/doc/html/lib: contains the Haddock'd documentation for library lib
Last modified 4 years ago Last modified on Jan 5, 2016 10:42:24 AM