Version 18 (modified by simonpj, 10 years ago) (diff)


Instructions for building under Windows

This section gives detailed instructions for how to build GHC from source on your Windows machine. Similar instructions for installing and running GHC may be found in the user guide. In general, Win95/Win98 behave the same, and WinNT/Win2k behave the same.

Make sure you read the preceding section on platforms before reading section. You don't need Cygwin or MSYS to use GHC, but you do need one or the other to build GHC.

Vista users

If you're on Vista, first of all you need to disable "installer-detection", which causes strange things to happen for binaries called "setup.exe", amongst other things. Go to Start -> All Programs -> Accessories > Run and enter secpol.msc. Then under Security Settings -> Local Policies -> Security Options, disable UAC: Detect application installations and prompt for elevation. Then reboot.

When building against MingW, make sure that the paths of MingW's gcc.exe and cc1.exe are in your PATH environment variable. Best put them at the front. Otherwise Cygwin's executables might be found rather than MingW's. If you do not set the path's correctly, you may get the following error in config.log:

  configure:3321: checking for C compiler default output file name
  configure:3348: c:/MinGW/bin/gcc    conftest.c  >&5
  ld: /mingw/lib/crt2.o: No such file: No such file or directory
  configure:3351: $? = 1
  configure:3389: result:
  configure: failed program was:
  configure:3396: error: C compiler cannot create executables
  See `config.log' for more details.

From within a Cygwin terminal, you can set PATH like:

  export PATH=/cygdrive/c/MingW/bin/:/cygdrive/c/MingW/libexec/gcc/mingw32/3.4.2/:$PATH

If you are unsure whether you have set PATH correctly, try to compile a simple C program with MingW's gcc first.

Installing and configuring MSYS

MSYS is a lightweight alternative to Cygwin. You don't need MSYS to use GHC, but you do need it or Cygwin to build GHC. Here's how to install MSYS.

  • Go to and download the following (of course, the version numbers will differ):
    • The main MSYS package (binary is sufficient): MSYS-1.0.9.exe
    • The MSYS developer's toolkit (binary is sufficient): msysDTK-1.0.1.exe. This provides make, autoconf, ssh and probably more besides.
    Run both executables (in the order given above) to install them. I put them in c:/msys
  • Set the following environment variables
    • PATH: add c:/msys/1.0/bin and c:/msys/1.0/local/bin to your path. (Of course, the version number may differ.) MSYS mounts the former as both /bin and /usr/bin and the latter as /usr/local/bin. Make sure that the Windows paths (e.g. C:/WINDOWS/System32) are after the MSYS paths in your PATH variable.
    • HOME: set to your home directory (e.g. c:/userid). This is where, among other things, ssh will look for your .ssh directory.
    • SHELL: set to c:/msys/1.0/bin/sh.exe
  • Check that the CYGWIN environment variable is not set. It's a bad bug that MSYS is affected by this, but if you have CYGWIN set to "ntsec ntea", which is right for Cygwin, it causes the MSYS ssh to bogusly fail complaining that your .ssh/identity file has too-liberal permissinos.

Here are some points to bear in mind when using MSYS:

  • MSYS does some kind of special magic to binaries stored in /bin and /usr/bin, which are by default both mapped to c:/msys/1.0/bin (assuming you installed MSYS in c:/msys). Do not put any other binaries (such as GHC or Alex) in this directory or its sub-directories: they fail in mysterious ways. However, it's fine to put other binaries in /usr/local/bin, which maps to c:/msys/1.0/local/bin.

Installing and configuring Cygwin

Install Cygwin from The installation process is straightforward; we install it in c:/cygwin.

You must install enough Cygwin packages to support building GHC. If you miss out any of these, strange things will happen to you. There are two ways to do this:

  • The direct, but laborious way is to select all of the following packages in the installation dialogue: cvs, openssh, autoconf, binutils (includes ld and (I think) ar), gcc, flex, make. To see these packages, click on the "View" button in the "Select Packages" stage of Cygwin's installation dialogue, until the view says "Full". The default view, which is "Category" isn't very helpful, and the "View" button is rather unobtrousive.
  • The clever way is to point the Cygwin installer at the ghc-depends package, which is kept at When the Cygwin installer asks you to "Choose a Download Site", choose one of the offered mirror sites; and then type "" into the "User URL" box and click "Add"; now two sites are selected. (The Cygwin installer remembers this for next time.) Click "Next".
    In the "Select Packages" dialogue box that follows, click the "+" sign by "Devel", scroll down to the end of the "Devel" packages, and choose ghc-depends. The package ghc-depends will not actually install anything itself, but forces additional packages to be added by the Cygwin installer.

Now set the following user environment variables:

  • Add c:/cygwin/bin and c:/cygwin/usr/bin to your PATH
  • Set MAKE_MODE to UNIX. If you don't do this you get very weird messages when you type make, such as:
    /c: /c: No such file or directory
  • Set SHELL to c:/cygwin/bin/bash. When you invoke a shell in Emacs, this SHELL is what you get.
  • Set HOME to point to your home directory. This is where, for example, bash will look for your .bashrc file. Ditto emacs looking for .emacsrc

Here are some things to be aware of when using Cygwin:

  • Cygwin doesn't deal well with filenames that include spaces. "Program Files" and "Local files" are common gotchas.
  • Cygwin implements a symbolic link as a text file with some magical text in it. So other programs that don't use Cygwin's I/O libraries won't recognise such files as symlinks. In particular, programs compiled by GHC are meant to be runnable without having Cygwin, so they don't use the Cygwin library, so they don't recognise symlinks.
  • See the notes in Installing and configuring MSYS about find and bzip, which apply to Cygwin too.
  • Some script files used in the make system start with "#!/bin/perl", (and similarly for sh). Notice the hardwired path! So you need to ensure that your /bin directory has at least sh, perl, and cat in it. All these come in Cygwin's bin directory, which you probably have installed as c:/cygwin/bin. By default Cygwin mounts "/" as c:/cygwin, so if you just take the defaults it'll all work ok. (You can discover where your Cygwin root directory / is by typing mount.) Provided /bin points to the Cygwin bin directory, there's no need to copy anything. If not, copy these binaries from the cygwin/bin directory (after fixing the sh.exe stuff mentioned in the previous bullet).
  • By default, cygwin provides the command shell ash as sh.exe. It seems to be fine now, but in the past we saw build-system problems that turned out to be due to bugs in ash (to do with quoting and length of command lines). On the other hand bash seems to be rock solid. If this happens to you (which it shouldn't), in cygwin/bin remove the supplied sh.exe (or rename it as ash.exe), and copy bash.exe to sh.exe. You'll need to do this in Windows Explorer or the Windows cmd shell, because you can't rename a running program!

Configuring SSH

ssh comes with both Cygwin and MSYS. (Cygwin note: you need to ask for package openssh (not ssh) in the Cygwin list of packages; or use the ghc-depends package -- see Installing and configuring Cygwin.)

There are several strange things about ssh on Windows that you need to know.

  • The programs ssh-keygen1, ssh1, and cvs, seem to lock up bash entirely if they try to get user input (e.g. if they ask for a password). To solve this, start up cmd.exe and run it as follows:
    c:\tmp> set CYGWIN32=tty
    c:\tmp> c:/user/local/bin/ssh-keygen1
  • (Cygwin-only problem, I think.) ssh needs to access your directory .ssh, in your home directory. To determine your home directory ssh first looks in c:/cygwin/etc/passwd (or wherever you have Cygwin installed). If there's an entry there with your userid, it'll use that entry to determine your home directory, ignoring the setting of the environment variable $HOME. If the home directory is bogus, ssh fails horribly. The best way to see what is going on is to say
    ssh -v
    which makes ssh print out information about its activity.
    You can fix this problem, either by correcting the home-directory field in c:/cygwin/etc/passwd, or by simply deleting the entire entry for your userid. If you do that, ssh uses the $HOME environment variable instead.
  • To protect your .ssh from access by anyone else, right-click your .ssh directory, and select Properties. If you are not on the access control list, add yourself, and give yourself full permissions (the second panel). Remove everyone else from the access control list. Don't leave them there but deny them access, because 'they' may be a list that includes you!
  • In fact ssh 3.6.1 now seems to require you to have Unix permissions 600 (read/write for owner only) on the .ssh/identity file, else it bombs out. For your local C drive, it seems that chmod 600 identity works, but on Windows NT/XP, it doesn't work on a network drive (exact dteails obscure). The solution seems to be to set the $CYGWIN environment variable to "ntsec neta". The $CYGWIN environment variable is discussed in the Cygwin User's Guide, and there are more details in the Cygwin FAQ.

Other things you need to install

You have to install the following other things to build GHC, listed below.

On Windows you often install executables in directories with spaces, such as "Program Files". However, the make system doesn't deal with this situation (it'd have to do more quoting of binaries), so you are strongly advised to put binaries for all tools in places with no spaces in their path. On both MSYS and Cygwin, it's perfectly OK to install such programs in the standard Unixy places, /usr/local/bin and /usr/local/lib. But it doesn't matter, provided they are in your path.

  • Install an executable GHC, from This is what you will use to compile GHC. Add it in your PATH: the installer tells you the path element you need to add upon completion.
  • Install an executable Happy, from
  • Install an executable Alex, froim
  • If you want to run the testsuite, you'll need Python (at least version 2.4). This comes with Cygwin, but if you use MSYS you'll need to get Python separately, from I found I had to set the environment variable PHTHONHOME to the installation directory before it would work.
  • GHC uses the mingw C compiler to generate code, so you have to install that (see Windows platforms: Cygwin, MSYS, and MinGW). Just pick up a mingw bundle at We install it in c:/mingw.
    On MSYS, add c:/mingw/bin to your PATH. MSYS does not provide gcc, ld, ar, and so on, because it just uses the MinGW ones. So you need them in your path.
    On Cygwin, do not add any of the mingw binaries to your path. They are only going to get used by explicit access (via the --with-gcc flag you give to configure later). If you do add them to your path you are likely to get into a mess because their names overlap with Cygwin binaries. On the other hand, you do need ld, ar (and perhaps one or two other things) in your path. The Cygwin ones are fine, but you must have them; hence needing the Cygwin binutils package.
  • We use emacs a lot, so we install that too. When you are in $(GHC_TOP)/compiler, you can use "make tags" to make a TAGS file for emacs. That uses the utility $(GHC_TOP)/ghc/utils/hasktags/hasktags, so you need to make that first. The most convenient way to do this is by going make boot in $(GHC_TOP)/ghc. The make tags command also uses etags, which comes with emacs, so you will need to add emacs/bin to your PATH.
  • You might want to install GLUT in your MSYS/Cygwin installation, otherwise the GLUT package will not be built with GHC.
  • Finally, check out a copy of GHC sources from the darcs repository, following the instructions at

Building GHC

OK! Now go read the documentation above on building from source (Quick start: just building and installing GHC); the bullets below only tell you about Windows-specific wrinkles. Also look in the section that immediately follows this one for typical failure cases and what do to about them.

  • After sh boot run ./configure in $(GHC_TOP)/ thus:
    $ ./configure --host=i386-unknown-mingw32 --with-gcc=c:/mingw/bin/gcc --with-ld=c:/mingw/bin/ld.exe
    This is the point at which you specify that you are building GHC-mingw (see MinGW).
    Both these options are important! It's possible to get into trouble using the wrong C compiler!
    Furthermore, it's very important that you specify a full MinGW path for gcc, not a Cygwin path, because GHC (which uses this path to invoke gcc) is a MinGW program and won't understand a Cygwin path. For example, if you say --with-gcc=/mingw/bin/gcc, it'll be interpreted as /cygdrive/c/mingw/bin/gcc, and GHC will fail the first time it tries to invoke it. Worse, the failure comes with no error message whatsoever. GHC simply fails silently when first invoked, typically leaving you with this:
    make[4]: Leaving directory `/cygdrive/e/ghc-stage1/ghc/rts/gmp'
    ../../ghc/compiler/ghc-inplace -optc-mno-cygwin -optc-O 
    -optc-Wall -optc-W -optc-Wstrict-prototypes -optc-Wmissing-prototypes 
    -optc-Wmissing-declarations -optc-Winline -optc-Waggregate-return 
    -optc-Wbad-function-cast -optc-Wcast-align -optc-I../includes 
    -optc-I. -optc-Iparallel -optc-DCOMPILING_RTS 
    -optc-fomit-frame-pointer -O2 -static 
    -package-name rts -O -dcore-lint -c Adjustor.c -o Adjustor.o
    make[2]: *** [Adjustor.o] Error 1
    make[1]: *** [all] Error 1
    make[1]: Leaving directory `/cygdrive/e/ghc-stage1/ghc'
    make: *** [all] Error 1
    Be warned!
    If you want to build GHC-cygwin (MinGW) you'll have to do something more like:
    $ ./configure --with-gcc=...the Cygwin gcc... --with-ld=...the Cygwin ld.exe...
  • If you are paranoid, delete config.cache if it exists. This file occasionally remembers out-of-date configuration information, which can be really confusing.
  • You almost certainly want to set
    SplitObjs = NO
    in your configuration file (see Getting the build you want). This tells the build system not to split each library into a myriad of little object files, one for each function. Doing so reduces binary sizes for statically-linked binaries, but on Windows it dramatically increases the time taken to build the libraries in the first place.
  • Do not attempt to build the documentation. It needs all kinds of wierd Jade stuff that we haven't worked out for Win32.

What to look for if your build fails

This section collects typical failure cases, and what to do about them.

Using autoconf by mistake

If you used autoconf instead of sh boot,

you'll get an error when you run ./configure:

...lots of stuff...
creating mk/config.h
mk/config.h is unchanged
configuring in ghc
running /bin/sh ./configure  --cache-file=.././config.cache --srcdir=.
./configure: ./configure: No such file or directory
configure: error: ./configure failed for ghc

Cannot create configure

autoreconf (which gets run by sh boot) seems to create the file configure

read-only. So if you need to run sh boot again (which I sometimes do for safety's sake), you get

/usr/bin/autoconf: cannot create configure: permission denied

Solution: delete configure first.

Configure can't find darcs version

When you run your configure script, it falls over with

sh-2.04$ ./configure --with-gcc=c:/mingw/bin/gcc --with-ld=c:/mingw/bin/ld.exe --host=i386-unknown-mingw32
configure: WARNING: If you wanted to set the --build type, don't use --host.
    If a cross compiler is detected then cross compile mode will be used.
checking for GHC version date... -nThe system cannot find the file specified.
configure: error: failed to detect version date: check that darcs is in your path

This error is nothing to do with darcs! The darcs-version test in configure uses sort, and it is picking up the Windows sort (in c:\windows\system32) instead of the MSYS or Cygwin sort.

Solution: either hack the configure script by hand, or (better) make sure that MSYS/Cygwin are in your PATH before Windows. Since c:\windows\system32 is, by default, in the System Environment Variable called PATH, and System Variables come first when searching for paths, you'll have to put MSYS/Cygwin bin directory in the System PATH, before c:\windows\system32.

(Incidentally, find is another program that Windows has too, with different functionality to Unix.)

Aregument list too long

You may find this towards the end of compiling the base library:

c:\ghc\ghc-6.6.1\bin\ar.exe: creating libHSbase.a
xargs: c:/ghc/ghc-6.6.1/bin/ar: Argument list too long
make[2]: *** [libHSbase.a] Error 126
make[2]: *** Deleting file `libHSbase.a'
Failed making all in base: 1
make[1]: *** [all] Error 1
make[1]: Leaving directory `/cygdrive/c/GHC6.6.1/ghc-6.6.1/libraries'
make: *** [stage1] Error 2

Sadly the argument list has a limited length in Windows. This may be fixable somehow (Windows expertise welcomed here), but what we do is to set

SplitObjs = NO

in That stops the splitting-up of object files, and dramatically reduces the number of object files involved. Link times are also improved. (Binary size increases though.)

Also, you can arrange for the (huge) list of files to be processed iteratively, rather all at once, and that would probably be a principal solution. xargs feeds the file names to the appropriate command (e.g. ar). In $(GHC_TOP)/mk/ find the place where it is called and add this switch

xargs -n NNN

where NNN is the number of arguments processed at a time. It should be small enough to be less than the limit and large enough for the whole thing not to be too slow.

Note, that it's not good to edit in general.

A Windows build log using Cygwin

Here is a complete, from-scratch, log of all you need to build GHC using Cygwin, kindly provided by Claus Reinke. It does not discuss alternative choices, but it gives a single path that works. Please help us to keep this up to date: if you are using newer versions, let us know whether you succeed or run into issues while following this log.

- Install some editor (vim, emacs, whatever)

- Install cygwin (
    ; i used 1.5.16-1, installed in c:\cygwin
  - run 'setup.exe'
    Choose a Download Source:
	select 'download from internet';
    Select Root Install Directory:
	root dir: c:\cygwin; 
	install for: all users;
	default file type: unix
    Select Local Package Directory
	choose a spare temporary home
    Select Your Internet Connection
	Use IE5 settings
    Choose a Download Site
	Choose your preferred main mirror and
        Add ''
    Select Packages
	In addition to 'Base' (default install), 
	select 'Devel->ghc-depends'

- Install mingw (
    ; i used MinGW-3.1.0-1.exe
    ; installed in c:\mingw
  - you probably want to add GLUT 
    ; (
    ; i used glut-3.7.3-mingw32.tar

- Get recent binary snapshot of ghc-6.4.1 for mingw 
    ; (
  - unpack in c:/ghc
  - add C:\ghc\ghc-6.4.1\bin to %PATH%
    (Start->Control Panel->System->Advanced->Environment Variables)

- Get and install binary release of darcs
    ; (

- In the following, shell commands are entered in cygwin bash

- Get darcs version of ghc
    ; also, subscribe to, and possibly
    ; to, or follow the mailing list
    ; archives, in case you checkout a version with problems

  - mkdir c:/ghc-build; cd c:/ghc-build
    ; (or whereever you want your darcs tree to be)
  - darcs get --partial
  - cd ghc
  - chmod +x darcs-all
  - ./darcs-all get

- Build ghc, using cygwin and mingw, targetting mingw
  - export PATH=/cygdrive/c/ghc/ghc-6.4.1:$PATH
    ; for haddock, alex, happy (*)
  - export PATH=/cygdrive/c/mingw/bin:$PATH
    ; without, we pick up some cygwin tools at best!
  - cd c:/ghc-build
    ; (if you aren't there already)
  - sh boot
  - ./configure --host=i386-unknown-mingw32 -with-gcc=C:/Mingw/bin/gcc.exe --with-ld=C:/Mingw/bin/ld.exe
    ; we use cygwin, but build for windows
  - cp mk/ mk/
  - in mk/
    add line:       SplitObjs = NO
	(MSYS seems slow when there are zillions of object files)
    uncomment line: BuildFlavour = perf
	(or BuildFlavour = devel, if you are doing development)
    add line:       BIN_DIST=1
  - make 2>&1 | tee make.log
    ; always useful to have a log around

- Package up binary distribution
  - make binary-dist 2>&1 | tee make-bin-dist.log
    ; always useful to have a log around
  - unpack ghc-<version>-i386-unknown-mingw32.tar.bz2 somewhere in your filesystem...