Go to http://www.mingw.org/download.shtml and download the following (of course, the version numbers will differ):

Run both executables (in the order given above) to install them. I put them in c:/msys

Set the following environment variables

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.

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.

MSYS seems to implement symbolic links by copying, so sharing is lost.

Win32 has a find command which is not the same as MSYS's find. You will probably discover that the Win32 find appears in your PATH before the MSYS one, because it's in the system PATH environment variable, whereas you have probably modified the user PATH variable. You can always invoke find with an absolute path, or rename it.

MSYS comes with bzip, and MSYS's tar's -j will bunzip an archive (e.g. tar xvjf foo.tar.bz2). Useful when you get a bzip'd dump.

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 thse 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 http://haskell.org/ghc/cygwin. When the Cygwin installer asks you to "Choose a Download Site", choose one of the offered mirror sites; and then type "http://haskell.org/ghc/cygwin" 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.

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

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 Section 13.1, “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!

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 cvs.haskell.org

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.

Install an executable GHC, from http://www.haskell.org/ghc. 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 http://www.haskell.org/happy. Happy is a parser generator used to compile the Haskell grammar. Under MSYS or Cygwin you can easily build it from the source distribution using

$ ./configure
$ make
$ make install

This should install it in /usr/local/bin (which maps to c:/msys/1.0/local/bin on MSYS). Make sure the installation directory is in your PATH.

Install an executable Alex. This can be done by building from the source distribution in the same way as Happy. Sources are available from http://www.haskell.org/alex.

GHC uses the mingw C compiler to generate code, so you have to install that (see Section 12.1, “Windows platforms: Cygwin, MSYS, and MinGW”). Just pick up a mingw bundle at http://www.mingw.org/. 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 fptools/ghc/compiler, you can use "make tags" to make a TAGS file for emacs. That uses the utility fptools/ghc/utils/hasktags/hasktags, so you need to make that first. The most convenient way to do this is by going make boot in fptools/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 http://hackage.haskell.org/trac/ghc/wiki/GhcDarcs.

If you used autoconf instead of autoreconf, 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

autoreconf seems to create the file configure read-only. So if you need to run autoreconf again (which I sometimes do for safety's sake), you get

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

Solution: delete configure first.

After autoreconf run ./configure in fptools/ thus:

$ ./configure --host=i386-unknown-mingw32 --with-gcc=c:/mingw/bin/gcc

This is the point at which you specify that you are building GHC-mingw (see Section 12.1.1, “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/fptools-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/fptools-stage1/ghc'
make: *** [all] Error 1

Be warned!

If you want to build GHC-cygwin (Section 12.1.2, “Cygwin and MSYS”) you'll have to do something more like:

$ ./configure --with-gcc=...the Cygwin gcc...

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 build.mk configuration file (see Section 7.3, “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.