Support tools for building GHC on Windows

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 http://www.mingw.org/download.shtml 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 http://www.cygwin.com/. 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 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.

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 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.

Getting MinGW

GHC uses the MinGW gcc C compiler to generate code; that is, the MinGW gcc is one of GHC's code generators. So build a working GHC, we need a MinGW gcc to hand. (See Windows platforms: Cygwin, MSYS, and MinGW.)

Just pick up a MinGW bundle at http://www.mingw.org/. We install it in c:/mingw.

Do not add any of the MinGW stuff to your path; the C compiler is only explicitly (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 MSYS/Cygwin binaries.

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 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.
  • Install an executable Alex, froim http://www.haskell.org/alex.
  • 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 python.org. I found I had to set the environment variable PYTHONHOME to the installation directory before it would work.
  • 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.