13. Instructions for building under Windows
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## 13. 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 (Section 12, “Platforms, scripts, and file names”) before reading section. You don't need Cygwin or MSYS to use GHC, but you do need one or the other to build GHC.

### 13.1. 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, cvs 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`.

  - `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`

  - `CVS_RSH`: set to `c:/msys/1.0/bin/ssh.exe`. Only necessary if you are using CVS.

  - `MAKE_MODE`: set to `UNIX`. (I'm not certain this is necessary for MSYS.)

- 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`.

- 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.

### 13.2. Installing and configuring Cygwin

Install Cygwin from http://www.cygwin.com/. The installation process is straightforward; we install it in `c:/cygwin`. During the installation dialogue, make sure that you select all of the following: cvs, openssh, autoconf, binutils (includes ld and (I think) ar), gcc, flex, make. If you miss out any of these, strange things will happen to you. 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.

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`

There are a few other things to do:

- By default, cygwin provides the command shell `ash` as `sh.exe`. We have often seen build-system problems that turn 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. So, 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!

- 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 the following binaries in it:

  - sh

  - perl

  - cat

  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).

Finally, 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 Section 13.1, “Installing and configuring MSYS” about find and bzip, which apply to Cygwin too.

### 13.3. Configuring SSH

ssh comes with Cygwin, provided you remember to ask for it when you install Cygwin. (If not, the installer lets you update easily.) Look for openssh (not ssh) in the Cygwin list of applications!

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.

### 13.4. 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 for fptools 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. 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.

- 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`.

- Finally, check out a copy of GHC sources from the CVS repository, following the instructions above (Section 2.1, “Getting access to the CVS Repository”).

### 13.5. Building GHC

OK! Now go read the documentation above on building from source (Section 7, “Building from source”); the bullets below only tell you about Windows-specific wrinkles.

- 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 7.4, “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.

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