# Installing GHC

Installing from binary distributions is easiest, and recommended! (Why binaries? Because GHC is a Haskell compiler written in Haskell, so you've got to bootstrap it somehow. We provide machine-generated C-files-from-Haskell for this purpose, but it's really quite a pain to use them. If you must build GHC from its sources, using a binary-distributed GHC to do so is a sensible way to proceed. For the other `fptools` programs, many are written in Haskell, so binary distributions allow you to install them without having a Haskell compiler.)

This guide is in several parts:

- Installing on Unix-a-likes ().

- Installing on Windows ().

- The layout of installed files (). You don't need to know this to install GHC, but it's useful if you are changing the implementation.

## Installing on Unix-a-likes

### When a platform-specific package is available

For certain platforms, we provide GHC binaries packaged using the native package format for the platform. This is likely to be by far the best way to install GHC for your platform if one of these packages is available, since dependencies will automatically be handled and the package system normally provides a way to uninstall the package at a later date.

We generally provide the following packages:

RedHat or SuSE Linux/x86

  RPM source & binary packages for RedHat and SuSE Linux (x86 only) are available for most major releases.

Debian Linux/x86

  Debian packages for Linux (x86 only), also for most major releases.

FreeBSD/x86

  On FreeBSD/x86, GHC can be installed using either the ports tree (`cd /usr/ports/lang/ghc && make install`) or from a pre-compiled package available from your local FreeBSD mirror.

Other platform-specific packages may be available, check the GHC download page for details.

### GHC binary distributions

Binary distributions come in “bundles,” one bundle per file called `bundle-platform.tar.gz`. (See the building guide for the definition of a platform.) Suppose that you untar a binary-distribution bundle, thus:

    % cd /your/scratch/space
    % gunzip < ghc-x.xx-sun-sparc-solaris2.tar.gz | tar xvf -

Then you should find a single directory, `ghc-version`, with the following structure:

`Makefile.in`

  the raw material from which the `Makefile` will be made ().

`configure`

  the configuration script ().

`README`

  Contains this file summary.

`INSTALL`

  Contains this description of how to install the bundle.

`ANNOUNCE`

  The announcement message for the bundle.

`NEWS`

  release notes for the bundle—a longer version of `ANNOUNCE`. For GHC, the release notes are contained in the User Guide and this file isn't present.

`bin/platform`

  contains platform-specific executable files to be invoked directly by the user. These are the files that must end up in your path.

`lib/platform/`

  contains platform-specific support files for the installation. Typically there is a subdirectory for each `fptools` project, whose name is the name of the project with its version number. For example, for GHC there would be a sub-directory `ghc-x.xx`/ where `x.xx` is the version number of GHC in the bundle.

  These sub-directories have the following general structure:

  `libHSstd.a` etc:

    supporting library archives.

  `ghc-iface.prl` etc:

    support scripts.

  `import/`

    (`.hi`) for the prelude.

  `include/`

    A few C `&num;include` files.

`share/`

  contains platform-independent support files for the installation. Again, there is a sub-directory for each `fptools` project.

`html/`

  contains HTML documentation files (one sub-directory per project).

#### Installing

OK, so let's assume that you have unpacked your chosen bundles. What next? Well, you will at least need to run the `configure`
script by changing directory into the top-level directory for the bundle and typing `./configure`. That should convert `Makefile.in` to `Makefile`.

You can now either start using the tools in-situ without going through any installation process, just type `make in-place` to set the tools up for this. You'll also want to add the path which `make` will now echo to your `PATH` environment variable. This option is useful if you simply want to try out the package and/or you don't have the necessary privileges (or inclination) to properly install the tools locally. Note that if you do decide to install the package `properly' at a later date, you have to go through the installation steps that follow.

To install a package, you'll have to do the following:

1. Edit the `Makefile` and check the settings of the following variables:

   `platform`

     the platform you are going to install for.

   `bindir`

     the directory in which to install user-invokable binaries.

   `libdir`

     the directory in which to install platform-dependent support files.

   `datadir`

     the directory in which to install platform-independent support files.

   `infodir`

     the directory in which to install Emacs info files.

   `htmldir`

     the directory in which to install HTML documentation.

   `dvidir`

     the directory in which to install DVI documentation.

   The values for these variables can be set through invocation of the `configure`
   script that comes with the distribution, but doing an optical diff to see if the values match your expectations is always a Good Idea.

   Instead of running `configure`, it is perfectly OK to copy `Makefile.in` to `Makefile` and set all these variables directly yourself. But do it right!

2. Run `make install`. This should work with ordinary Unix `make`—no need for fancy stuff like GNU `make`.

3. `rehash` (t?csh or zsh users), so your shell will see the new stuff in your bin directory.

4. Once done, test your “installation” as suggested in . Be sure to use a `-v` option, so you can see exactly what pathnames it's using.

   If things don't work as expected, check the list of known pitfalls in the building guide.

When installing the user-invokable binaries, this installation procedure will install GHC as `ghc-x.xx` where `x.xx` is the version number of GHC. It will also make a link (in the binary installation directory) from `ghc` to `ghc-x.xx`. If you install multiple versions of GHC then the last one “wins”, and “`ghc`” will invoke the last one installed. You can change this manually if you want. But regardless, `ghc-x.xx` should always invoke GHC version `x.xx`.

#### What bundles there are

There are plenty of “non-basic” GHC bundles. The files for them are called `ghc-x.xx-bundle-platform.tar.gz`, where the platform is as above, and bundle is one of these:

`prof`:

  Profiling with cost-centres. You probably want this.

`par`:

  Parallel Haskell features (sits on top of PVM). You'll want this if you're into that kind of thing.

`gran`:

  The “GranSim” parallel-Haskell simulator (hmm… mainly for implementors).

`ticky`:

  “Ticky-ticky” profiling; very detailed information about “what happened when I ran this program”—really for implementors.

One likely scenario is that you will grab two binary bundles—basic, and profiling. We don't usually make the rest, although you can build them yourself from a source distribution.

The various GHC bundles are designed to be unpacked into the same directory; then installing as per the directions above will install the whole lot in one go. Note: you must at least have the basic GHC binary distribution bundle, these extra bundles won't install on their own.

#### Testing that GHC seems to be working

The way to do this is, of course, to compile and run this program (in a file `Main.hs`):

    main = putStr "Hello, world!\n"

Compile the program, using the `-v` (verbose) flag to verify that libraries, etc., are being found properly:

    % ghc -v -o hello Main.hs

Now run it:

    % ./hello
    Hello, world!

Some simple-but-profitable tests are to compile and run the notorious `nfib`
program, using different numeric types. Start with `nfib :: Int -> Int`, and then try `Integer`, `Float`, `Double`, `Rational` and perhaps the overloaded version. Code for this is distributed in `ghc/misc/examples/nfib/` in a source distribution.

For more information on how to “drive” GHC, read on...

## Installing on Windows

Getting the Glasgow Haskell Compiler (post 5.02) to run on Windows platforms is a snap: the Installshield does everything you need.

### Installing GHC on Windows

To install GHC, use the following steps:

- Download the Installshield `setup.exe` from the GHC download page haskell.org.

- Run `setup.exe`. On Windows, all of GHC's files are installed in a single directory. If you choose ``Custom'' from the list of install options, you will be given a choice about where this directory is; otherwise it will be installed in `c:/ghc/ghc-version`. The executable binary for GHC will be installed in the `bin/` sub-directory of the installation directory you choose.

  (If you have already installed the same version of GHC, Installshield will offer to "modify", or "remove" GHC. Choose "remove"; then run `setup.exe` a second time. This time it should offer to install.)

  When installation is complete, you should find GHCi and the GHC documentation are available in your Start menu under "Start/Programs/Glasgow Haskell Compiler".

- The final dialogue box from the install process reminds you where the GHC binary has been installed (usually `c:/ghc/ghc-version/bin/`. If you want to invoke GHC from a command line, add this to your PATH environment variable.

- GHC needs a directory in which to create, and later delete, temporary files. It uses the standard Windows procedure `GetTempPath()` to find a suitable directory. This procedure returns:

  - The path in environment variable TMP, if TMP is set.

  - Otherwise, the path in environment variable TEMP, if TEMP is set.

  - Otherwise, there is a per-user default which varies between versions of Windows. On NT and XP-ish versions, it might be: `c:\Documents and Settings\<username>\Local Settings\Temp`

  The main point is that if you don't do anything GHC will work fine; but if you want to control where the directory is, you can do so by setting TMP or TEMP.

- To test the fruits of your labour, try now to compile a simple Haskell program:

      bash$ cat main.hs
      module Main(main) where

      main = putStrLn "Hello, world!"
      bash$ ghc -o main main.hs
      ..
      bash$ ./main
      Hello, world!
      bash$

You do not need the Cygwin toolchain, or anything else, to install and run GHC.

An installation of GHC requires about 140M of disk space. To run GHC comfortably, your machine should have at least 64M of memory.

### Moving GHC around

At the moment, GHC installs in a fixed place (`c:/ghc/ghc-x.yy`, but once it is installed, you can freely move the entire GHC tree just by copying the `ghc-x.yy` directory. (You may need to fix up the links in "Start/Programs/Glasgow Haskell Compiler" if you do this.)

It is OK to put GHC tree in a directory whose path involves spaces. However, don't do this if you use want to use GHC with the Cygwin tools, because Cygwin can get confused when this happens. We havn't quite got to the bottom of this, but so far as we know it's not a problem with GHC itself. Nevertheless, just to keep life simple we usually put GHC in a place with a space-free path.

### Installing ghc-win32 FAQ

I'm having trouble with symlinks.

  Symlinks only work under Cygwin (), so binaries not linked to the Cygwin DLL, in particular those built for Mingwin, will not work with symlinks.

I'm getting “permission denied” messages from the `rm` or `mv`.

  This can have various causes: trying to rename a directory when an Explorer window is open on it tends to fail. Closing the window generally cures the problem, but sometimes its cause is more mysterious, and logging off and back on or rebooting may be the quickest cure.

## The layout of installed files

This section describes what files get installed where. You don't need to know it if you are simply installing GHC, but it is vital information if you are changing the implementation.

GHC is installed in two directory trees:

Library directory,

  known as `$(libdir)`, holds all the support files needed to run GHC. On Unix, this directory is usually something like `/usr/lib/ghc/ghc-5.02`.

Binary directory

  known as `$(bindir)`, holds executables that the user is expected to invoke. Notably, it contains `ghc` and `ghci`. On Unix, this directory can be anywhere, but is typically something like `/usr/local/bin`. On Windows, however, this directory must be `$(libdir)/bin`.

When GHC runs, it must know where its library directory is. It finds this out in one of two ways:

- `$(libdir)` is passed to GHC using the `-B` flag. On Unix (but not Windows), the installed `ghc` is just a one-line shell script that invokes the real GHC, passing a suitable `-B` flag. [All the user-supplied flags follow, and a later `-B` flag overrides an earlier one, so a user-supplied one wins.]

- On Windows (but not Unix), if no `-B` flag is given, GHC uses a system call to find the directory in which the running GHC executable lives, and derives `$(libdir)` from that. [Unix lacks such a system call.] That is why `$(bindir)` must be `$(libdir)/bin`.

### The binary directory

The binary directory, `$(bindir)` contains user-visible executables, notably `ghc` and `ghci`. You should add it to your `$PATH`

On Unix, the user-invokable `ghc` invokes `$(libdir)/ghc-version`, passing a suitable `-B` flag to tell `ghc-version` where `$(libdir)` is. Similarly `ghci`, except the extra flag `--interactive` is passed.

On Win32, the user-invokable `ghc` binary is the Real Thing (no intervening shell scripts or `.bat` files). Reason: we sometimes invoke GHC with very long command lines, and `cmd.exe` (which executes `.bat` files) truncates them. Similarly `ghci` is a C wrapper program that invokes `ghc --interactive` (passing on all other arguments), not a `.bat` file.

### The library directory

The layout of the library directory, `$(libdir)` is almost identical on Windows and Unix, as follows. Differences between Windows and Unix are noted thus `[Win32 only]` and are commented below.

      $(libdir)/
        package.conf           GHC package configuration
        ghc-usage.txt          Message displayed by ghc ––help

        bin/                   [Win32 only]  User-visible binaries
             ghc.exe
             ghci.exe

        unlit                  Remove literate markup

        touchy.exe             [Win32 only]
        perl.exe               [Win32 only]
        gcc.exe                [Win32 only]

        ghc-x.xx               GHC executable [Unix only]

        ghc-split              Asm code splitter
        ghc-asm	           Asm code mangler

        gcc-lib/               [Win32 only] Support files for gcc
            specs              gcc configuration

            cpp0.exe           gcc support binaries
            as.exe
            ld.exe

            crt0.o              Standard
    	   ..etc..	    binaries

            libmingw32.a        Standard
    	   ..etc..	    libraries

            *.h                 Include files

        imports/                GHC interface files
            std/*.hi              'std' library
    	lang/*.hi             'lang' library
            ..etc..

        include/                 C header files
            StgMacros.h           GHC-specific
            ..etc...              header files

            mingw/*.h            [Win32 only] Mingwin header files

        libHSrts.a              GHC library archives
        libHSstd.a
        libHSlang.a
          ..etc..

        HSstd1.o                GHC library linkables
        HSstd2.o                  (used by ghci, which does
        HSlang.o                  not grok .a files yet)

Note that:

- `$(libdir)` also contains support binaries. These are not expected to be on the user's `PATH`, but and are invoked directly by GHC. In the Makefile system, this directory is also called `$(libexecdir)`, but you are not free to change it. It must be the same as `$(libdir)`.

- We distribute `gcc` with the Win32 distribution of GHC, so that users don't need to install `gcc`, nor need to care about which version it is. All `gcc`'s support files are kept in `$(libdir)/gcc-lib/`.

- Similarly, we distribute `perl` and a `touch` replacement (`touchy.exe`) with the Win32 distribution of GHC.

- The support programs `ghc-split` and `ghc-asm` are Perl scripts. The first line says `#!/bin/perl`; on Unix, the script is indeed invoked as a shell script, which invokes Perl; on Windows, GHC invokes `$(libdir)/perl.exe` directly, which treats the `#!/bin/perl` as a comment. Reason: on Windows we want to invoke the Perl distributed with GHC, rather than assume some installed one.