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2.3. 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:

Binary directory

known as $(bindir), holds executables that the user is expected to invoke. Notably, ghc and ghci. On Unix, this directory is typically something like /usr/local/bin. On Windows, however, this directory is always $(libdir)/bin.

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.

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.]

2.3.1. Layout of the library directory

The layout of the library directory is almost identical on Windows and Unix, as follows: layout:

    package.conf           GHC package configuration
    ghc-usage.txt          Message displayed by ghc ––help
    bin/                   [Win32 only]  User-visible binaries

    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

        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

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

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

    libHSrts.a              GHC library archives

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

Note that:

  • On Win32, the $(libdir)/bin directory contains user-visible binaries; add it to your PATH. The ghci executable is a .bat file which invokes ghc.

    The GHC executable 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. [We assume people won't invoke ghci with very long command lines.]

    On Unix, the user-invokable ghc invokes $(libdir)/ghc-version, passing a suitable -B flag.

  • $(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.