wiki:Commentary/Libraries

Version 11 (modified by igloo, 5 years ago) (diff)

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GHC Commentary: Libraries

All GHC installations contain a set of libraries called the boot packages. They are so called because the boot packages are the ones required for GHC to compile itself (the stage-2 compiler).

The boot packages, along with the other subcomponents of the GHC build system, are in the file packages in a GHC tree. To get a list of them, you can run make show VALUE=PACKAGES in a configured GHC build tree. (This variable is set in $(TOP)/ghc.mk.)

  • At the root of the hierarchy we have ghc-prim. As the name implies, this package contains the most primitive types and functions. It only contains a handful of modules, including GHC.Prim (which contains Int#, +#, etc) and GHC.Bool, containing the Bool datatype.
  • Above ghc-prim is the integer-impl package, where impl is one of gmp and simple, which provides a definition of the Integer type (on top of the C gmp library, or in plain Haskell, respectively). Which functionality is provided in ghc-prim is mostly driven by what functionality the integer-impl packages need. By default integer-gmp is used; to use integer-simple define INTEGER_LIBRARY=integer-simple in mk/build.mk.
  • Next is the base package. This contains a large number of modules, many of which are in one big cyclic import knot, mostly due to the Exception type.
  • On top of base are a number of other, more specialised packages, whose purpose is generally clear from their name. If not, you can get more detail from the descriptions in their Cabal files. Currently these packages are are:
    • array
    • bytestring
    • Cabal
    • containers
    • directory
    • extensible-exceptions
    • filepath
    • haskeline
    • haskell98
    • hpc
    • mtl
    • old-locale
    • old-time
    • packedstring
    • pretty
    • process
    • random
    • syb
    • template-haskell
    • terminfo
    • unix
    • utf8-string
    • Win32

The haskell98, old-time and random packages are mostly only needed for Haskell 98 support, although dph currently uses random too.

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