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(Contingency Plan)
(Change announced on 2014-04-02)
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Revision as of 14:15, 2 April 2014

GHC 7.8


Update the GHC Haskell compiler to the major new 7.8 release, and update/rebuild all Haskell packages against it.


Current status

  • Targeted release: Fedora 21
  • Last updated: 2014-04-01
  • Tracker bug: <will be assigned by the Wrangler>

Detailed Description

  • The involves updating ghc from 7.6.3 to 7.8.1 (or later), and rebuilding/updating all Fedora Haskell packages.
  • The initial work will be done locally offline to make sure that it is possible to build all our packages with ghc-7.8 and the latest updated libraries.
  • This may also include building with the llvm backend to ensure that building on ARM will work.
  • Once that is completed, building will be done into Koji for rawhide and testing done.

Benefit to Fedora

GHC 7.8 is major new version of the major Haskell compiler with many new features and enhancements. See the upstream release notes link below for more details on the changes.

For example the new runtime I/O manager scales significantly better for larger workloads compared to the previous one: it should scale linearly up to approximately 32 cores (reference).


  • Proposal owners:
    • locally test rebuilding and updating of all packages
    • update macros to subpackage static libraries
    • push changes to Koji
    • testing
  • Other developers:
    • If you own a package which contains some Haskell code built with ghc you will need to rebuild you package to make sure it still rebuilds with ghc-7.8. Feel free to contact the Haskell SIG if we need assistance with fixing any build breakage, and we will try to help out.
  • Release engineering: not required
  • Policies and guidelines:
    • There may be some lesser changes to the Haskell Packaging Guidelines needed - they could be done after this Change.

Upgrade/compatibility impact

  • Upgrading will be tested and should Just Work.
  • Local user code may need some minor changes to build with ghc-7.8.

How To Test

  1. yum install ghc cabal-install cabal-rpm pandoc xmonad git-annex hledger
  2. Check these packages install, run correctly, and can build Haskell and Hackage packages.

User Experience

User using GHC to programming or develop in Haskell will benefit from the new features and performance enhancements of the latest version of the ghc compiler. Additionally various package upgrades will also improve the experience for users of Haskell packages.


GHC 7.8.1 will be released soon. There will probably be a 7.8.2 bugfix release which would be good to target

There are a few packages outside the Haskell SIG that use ghc for some part of their build. Assistance can be provided if needed to build them with latest ghc.

Contingency Plan

  • Contingency mechanism: revert ghc to current 7.6.3 and rebuild other packages if necessary (Proposal Owners)
  • Contingency deadline: Beta Freeze
  • Blocks release: No
  • Blocks product: N/A


Release Notes