Changes/GHC 7.8

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GHC 7.8

Summary

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

Owner

Current status

Detailed Description

  • This involves updating ghc from 7.6.3 to 7.8.4, and updating/rebuilding all Fedora Haskell packages. [280+ packages built]
  • 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. [done]
  • A Koji side tag will then be used to build all the packages before the Side Tag Builds Deadline. [done]
  • Once the packages have been tested, the builds will be moved into f22. [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).

Scope

  • Proposal owners:
    • locally test rebuilding and updating of all packages
    • (optional) 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: f22-ghc koji side tag [ticket]
  • 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

Fedora users 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.

Dependencies

  • GHC 7.8.3 was released 2014-07-11
  • GHC 7.8.4 bugfix released 2014-12-23

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: if it is not possible to complete the building and testing in f22-build in time for the Mass Rebuild then ghc will be reverted back to current 7.6.3 and packages rebuilt as necessary. (Proposal Owners)
  • Contingency deadline: Beta Freeze
  • Blocks release: Yes
  • Blocks product: N/A

Documentation

Release Notes