Upgrading packages

A list of things that need updating when porting packages to newer library/cabal versions.

If you maintain a Haskell package this is for you. For older versions of this document:

• 2.0 migration guide (upgrading for Cabal 2.0)
• /Updating to GHC 7
• /Updating to GHC 6.10
• /Updating to GHC 6.8

Most new tips for fixing build failures are tracked at https://github.com/haskell-infra/hackage-trustees/blob/master/cookbook.md

Compatibility with older GHC

Use cabal's conditional thingy, checking on impl(ghc >= x.yz). E.g:

   ghc-options:         -Wall -fexcess-precision -funbox-strict-fields
   if impl(ghc >= 6.12)
       ghc-options:     -fno-warn-unused-do-bind