[Nix-dev] Say hello to GHC 7.7.20131202

[Peter Simons]

Hi Oliver,

 > What is the reason for making this the default for ghcHEAD?

GHC 7.7.x doesn't work well without shared library support enabled. I
tried it, but ran into all kinds of linking errors (i.e. while building
hsemail), because the code seems to expect that share-able variants of
the installed libraries are available. I guess that this behavior can be
fixed somehow, but since I wanted to try out shared library support
anyway, I just enabled it and all errors went away.

 > Will haskellPackages_ghc78whatever also have shared libraries?

Well, it already does! It's just not enabled by default. Just add the
following snippet to your ~/.nixpkgs/config.nix file

  {
    packageOverrides = pkgs:
    {
      haskellPackages = pkgs.haskellPackages_ghc763.override {
        extraPrefs = self: {
          cabal = self.cabal.override {
            enableSharedLibraries = true;
            enableSharedExecutables = true;
          };
        };
      };
    };
  }

to activate the feature.

Take care,
Peter