Today I have unmasked ghc-7.6.1 in gentoo‘s haskell overlay. Quite a few of things is broken (like unbumped yet gtk2hs), but major things (like darcs) seem to work fine. Feel free to drop a line on #gentoo-haskell to get the thing fixed.

Some notes and events in the overlay:

  • ghc-7.6.1 is available for all major arches we try to support
  • a few ebuilds of overlay were converted to EAPI=5 to use subslot depends (see below)
  • we’ve got working ghc-9999 ebuild with shared libraries by default! (see below)


That beast brought two major problems to it’s users:

  1. Prelude.catch gone away and is called ‘System.IO.Error.catchIOError’ now
  2. directory package broke interface to existing function ‘getModificationTime’ without old compatible variant.

While the first breakage is easy to fix by something like:

#if MIN_VERSION_base(4,6,0)
catch :: IO a -> (IOError -> IO a) -> IO a
catch = System.IO.Error.catchIOError

(or just switch to extensible-exceptions package if you need support for really old ghc versions).

The second one is literally a disaster

-getModificationTime :: FilePath -> IO ClockTime
+getModificationTime :: FilePath -> IO UTCTime

It is not as straightforward and "fixes" in various packages break PVP in a very funny way.

Look at this example.

Now that package has random signature type depending on which directory version it decided to build against.

TODO: find a nice and simple ‘:: ClockTime -> IO UTCTime’ compatibility function to end that keep creeping mess. (I wish the directory package to provide that).

Okay. Enough ranting.


Some of experienced gentoo haskell users already know about the magic haskell-updater tool written by Ivan to fix the mess after ghc upgrade or some base library upgrade.

Typical symptom of broken libraries is the similar ghc-pkg check result:

There are problems in package data-accessor-monads-fd-
  dependency "monads-fd-" doesn't exist
There are problems in package LibZip-0.10.2:
  dependency "mtl-" doesn't exist
There are problems in package jail-
  dependency "monads-fd-" doesn't exist

Why it happens?

Well, ghc’s library ABI depends on ABIs on all the libraries it uses. It has quite nasty consequences.

Once you upgrade a library you need to:

  1. rebuld all the reverse dependencies
  2. and their reverse dependencies (recursive)

The first point can be solved by EAPI 5 so called SUBSLOT feature.

The second one is not solved yet, but i was said is planned for EAPI=6. Thus you will still need to use haskell-updater time to time.

Anyway, I’ve bumped binary package today and to show how portage picks all it’s immediate users:

# emerge -av1 dev-haskell/binary

These are the packages that would be merged, in order:

Calculating dependencies... done!
[ebuild  r  U ~] dev-haskell/binary- [] USE="doc hscolour {test} -hoogle -profile" 0 kB
[ebuild  r  U ~] dev-haskell/sha-1.6.1:0/1.6.1::gentoo-haskell [1.6.0:0/1.6.0::gentoo-haskell] USE="doc hscolour -hoogle -profile" 2,651 kB
[ebuild  r  U ~] dev-haskell/zip-archive- [] USE="doc hscolour {test} -hoogle -profile" 0 kB
[ebuild  rR   ~] dev-haskell/data-binary-ieee754-0.4.3:0/0.4.3::gentoo-haskell  USE="doc hscolour -hoogle -profile" 0 kB
[ebuild  rR   ~] dev-haskell/dyre-0.8.11:0/0.8.11::gentoo-haskell  USE="doc hscolour -hoogle -profile" 0 kB
[ebuild  rR   ~] dev-haskell/hxt-  USE="doc hscolour -hoogle -profile" 0 kB
[ebuild  rR   ~] dev-haskell/hashed-storage-0.5.10:0/0.5.10::gentoo-haskell  USE="doc hscolour {test} -hoogle -profile" 0 kB
[ebuild  rR   ~] dev-haskell/dbus-core-0.9.3-r1:0/0.9.3::gentoo-haskell  USE="doc hscolour -hoogle -profile" 0 kB
[ebuild  rR   ~] dev-haskell/hoogle-4.2.14:0/4.2.14::gentoo-haskell  USE="doc fetchdb hscolour -fetchdb-ghc -hoogle -localdb -profile" 0 kB
[ebuild  rR   ~] www-apps/gitit-  USE="doc hscolour plugins -hoogle -profile" 0 kB
[ebuild  r  U ~] dev-haskell/yesod-auth- [] USE="doc hscolour -hoogle -profile" 17 kB
[ebuild  rR   ~] dev-haskell/yesod-1.1.4:0/1.1.4::gentoo-haskell  USE="doc hscolour -hoogle -profile" 0 kB

Total: 12 packages (4 upgrades, 8 reinstalls), Size of downloads: 2,668 kB

Would you like to merge these packages? [Yes/No]

I would like to rebuild all the sha (and so on) revdeps as well, but EAPI can’t express that kind of depends yet.

The EAPI=5 ebuild slowly drift to main portage tree as well.


The most iteresting thing!

With great Mark’s help we now have live ghc ebuild right out of gti tree!

One of the most notable things is the dynamic linking by default.

# ldd `which happy` # ghc-7.7.20121116 (0x00007fffb0bff000) => /usr/lib64/ghc-7.7.20121116/containers- (0x00007fe616972000) => /usr/lib64/ghc-7.7.20121116/array- (0x00007fe6166d0000) => /usr/lib64/ghc-7.7.20121116/base- (0x00007fe615df9000) => /usr/lib64/ghc-7.7.20121116/integer-gmp- (0x00007fe615be6000) => /usr/lib64/ghc-7.7.20121116/ghc-prim- (0x00007fe615976000) => /usr/lib64/ghc-7.7.20121116/rts-1.0/ (0x00007fe615715000) => /lib64/ (0x00007fe61536c000) => /usr/lib64/ghc-7.7.20121116/containers- (0x00007fe615162000) => /usr/lib64/ (0x00007fe614ef4000) => /usr/lib64/ (0x00007fe614cec000) => /lib64/ (0x00007fe6149f2000) => /lib64/ (0x00007fe6147ea000) => /lib64/ (0x00007fe6145e6000)
    /lib64/ (0x00007fe616d41000) => /lib64/ (0x00007fe6143ca000)

$ ls -lh `which pandoc` # ghc-7.7.20121116
-rwxr-xr-x 1 root root 6.3M Nov 16 16:38 /usr/bin/pandoc
$ ls -lh `which pandoc` # ghc-7.4.2
-rwxr-xr-x 1 root root 27M Nov 18 17:46 /usr/bin/pandoc

Actually, the whole ghc-9999 installation is 150MB smaller, than ghc-7.4.1 on amd64.

Quite a win!

And as a side effect revdep-rebuild (or portage’s FEATURES=preserved-rebuild) can note (and fix) introduced breakages due to upgrades!

Work on the ghc cross-compilation in the ebuild slowly continues (needs some upstream fixes to support toolchains inferred from build/host/target triplets).

Have fun!

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