On Fri, Aug 8, 2014 at 8:00 AM, Edward Z. Yang <ezyang@mit.edu> wrote:

Hey all,

SPJ pointed out to me today that if you try to run:

cabal install --with-ghc=/path/to/inplace/bin/ghc-stage2

with the latest GHC HEAD, this probably will not actually work, because
your system installed version of Cabal is probably too old to deal with
the new package key stuff in HEAD. So, how do you get a version
of cabal-install (and Cabal) which is new enough to do what you need
it to?

The trick is to compile Cabal using your /old/ GHC. Step-by-step, this
involves cd'ing into libraries/Cabal/Cabal and running `cabal install`
(or install it in a sandbox, if you like) and then cd'ing to
libraries/Cabal/cabal-install and cabal install'ing that.

Hi all,

The new cabal-install I built last month following the instructions above started failing with recent GHC HEAD with messages like

ghc: ghc no longer supports single-file style package databases (dist/package.conf.inplace) use 'ghc-pkg init' to create the database with the correct format.

I found that repeating these steps with the latest libraries/Cabal submodule gave me a cabal-install that, so far, appears to be working with GHC HEAD. So if your cabal-install has stopped working with HEAD, try building the latest version as outlined in Edward's email.

Cabal wizards, any gotchas with current Cabal & GHC HEAD I should be aware of?

Regards,

Reid Barton