On Wed, 2008-10-15 at 09:25 +0800, Magicloud wrote:
Thank you for your reply. So the main information I got is that cabal is not safe. And my problems are all related to cabal, I think, dependency, ABI version....
You're quite right that Cabal does not track ABI versions. So it is quite possible to break dependencies of installed packages by doing things like unregistering or rebuilding a dependent package such that it gets a different ABI. There is ongoing work to make it harder to shoot yourself in the foot, by tracking the ABIs of installed packages. In the mean time all these problems can be solved by rebuilding things cleanly. It does look like there is a bug in the ghc build system where if the bootstrapping compiler has the same or higher versions of packages that the ghc build system installs then things can go wrong. We've just noticed this with ghc-6.10 but it seems likely the same bug is present in the ghc-6.8.x build system. Duncan