Kazu, thanks I wanted to mention that the "unknown symbol" error is very likely not related to the cab tool as the same error appears, when using the cabal - tool. I guess we can ignore it even in the context of my main question, sorry for being to verbose. What I found more interesting is, that cab doesn't try to re-install an installed package - already in the database too, as ghc-pkg output pretends - which is expected behaviour. The cabal system frontend obviously does trying to reinstall the package though. This seems like different model of reality... Cheers Daniel 2011/4/11 Kazu Yamamoto :

Hello,

...

When I install cabal-dev and cab first and then re-install everything with cab instead of cabal the issue with re-installing already installed packages described above disappears and only an "unknown symbol" message related to the correctly found installed cairo package remains. So is there an error in package database handling somewhere or changed semantics in cabal | ghc-pkg | (even) pkg-config flags I missed?

"cab" is just a wrapper for "cabal" and "cabal-dev" for installation. So, I have no idea about what's going on.

Please try "cab install <package> -n" to see what will happen before typing "cab install <package>". If you find the word "reinstall", you should not install the package because the installation operation will break your package environment.

You can analyze package dependency with: cab deps <package> -r cab revdeps <package> -r cab list -r

Adding the "-a" option displays global packages also.

I recommend to use a sandbox when you try to resolve a dependency problem.

--Kazu