Re: [Haskell-cafe] Re: Unable to install packages

On 10-11-28 09:55 AM, Ketil Malde wrote:

Joachim Breitner writes:

...

I would not recommend using --global on Debian/Ubuntu-systems, as it might interfere with packages installed by Debian.

But 'cabal install --global' installs in /usr/local/, does it not? And official packages (i.e. debs) put stuff in /usr, so these would be separate.

Metadata is more important than data. In the case of Debian/Ubuntu's GHC, both 'cabal install --global' and 'apt-get install' records in /var/lib/ghc-6.12.3/package.conf.d If you cabal install one version and apt-get another version, sure, they are two different records in the metadata, no immediate problem. But how about cabal install --global binary apt-get install libghc6-binary-dev They are the same version (at the time of writing, and assume Ubuntu 10.10) and they will fight for the unique throne of "binary-0.5.0.2" in the metadata. The immediate problem: they likely have different ABI hashes because they're built differently. Suppose you cabal install --global binary (suppose it becomes binary-0.5.0.2-300339c66a688207241e4643a9e17721) cabal install --global I-depend-on-binary apt-get install libghc6-binary-dev (this is binary-0.5.0.2-32d59ff8fdfc79aa888e82997612374d in Ubuntu 10.10 i386 32-bit) Now I-depend-on-binary is hosed. It was built against binary-0.5.0.2-300339c66a688207241e4643a9e17721 but that's usurped. OK, who would knowingly usurp his/her own binary-0.5.0.2? Of course no one knowingly does. But everyone does it unknowingly: cabal install --global maccatcher (this brings in binary) apt-get install libghc6-agda-dev (this brings in libghc6-binary-dev) Now maccatcher is hosed. See also my http://www.vex.net/~trebla/haskell/sicp.xhtml P.S. Deleting "--global" mitigates this problem but causes some other problem. I will describe it in my article in the future.