[Haskell-cafe] A new cabal odissey: cabal-1.8 breaking its own neck by updating its dependencies

Daniel Fischer daniel.is.fischer at web.de
Sat Sep 11 15:43:10 EDT 2010

On Saturday 11 September 2010 20:38:21, Paolo Giarrusso wrote:
> Hi,
> after Andrew Coppin's odissey [1], I also had a few problem with
> cabal, which stopped installing new packages. Details will follow;
> meanwhile, here are some questions prompted by what happened:
> - when recompiling a package with ABI changes, does cabal always
> update dependent packages? It seems "not always"

cabal will not automatically update packages which depend on an updated 
package. Since it doesn't keep a record of packages depending on foo, it 
would have to check all installed packages on every update to do that.

> - it didn't update
> itself, nor refuse the breaking upgrade, and the ABI breakage caused
> linker errors on Setup.hs. Luckily, cabal was already linked so I
> could always use it for queries.
> - can cabal extract and check dependencies as specified in the .hi
> files?


> I had a broken dependency which I could see with "grep" but not
> otherwise.

ghc-pkg check?

> - is there a "specification" of which are the "core" packages?

"core" as in *do not update*?
Basically, what comes with GHC shouldn't be updated.
Though I heard updating Cabal was okay.

> Not sure if this is more useful as a bug report or as discussion, or
> if I just misused cabal and it's the only perfect software in the
> world; still I wanted to share my experience.

It's not perfect, and its guards against users breaking their package dbs 
aren't strong enough yet.
But I wouldn't want to go back to a Haskell without it.

> Also I am not sure if this is the best place - but I'm not subscribed
> to other lists, and the previous "cabal odissey" was posted here, so I
> hope it's fine.

Sure, it's about Haskell, so it's on topic here.

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