Non-deterministic behaviour when overlapping packages are installed #697

bos opened this Issue May 24, 2012 · 2 comments


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bos commented May 24, 2012

(Imported from Trac #705, reported by guest on 2010-06-25)


This user took a standard Haskell Platform install, installed a new version of the time package, and then installed random. The random package was rebuilt and installed against the new time package. However, re-running cabal install random installs random again; it doesn't reach a fixed point.

The problem (I presume) is that when cabal-install merges the package databases it chooses which random- to use non-deterministically. In fact it seems to depend on the exact package Ids, because I get different results with GHC 6.12.2 where the package Ids of the two random- packages are ordered differently.

I realise there are larger issues about how to do resolution here, but I think at least we should make cabal-install deterministic, and preferably idempotent.

bos commented May 24, 2012

(Imported comment by @kosmikus on 2010-06-25)

I should check if this is still a potential issue, also in combination with the modular solver.

tibbe commented May 5, 2014

Closing as there's been no activity in years. Please re-open (or file a new bug) if the problem reappears.

@tibbe tibbe closed this May 5, 2014
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