[Haskell-cafe] Things stopping pure Haskell code from having a cross-platform single semantics?

Haskell isn't like Java byte code in having a single semantics for a program irrespective of where it is run. In particular, "Int" has a platform-defined width -- so the same (pure) code can yield different answers on different machines. numCapabilities was also a "leak" of platform information, which did not require IO. But, happily, now it does not appear in the [Trustworthy] module, Control.Concurrent. Ok, what else? What other holes are there that allow my pure functions to change their answer on different machines? I'm making a list of these in a paper and I want to make sure I give a full account. Thanks, -Ryan