[GHC] #4012: Compilation results are not deterministic

[GHC]

#4012: Compilation results are not deterministic
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        Reporter:  kili           |            Owner:
            Type:  bug            |           Status:  new
        Priority:  high           |        Milestone:  7.6.2
       Component:  Compiler       |          Version:  6.12.2
      Resolution:                 |         Keywords:
Operating System:                 |     Architecture:  Unknown/Multiple
  Unknown/Multiple                |       Difficulty:  Difficult (2-5 days)
 Type of failure:  Other          |       Blocked By:
       Test Case:                 |  Related Tickets:
        Blocking:                 |
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Comment (by nomeata):

 Debian is (slowly, as usual) working towards reproducible builds, and
 while some Haskell packages satisfy that requirement, others do not – see
 this message: https://lists.debian.org/debian-
 haskell/2014/02/msg00011.html

 What I find interesting is that `--show-iface` shows now change at all,
 besides a different interface hash. It would make debugging these issues
 easier if everything that takes part in the hash calculation was visible
 in `--show-iface`.

 Off your head, any idea what else could contribute to a interface change?

 Built paths and time stamps contribute ''not'' towards the hash, right?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:44>
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