[GHC] #4012: Compilation results are not deterministic

[GHC]

#4012: Compilation results are not deterministic
-------------------------------------+-------------------------------------
        Reporter:  kili              |                   Owner:
            Type:  bug               |                  Status:  new
        Priority:  high              |               Milestone:  7.12.1
       Component:  Compiler          |                 Version:  6.12.2
      Resolution:                    |                Keywords:
Operating System:  Unknown/Multiple  |            Architecture:
 Type of failure:  Other             |  Unknown/Multiple
      Blocked By:                    |               Test Case:
 Related Tickets:                    |                Blocking:
                                     |  Differential Revisions:
-------------------------------------+-------------------------------------

Comment (by Fuuzetsu):

 Another sample: parallel building {{{aeson-0.8.1.0}}}, we get sections
 like

 {{{
 < 1e7b52dc510d1cf5d1c7dba94ff5093f
 <   $cr4ZN :: Constr
 < 0d767d9de53af9e99867e765de72ede2
 <   $cr4ZO :: Constr
 < dc67d4c3fc9f3ce6c26b7594d8e6eae3
 <   $cr4ZP :: Constr
 < a2def0dbb719c6f881fc717fcb8298a4
 <   $cr4ZQ :: Constr
 < c6db659c87f4f30d7cd7837ade17c21a
 <   $cr4ZR :: Constr
 < 0d876ce7c0dcbac035d3da6455b1dd5f
 <   $cr4ZS :: Constr
 ---
 > bdb4c40eb8e399497201a7ebb5b21b8e
 >   $cr5fY :: Constr
 > a1b0220e85ae58edc13e93774d8e283f
 >   $cr5fZ :: Constr
 > 7d4faa76b1cc5a7319b59dca13194f80
 >   $cr5g0 :: Constr
 > 7fdf605be2abfeb55bab02c7c6b2124d
 >   $cr5g1 :: Constr
 > 05b9af850c2c1ed35be735adcbdb7f6d
 >   $cr5g2 :: Constr
 > bb94af6dd870df350419f5d32d4917cf
 >   $cr5g3 :: Constr
 }}}

 which consequently screws up everything else. These are presumably
 generated by {{{Data}}} deriving. Attaching two sample interface files
 with the above, it was built with 7.10.1. In non-concurrent case, no
 issues.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/4012#comment:103>
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