[GHC] #10090: Building ghc with "make -j12" gives different ABI hashes for base to "make -j8"

[GHC]

#10090: Building ghc with "make -j12" gives different ABI hashes for base to "make
-j8"
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              Reporter:              |             Owner:
  juhpetersen                        |            Status:  new
                  Type:  bug         |         Milestone:
              Priority:  normal      |           Version:  7.8.4
             Component:  Build       |  Operating System:  Unknown/Multiple
  System                             |   Type of failure:  None/Unknown
              Keywords:              |        Blocked By:
          Architecture:              |   Related Tickets:
  Unknown/Multiple                   |
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
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 While building ghc-7.8.4 for Fedora 22 (devel) I found that doing highly
 parallel make builds of ghc affects the ABI hash of base, etc.

 The threshold seems to be between -j8 and -j12, which likely changes the
 build order of some modules causes changes to ABI hashes.

 While it is not hard to workaround, it is not really nice so it would be
 good to track this down IMHO.  I haven't seen this kind of issue since
 7.4.2 anyway so it may be an indirect buildsystem "regression" with
 ghc-7.8?

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Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10090>
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