[GHC] #4012: Compilation results are not deterministic (was: Different stage2 results depending on the version of the bootstrapping compiler)

[GHC]

#4012: Compilation results are not deterministic
-----------------------------------+----------------------------------------
  Reporter:  kili                  |          Owner:                  
      Type:  bug                   |         Status:  new             
  Priority:  normal                |      Milestone:                  
 Component:  Compiler              |        Version:  6.12.2          
Resolution:                        |       Keywords:                  
Difficulty:  Difficult (2-5 days)  |             Os:  Unknown/Multiple
  Testcase:                        |   Architecture:  Unknown/Multiple
   Failure:  Other                 |          Patch:  0               
-----------------------------------+----------------------------------------
Changes (by simonmar):

  * status:  closed => new
  * os:  OpenBSD => Unknown/Multiple
  * component:  Build System => Compiler
  * difficulty:  => Difficult (2-5 days)
  * resolution:  invalid =>


Comment:

 Replying to [comment:4 kili]:

 > But this means if two people build packages, where one used a different
 bootstrapper for ghc than the other, they can't use each other's packages.
 I'd consider that a bug.

 The bootstrapping GHC is a red herring, as I mentioned - the fact is that
 compilation results aren't deterministic.  They never have been, in fact.

 Even if compilation results were deterministic, under what circumstances
 would you want to have two systems "use each others packages", when
 they're both using a GHC independently built from source?  If they
 independently build GHC from source, why wouldn't they build packages from
 source too?

 Note that packages are registered with an MD5 hash of the interface, so
 the package system will spot if you try to register an incompatible
 package.

 Anyway, I do agree that having deterministic compilation results is a
 desirable thing, so on second thoughts I've re-opened the bug and retitled
 it.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4012#comment:5>
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