[GHC] #7359: unix-2.6.0.0 fails to install on mac os x with 7.4.* (works with 7.6.1)

[GHC]

#7359: unix-2.6.0.0 fails to install on mac os x with 7.4.* (works with 7.6.1)
-------------------------------+--------------------------------------------
    Reporter:  AndreasVoellmy  |       Owner:  igloo  
        Type:  bug             |      Status:  new    
    Priority:  highest         |   Milestone:  7.6.3  
   Component:  libraries/unix  |     Version:  7.4.1  
    Keywords:  unix package    |          Os:  MacOS X
Architecture:  x86_64 (amd64)  |     Failure:  Other  
  Difficulty:  Unknown         |    Testcase:         
   Blockedby:                  |    Blocking:         
     Related:                  |  
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Comment(by MtnViewMark):

 Upon further investigation of George's situation, which I suspect is the
 same as others, this is version of "Cabal hell":

 George's system had multiple versions of packages, including some newer
 versions of packages that are supplied with GHC.

 A line from verbose cabal output tells the story:

 {{{
 rejecting: unix-2.5.1.1/installed-296... (conflict: cairo =>
 bytestring==0.10.0.1/installed-9b0..., unix =>
 bytestring==0.9.2.1/installed-004...)
 }}}

 That is, cabal rejected the installed unix-2.5.1.1 because it was compiled
 against bytestring-0.9.2.1 (both supplied with GHC 7.4.1, and with HP
 2012.4.0.0)... and the installed version of cairo it picked (0.12.4) was
 compiled against bytestring-0.10.0.1 (which was also installed). The only
 solution cabal could find was to pick unix-2.6.0.1. However, that, as we
 know (and expect) is incompatible with GHC-7.4.2.

 So the bug is that unix should have some dependency on ghc, which in turn
 would cause Cabal to give up in this situation - because the compiler
 essentially constrains the version of unix to just one.

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/7359#comment:11>
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