[GHC] #13805: GHC 8.0.2 fails to build on macOS 10.13/Xcode 9 - preprocessor error in ghc-pkg

[GHC]

#13805: GHC 8.0.2 fails to build on macOS 10.13/Xcode 9 - preprocessor error in
ghc-pkg
-------------------------------------+-------------------------------------
        Reporter:  mistydemeo        |                Owner:  (none)
            Type:  bug               |               Status:  new
        Priority:  normal            |            Milestone:
       Component:  ghc-pkg           |              Version:  8.0.2
      Resolution:                    |             Keywords:
Operating System:  MacOS X           |         Architecture:  x86_64
 Type of failure:  Building GHC      |  (amd64)
  failed                             |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):
       Wiki Page:                    |
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Comment (by bollu):

 This was "fixed" for me by installing `gcc` and changing the settings file
 at `/usr/local/lib/ghc-8.0.2/settings` to:

 {{{
 ...
  ("Haskell CPP command","gcc"),
  ("Haskell CPP flags","-E -undef -traditional -Wno-invalid-pp-token -Wno-
 unicode -Wno-trigraphs"),
 ...
 }}}

 (I replaced `clang` with `gcc`)

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/13805#comment:3>
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