[GHC] #16063: ghc-8.6.3 + Mac OSX + FFI dependency causes 'impossible happened' compiler failure

[GHC]

#16063: ghc-8.6.3 + Mac OSX +  FFI dependency causes 'impossible happened' compiler
failure
-------------------------------------+-------------------------------------
        Reporter:  benselfridge      |                Owner:  (none)
            Type:  bug               |               Status:  patch
        Priority:  normal            |            Milestone:
       Component:  Compiler          |              Version:  8.6.3
      Resolution:                    |             Keywords:
Operating System:  MacOS X           |         Architecture:  x86_64
 Type of failure:  Compile-time      |  (amd64)
  crash or panic                     |            Test Case:
      Blocked By:                    |             Blocking:
 Related Tickets:                    |  Differential Rev(s):  Phab:D5462
       Wiki Page:                    |
-------------------------------------+-------------------------------------
Changes (by harpocrates):

 * status:  infoneeded => patch
 * differential:   => Phab:D5462


Comment:

 Here's what I think is happening: starting in
 3d17f1f10fc00540ac052f2fd03182906aa47e35, when told to find an archive for
 `softfloat`, GHC no longer looks for just `libsoftfloat.a` and
 `softfloat.a`, it also looks for `libsoftfloat` and `softfloat`. GHC's
 method for "looking" for an archive is to make a bunch of calls to GCC.
 Something like

 {{{
 gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE
 -B/Users/atheriault/Code/grift/dist-newstyle/build/x86_64-osx/ghc-8.6.3
 /softfloat-hs-0.1.0/build --print-file-name libsoftfloat.a
 ...
 gcc -fno-stack-protector -DTABLES_NEXT_TO_CODE
 -B/Users/atheriault/Code/grift/dist-newstyle/build/x86_64-osx/ghc-8.6.3
 /softfloat-hs-0.1.0/build --print-file-name softfloat
 }}}

 We "find" a library when the path that GCC prints out is a full path
 (instead of just the path we pass in). And there's the problem: GCC will
 print out a full path to a //folder// if an appropriately named folder is
 found in the base location. In this case, GHC ends up finding the
 `Users/atheriault/Code/grift/dist-newstyle/build/x86_64-osx/ghc-8.6.3
 /softfloat-hs-0.1.0/build/SoftFloat` folder and thinking that this is the
 `softfloat` library it has been asked to find.

 One workaround is to name the `softfloat` library to `softfloat1`. Or
 rename the `SoftFloat` directory.

-- 
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/16063#comment:6>
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