[GHC] #12673: bkpcabal01 testcase fails with spurious output on stderr on Darwin

[GHC]

#12673: bkpcabal01 testcase fails with spurious output on stderr on Darwin
-------------------------------------+-------------------------------------
           Reporter:  bgamari        |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:  8.2.1
          Component:  Package        |           Version:  8.0.1
  system                             |
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The `bkpcabal01` testcase introduced the by Backpack merge fails on Mac OS
 X with,

 {{{
 =====> bkpcabal01(normal) 1 of 1 [0, 0, 0]
 cd "./backpack/cabal/bkpcabal01/bkpcabal01.run" && $MAKE -s --no-print-
 directory bkpcabal01 CLEANUP=1
 Actual stderr output differs from expected:
 --- /dev/null   2016-10-08 22:51:23.000000000 +0300
 +++
 ./backpack/cabal/bkpcabal01/bkpcabal01.run/bkpcabal01.run.stderr.normalised
 2016-10-08 22:51:23.000000000 +0300
 @@ -0,0 +1,4 @@
 +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib:
 file:
 dist/build/p-0.1+FBOSaiWyMx9DR2UZVI6wQJ/objs-36887/libHSp-0.1+FBOSaiWyMx9DR2UZVI6wQJ.a(H.o)
 has no symbols
 +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib:
 file:
 dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-36936/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a(I.o)
 has no symbols
 +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib:
 file:
 dist/build/p-0.1+FBOSaiWyMx9DR2UZVI6wQJ/objs-37078/libHSp-0.1+FBOSaiWyMx9DR2UZVI6wQJ.a(H.o)
 has no symbols
 +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib:
 file:
 dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-37123/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a(I.o)
 has no symbols
 *** unexpected failure for bkpcabal01(normal)
 }}}

 It seems that the problem is that `ar` produces a warning when producing
 an archive file containing an object file with no symbols,
 {{{
 bkpcabal01 bgamari$ make SETUP="./Setup -v3" bkpcabal01
 ...
 ("/usr/bin/ar",["-r","-s","-v","dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-39951/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a","dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/Q.o","dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/I.o"])
 ar: creating archive
 dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-39951/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a
 a - dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/Q.o
 a - dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/I.o
 /Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib:
 file:
 dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-39951/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a(I.o)
 has no symbols
 }}}

 In general it would be best if we could avoid linking these empty object
 files to avoid these spurious warnings.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12673>
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