Hi Edward, Our new OS X build bot has noticed that the bkpcabal01 testcase introduced with your Backpack merge seems to fail on OS X with, =====> bkpcabal01(normal) 1 of 1 [0, 0, 0] cd "./backpack/cabal/bkpcabal01/bkpcabal01.run" && $MAKE -s --no-print-directory bkpcabal01 CLEANUP=1 Actual stderr output differs from expected: --- /dev/null 2016-10-08 22:51:23.000000000 +0300 +++ ./backpack/cabal/bkpcabal01/bkpcabal01.run/bkpcabal01.run.stderr.normalised 2016-10-08 22:51:23.000000000 +0300 @@ -0,0 +1,4 @@ +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: dist/build/p-0.1+FBOSaiWyMx9DR2UZVI6wQJ/objs-36887/libHSp-0.1+FBOSaiWyMx9DR2UZVI6wQJ.a(H.o) has no symbols +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-36936/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a(I.o) has no symbols +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: dist/build/p-0.1+FBOSaiWyMx9DR2UZVI6wQJ/objs-37078/libHSp-0.1+FBOSaiWyMx9DR2UZVI6wQJ.a(H.o) has no symbols +/Applications/Xcode-7.2/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/ranlib: file: dist/build/q-0.1+70e5o6lPGfgGiochTG2tqQ/objs-37123/libHSq-0.1+70e5o6lPGfgGiochTG2tqQ.a(I.o) has no symbols *** unexpected failure for bkpcabal01(normal) It seems that this message is produced by `ar` while building the .a archive, bkpcabal01 bgamari$ 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 I've opened #12673 to track this issue but until we have a chance to fix it I've enabled `ignore_stderr` to the testcase on Darwin. Cheers, - Ben