OS X GHC build has these test failures: Unexpected failures: cabal/sigcabal01 sigcabal01 [bad stderr] (normal) driver/retc001 retc001 [bad stderr] (normal) ffi/should_run T2276_ghci [bad exit code] (ghci) rts linker_unload [bad exit code] (normal) th T10019 [bad stdout] (ghci) th T10279 [stderr mismatch] (normal) typecheck/should_fail T10534 [stderr mismatch] (normal) sigcabal01 looks like tests that depend on generated names or offsets that are just different under OS X retc001 - test looks busted to me: Does GHC now exit with a process error code of non-zero when compilation fails? If so, the Makefile needs fixing. T2276_ghci - looks like -Wignored-attributes broke this test? linker_unload - malloc.h is in malloc/malloc.h under OS X (!) T10019 - magic generated symbol in "golden" test out is wrong: 'a_1627391544' vs. 'a_1627391540' T10279 - panic! (the 'impossible' happened) gual_pkg rts-1.0 T10534 - text message punctation change There were also a bunch of performance deviations - but they were mostly just out of bounds or wildly different (over by 100%.... under by 50%!)