#8383: "tagToEnum# (0# ==# 1#) :: Bool" causes CASEFAIL in ghci ---------------------------------+---------------------------------- Reporter: rwbarton | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: GHCi | Version: 7.7 Resolution: | Keywords: Operating System: Linux | Architecture: x86_64 (amd64) Type of failure: None/Unknown | Difficulty: Unknown Test Case: | Blocked By: Blocking: | Related Tickets: ---------------------------------+---------------------------------- Comment (by rwbarton): {{{ -- Compile code which expects an unboxed Int on the top of stack, -- (call it i), and pushes the i'th closure in the supplied list -- as a consequence. implement_tagToId :: [Name] -> BcM BCInstrList implement_tagToId names = ASSERT( notNull names ) do labels <- getLabelsBc (genericLength names) label_fail <- getLabelBc label_exit <- getLabelBc let infos = zip4 labels (tail labels ++ [label_fail]) [0 ..] names steps = map (mkStep label_exit) infos return (concatOL steps `appOL` toOL [LABEL label_fail, CASEFAIL, LABEL label_exit]) where mkStep l_exit (my_label, next_label, n, name_for_n) = toOL [LABEL my_label, TESTEQ_I n next_label, PUSH_G name_for_n, JMP l_exit] }}} This code is wrong, because `TESTEQ_I` expects a boxed Int on top of the stack. A silly but working fix is to `schemeT`: {{{ #!diff schemeT d s p app -- | trace ("schemeT: env in = \n" ++ showSDocDebug (ppBCEnv p)) False -- = panic "schemeT ?!?!" -- | trace ("\nschemeT\n" ++ showSDoc (pprCoreExpr (deAnnotate' app)) ++ "\n") False -- = error "?!?!" -- Case 0 | Just (arg, constr_names) <- maybe_is_tagToEnum_call = do (push, arg_words) <- pushAtom d p arg tagToId_sequence <- implement_tagToId constr_names - return (push `appOL` tagToId_sequence - `appOL` mkSLIDE 1 (d - s + fromIntegral arg_words) + return (push `appOL` push `appOL` tagToId_sequence + `appOL` mkSLIDE 1 (d - s + fromIntegral arg_words + 1) `snocOL` ENTER) }}} Obviously, it would be more sensible to grab the actual info pointer for Int and push that instead of a second copy of the unboxed Int. -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/8383#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler