More on allocateExec... I see this at the end of ./ghc/compiler/ghci/ ByteCodeItbls.lhs foreign import ccall unsafe "allocateExec" _allocateExec :: CUInt -> IO (Ptr a) malloc_exec :: Int -> IO (Ptr a) malloc_exec bytes = _allocateExec (fromIntegral bytes) It does not appear that malloc_exec is used anywhere else but here it's used in the function below. I don't know where allocateExec is supposed to be coming from. -- Assumes constructors are numbered from zero, not one make_constr_itbls :: [DataCon] -> IO ItblEnv make_constr_itbls cons | listLengthCmp cons 8 /= GT -- <= 8 elements in the list = do is <- mapM mk_vecret_itbl (zip cons [0..]) return (mkItblEnv is) | otherwise = do is <- mapM mk_dirret_itbl (zip cons [0..]) return (mkItblEnv is) where mk_vecret_itbl (dcon, conNo) = mk_itbl dcon conNo (vecret_entry conNo) mk_dirret_itbl (dcon, conNo) = mk_itbl dcon conNo stg_interp_constr_entry mk_itbl :: DataCon -> Int -> Ptr () -> IO (Name,ItblPtr) mk_itbl dcon conNo entry_addr = let rep_args = [ (typeCgRep arg,arg) | arg <- dataConRepArgTys dcon ] (tot_wds, ptr_wds, _) = mkVirtHeapOffsets rep_args ptrs = ptr_wds nptrs = tot_wds - ptr_wds nptrs_really | ptrs + nptrs >= mIN_SIZE_NonUpdHeapObject = nptrs | otherwise = mIN_SIZE_NonUpdHeapObject - ptrs itbl = StgInfoTable { ptrs = fromIntegral ptrs, nptrs = fromIntegral nptrs_really, tipe = fromIntegral cONSTR, srtlen = fromIntegral conNo, code = code } -- Make a piece of code to jump to "entry_label". -- This is the only arch-dependent bit. code = mkJumpToAddr entry_addr in do addr <- malloc_exec (sizeOf itbl) --putStrLn ("SIZE of itbl is " ++ show (sizeOf itbl)) --putStrLn ("# ptrs of itbl is " ++ show ptrs) --putStrLn ("# nptrs of itbl is " ++ show nptrs_really) poke addr itbl return (getName dcon, addr `plusPtr` (2 * wORD_SIZE))