1 -- This is the mainPrimIO that must be used for Haskell~1.3.
3 module GHCmain ( mainPrimIO ) where
5 import qualified Main -- for type of "Main.main"
8 mainPrimIO :: PrimIO ()
10 mainPrimIO = ST $ \ s ->
11 case Main.main of { IO (ST main_guts) ->
12 case main_guts s of { (result, s2@(S# _)) ->
14 Right () -> ( (), s2 )
15 Left err -> error ("I/O error: "++showsPrec 0 err "\n")
21 Nota Bene! @mainIO@ is written as an explicit function, rather than
22 by saying: @mainIO = requestToIO main@ so that the code generator
23 recognises @mainIO@ as a {\em function} (hence HNF, hence not
24 updatable), rather than a zero-arity CAF (hence updatable). If it is
25 updated, then we have a mega-space leak, because the entire action
26 (@requestToIO main@) is retained indefinitely.
28 (This doesn't waste work because @mainIO@ is only used once.)