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