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