[GHC] #7206: Implement cheap build

[GHC]

#7206: Implement cheap build
-------------------------------------+-------------------------------------
              Reporter:  simonpj     |            Owner:  simonpj
                  Type:  bug         |           Status:  new
              Priority:  normal      |        Milestone:  ⊥
             Component:  Compiler    |          Version:  7.4.2
            Resolution:              |         Keywords:
      Operating System:              |     Architecture:  Unknown/Multiple
  Unknown/Multiple                   |       Difficulty:  Unknown
       Type of failure:              |       Blocked By:
  None/Unknown                       |  Related Tickets:
             Test Case:              |
              Blocking:              |
Differential Revisions:              |
-------------------------------------+-------------------------------------
Changes (by snoyberg):

 * cc: snoyberg (added)


Comment:

 Following up on a separate discussion on the haskell-cafe, I have a
 possibly related case:

 {{{#!hs
 main :: IO ()
 main = printLen >> printLen

 printLen :: IO ()
 printLen = lengthM 0 [1..40000000 :: Int] >>= print

 lengthM :: Monad m => Int -> [a] -> m Int
 lengthM cnt [] = return cnt
 lengthM cnt (_:xs) =
     cnt' `seq` lengthM cnt' xs
   where
     cnt' = cnt + 1
 }}}

 On my system, this takes almost 1.2GB of memory. If I comment out the
 second call to `printLen`, it takes 44KB.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/7206#comment:10>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler