[GHC] #10830: maximumBy has a space leak

[GHC]

#10830: maximumBy has a space leak
-------------------------------------+-------------------------------------
              Reporter:              |             Owner:
  NeilMitchell                       |
                  Type:  bug         |            Status:  new
              Priority:  normal      |         Milestone:
             Component:              |           Version:  7.10.2
  libraries/base                     |
              Keywords:              |  Operating System:  Windows
          Architecture:              |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
             Test Case:              |        Blocked By:
              Blocking:              |   Related Tickets:
Differential Revisions:              |
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 Given the program:

 {{{#!hs
 import Data.List
 main = print $ maximumBy compare [1..10000]
 }}}

 Compiling with {{{-O2}}}, on GHC 7.8.3 this runs in constant stack space
 (works fine with {{{+RTS -K1K}}}). With GHC 7.10.2 I get:

 {{{
 $ ghc --make Test.hs -O2 -rtsopts
 [1 of 1] Compiling Main             ( Test.hs, Test.o )
 Linking Test.exe ...

 $ Test +RTS -K100K
 Stack space overflow: current size 33680 bytes.
 Use `+RTS -Ksize -RTS' to increase it.
 }}}

 Not sure why it's failing at 33K instead of 100K, but it's certainly
 taking more than 1K as GHC 7.8.3 did.

 See #3416 for previous discussion of this issue. My guess is that in older
 versions of GHC the strictness analysis managed to kick in and optimise
 things. With the burnt bridges that no longer works.

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/10830>
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