[GHC] #12205: Program develops space leak with -fprof-auto

[GHC]

#12205: Program develops space leak with -fprof-auto
-------------------------------------+-------------------------------------
           Reporter:  kristenk       |             Owner:
               Type:  bug            |            Status:  new
           Priority:  normal         |         Milestone:
          Component:  Profiling      |           Version:  7.4.2
           Keywords:                 |  Operating System:  Unknown/Multiple
       Architecture:                 |   Type of failure:  None/Unknown
  Unknown/Multiple                   |
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 This program seems to use constant memory when compiled with only `-prof`,
 but it uses increasing amounts of memory when compiled with `-prof` and
 `-fprof-auto`.  I observed the behavior with GHC 8.0.1, 7.10.3, 7.8.4,
 7.6.3, and 7.4.2, but not 7.0.4 (with `-auto-all`).

 {{{#!hs
 import System.Environment

 main :: IO ()
 main = do
   n <- (read . head) `fmap` getArgs
   case f [0..(n::Int)] 0 of
     (xs, s) -> print xs >> print s

 f :: [Int] -> Int -> ([Int], Int)
 f [] s = ([], s)
 f (x:xs) s =
   let (xs', s') = f xs (x + s)
   in (x + s : xs', s')
 }}}

 {{{
 $ ghc --version
 The Glorious Glasgow Haskell Compilation System, version 8.0.1

 $ ghc Main.hs -prof
 [1 of 1] Compiling Main             ( Main.hs, Main.o )
 Linking Main ...

 $ /run/current-system/sw/bin/time ./Main 5000000 > /dev/null
 2.80user 0.01system 0:02.82elapsed 100%CPU (0avgtext+0avgdata
 6028maxresident)k
 0inputs+0outputs (0major+661minor)pagefaults 0swaps
 }}}
 {{{
 $ ghc Main.hs -prof -fprof-auto
 [1 of 1] Compiling Main             ( Main.hs, Main.o )
 Linking Main ...

 $ /run/current-system/sw/bin/time ./Main 5000000 > /dev/null
 4.03user 0.35system 0:04.38elapsed 100%CPU (0avgtext+0avgdata
 1574348maxresident)k
 0inputs+0outputs (0major+392857minor)pagefaults 0swaps
 }}}


 [[Image(no-fprof-auto.png)]]
 [[Image(fprof-auto.png)]]

--
Ticket URL: <http://ghc.haskell.org/trac/ghc/ticket/12205>
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