[GHC] #14379: GHC 2.8.1 Consumes All Memory On Build

21 Oct 2017

      #14379: GHC 2.8.1 Consumes All Memory On Build
-------------------------------------+-------------------------------------
           Reporter:  jm4games       |             Owner:  (none)
               Type:  bug            |            Status:  new
           Priority:  high           |         Milestone:
          Component:  Compiler       |           Version:  8.2.1
           Keywords:                 |  Operating System:  Linux
       Architecture:  x86_64         |   Type of failure:  Compile-time
  (amd64)                            |  crash or panic
          Test Case:                 |        Blocked By:
           Blocking:                 |   Related Tickets:
Differential Rev(s):                 |         Wiki Page:
-------------------------------------+-------------------------------------
 The following code will cause GHC to consume all memory/swap and
 eventually crash.

 {{{
 #!div style="font-size: 80%"
 Code highlighting:
   {{{#!haskell
 module Test.Test where

 import Data.Text (Text)

 import Data.Monoid ((<>))
 import Data.Vector as V
 import TextShow (showt)

 compileTest :: V.Vector (Text, V.Vector (Int, V.Vector a)) -> V.Vector
 (Text, V.Vector (Int, V.Vector a)) -> Either Text ()
 compileTest vecA vecB = V.ifoldl' validateSym (Right ()) vecB
   where
     validateSym :: Either Text () -> Int -> (Text, V.Vector (Int, V.Vector
 a)) -> Either Text ()
     validateSym res iSym (sym, freqs)
       | Just sym == (fst <$> (vecA V.!? iSym)) = V.ifoldl' validateFreq
 res freqs
       | otherwise = Left $
             if iSym < V.length vecA then
               "Seed data" <> " not found at index [" <> showt iSym <> "]."
               else "No " <> sym <> " at index " <> showt iSym <> "."
       where
         validateFreq :: Either Text () -> Int -> (Int, V.Vector a) ->
 Either Text ()
         validateFreq res2 iFreq (freq, _)
           | freq == fst (snd (vecA V.! iSym) V.! iFreq) = res2
           | otherwise = Left $
                 "Seed data " <> (fst (vecA V.! iSym)) <>
                 " at frequency " <> showt (fst (snd (vecA V.! iSym) V.!
 iFreq)) <>
                 " not found at index [" <> showt iSym <> "][" <> showt
 iFreq -- <> "]."
   }}}
 }}}

 NOTE: The snippet is large (and messy) because there seems to be an exact
 sequence of evaluation to causing the out of memory. For example if you
 comment out line 26 (<> showt iFreq) it will allow the code to compile.
 Like wise if I comment out all of line 25 it will compile. I can't seem to
 figure out what exact combination of things causes the issue.

 Cabal file (used with stack 1.5.1, resolver: nightly-2017-10-21).
 {{{
 #!div style="font-size: 80%"
 Code highlighting:
   {{{#!text
 name:                some-test
 version:             0.2.1.0
 build-type:          Simple
 cabal-version:       >= 1.10

 library
   default-language: Haskell2010
   ghc-options:      -Wall -fwarn-tabs -funbox-strict-fields -fno-warn-
 unused-do-bind -O2
   ghc-prof-options: -fprof-auto

   exposed-modules:
     Test.Test

   build-depends:
     base                    >= 4.9   && < 4.11,
     text                    >= 1.2,
     text-show               >= 3.4   && < 3.7,
     vector                  >= 0.10  && < 0.13

   default-extensions:
     OverloadedStrings
   }}}
 }}}

-- 
Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/14379
GHC http://www.haskell.org/ghc/
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