#12566: Memory leak -------------------------------------+------------------------------------- Reporter: igloo | Owner: Type: bug | Status: new Priority: normal | Milestone: Component: Compiler | Version: 8.0.1 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: -------------------------------------+------------------------------------- With the attached write.hs (which generates a file called "data") and read.hs (which consumes that file), if I run {{{ ghc -Wall -Werror -O write.hs -o write ghc -Wall -Werror -O -prof -auto-all read.hs -o read1 ghc -Wall -Werror -O -prof -auto-all read.hs -o read2 -DLEAK ./write ./read1 +RTS -h ./read2 +RTS -h }}} then read2's heap profile shows that it is retaining a lot of extra data. Perhaps I am missing something, but I can't see why this needs to be retained. I would expect the two heap profiles to look the same. Sources and heap profiles (using GHC 8.0.1) attached. I've copied the sources below for convenience: write.hs: {{{#!hs module Main (main) where import qualified Data.ByteString.Lazy.Char8 as L main :: IO () main = L.writeFile "data" $ L.concat $ map mkByteString [1..100000] mkByteString :: Int -> L.ByteString mkByteString i = L.concat (L.pack ("#" ++ show i ++ "\n") : replicate 100 (L.pack "Something else\n")) }}} read.hs: {{{#!hs {-# LANGUAGE BangPatterns, CPP #-} module Main (main) where import Data.List import Data.Set (Set) import qualified Data.Set as Set import qualified Data.ByteString.Char8 as S import qualified Data.ByteString.Lazy.Char8 as L main :: IO () main = do bs <- L.readFile "data" let stats = getMaybes bs s = mkSet stats print $ Set.size s mkSet :: [Maybe S.ByteString] -> Set S.ByteString mkSet ms = foldl' f Set.empty ms where f s (Just l) = Set.insert l s f s _ = s getMaybes :: L.ByteString -> [Maybe S.ByteString] getMaybes bs = if L.null bs then [] else case getMaybe bs of (stat, bs') -> stat : getMaybes bs' getMaybe :: L.ByteString -> (Maybe S.ByteString, L.ByteString) getMaybe bs = case L.uncons bs of Just ('#', bs') -> case L.break ('\n' ==) bs' of (l, bs'') -> let !l' = copy l in (Just l', bs'') _ -> case L.break ('\n' ==) bs of (_x, bs') -> #ifdef LEAK copy _x `seq` #endif (Nothing, L.tail bs') copy :: L.ByteString -> S.ByteString copy bs = S.copy $ L.toStrict bs }}} -- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/12566 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler