#7936: newStdGen leaks memory when result is not used -----------------------------+---------------------------------------------- Reporter: ryantrinkle | Owner: Type: bug | Status: new Priority: normal | Component: libraries/random Version: 7.6.3 | Keywords: Os: Unknown/Multiple | Architecture: Unknown/Multiple Failure: Runtime crash | Blockedby: Blocking: | Related: -----------------------------+---------------------------------------------- When newStdGen is invoked repeatedly without making any use of the resulting StdGen values, it leaks memory, as in the following: {{{ -- Leaks memory main = forever newStdGen }}} When a random number produced by the result is evaluated, no leak occurs: {{{ -- Does not leak memory main = forever $ do r <- newStdGen evaluate $ fst $ next r }}} However, evaluating the result itself is not sufficient to eliminate the leak: {{{ -- Leaks memory main = forever $ do r <- newStdGen evaluate r }}} After sufficient iterations of newStdGen, subsequent use will cause a stack overflow: {{{ -- Causes stack overflow main = do replicateM 1000000 newStdGen r <- newStdGen evaluate $ fst $ next r }}} -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/7936 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler