Hi, After a long fight, I found that this is a bug of the "-O2" option of GHC head on 32bit machine. Now, it is easy to reproduce this segfault. Please read and try this: https://github.com/kazu-yamamoto/buggy-psq Note that this segfault does not occur when "-O' is specified. --Kazu

Hi,

threadDelay of GHC head causes seqfault or bus error on 32bit machine including Mac and Linux. This bug does not exist as least in GHC 7.4.2.

This bug is due to atMost of GHC.Event.PSQ. After modifying libraries/base/base.cabal to export GHC.Event and building GHC head, the following code (compiled by the GHC head with -threaded) causes segfault or bus error:

main :: IO () main = do s <- newSource ents <- replicateM 100 (entry s) let q = fold ents print $ Q.atMost 1.5 q

fold :: [(Q.Key, Q.Prio)] -> Q.PSQ () fold [] = Q.empty fold ((u,r):xs) = Q.insert u r () $ fold xs

entry :: UniqueSource -> IO (Q.Key, Q.Prio) entry s = do u <- newUnique s r <- randomIO return (u,r)

But if I copy GHC.Event.PSQ and GHC.Event.Unique, modify their module names, and compile the above code with them, no segfault/bus error happens.

I have been tracking this for a long time but I have no idea why this happens. Any advice would be highly appreciated.

For more information, please refer to:

http://hackage.haskell.org/trac/ghc/ticket/7715

--Kazu