On Sun, Oct 09, 2011 at 03:30:20PM +0200, Jean-Marie Gaillourdet wrote:
Hi Daniel,
On 09.10.2011, at 14:45, Daniel Fischer wrote:
On Sunday 09 October 2011, 13:52:47, Jean-Marie Gaillourdet wrote:
This seems to be a Heisenbug as it is extremely fragile, when adding a
"| grep 1" to the while loop it seems to disappears. At least on my
computers.
Still produces 1s here with a grep.
Well, it may have been bad luck on my site.
The program below will occasionally print "1 /= 0" or "0 /= 1" on
x86_64 linux with the Debian testing 7.0.4 ghc.
$ ghc bug -rtsopts -threaded
$ while true; do ./bug +RTS -N; done
module Main where
import Control.Monad
import Control.Concurrent
import Data.Typeable
main :: IO ()
main = do
fin1 <- newEmptyMVar
fin2 <- newEmptyMVar
forkIO $ child fin1
forkIO $ child fin2
a <- takeMVar fin1
b <- takeMVar fin2
when (a /= b) $
putStrLn $ show a ++ " /= " ++ show b
child :: MVar Int -> IO ()
child var = do
key <- typeRepKey (typeOf ())
putMVar var key
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