[Haskell-cafe] Reporting a problem with binary-0.5

4 Jun 2010

I've been trying to get in touch with the maintainers of the Binary 
package, to report an issue.  When I emailed the addresses given on 
Hackage, I got an automated response saying I had used an address that 
was no longer current.

I don't want to put pressure on anyone to fix my bug -- I didn't pay 
anything for Binary, so it wouldn't be fair for me to have that kind of 
expectation.  At the same time, I don't really want my bug report to go 
missing just because someone's email address has changed.  Does anyone 
know who I should be talking to?  Or is there a bug tracker for the 
Hackage packages somewhere?

I noticed this problem when I ran into some trouble with the network-dns 
package.  It would hang up as soon as I tried to send a query. 
Eventually I traced the problem to the binary module, and reduced it to 
this short test case:

module Main where

import qualified Data.Binary.Get as G
import qualified Data.ByteString.Lazy as B

main = do
   urandom <- B.readFile "/dev/urandom"
   let urandomParser :: G.Get [Int]
       urandomParser = do
         v <- G.getWord32be
         rest <- urandomParser
         return $ fromIntegral v : rest
       seeds = G.runGet urandomParser urandom

   print $ take 4 seeds

This code attempts to create an infinite list of random numbers -- a 
technique also used by network-dns.  It turns out that this code works 
with binary-0.4.4 but not with binary-0.5.0.2.  Both were built with 
ghc-6.12.1 on Ubuntu.  (I haven't tested with the intermediate versions 
of the binary module.)  It seems that with binary-0.5.0.2 there is some 
unwanted strictness; something is evaluated for the whole list, even 
though it is only the first few elements that are required.

Incidentally, if the test case is changed like this:

--- get_monad.hs        2010-05-28 11:31:02.399202535 +0100
+++ get_monad2.hs       2010-05-28 13:44:25.515486013 +0100
@@ -1,10 +1,12 @@
  module Main where

+import Control.Monad
+
  import qualified Data.Binary.Get as G
  import qualified Data.ByteString.Lazy as B

  main = do
-  urandom <- B.readFile "/dev/urandom"
+  urandom <- liftM (B.take 64) $ B.readFile "/dev/urandom"
    let urandomParser :: G.Get [Int]
        urandomParser = do
          v <- G.getWord32be

the program exits with an error:

get_monad2.hs: too few bytes. Failed reading at byte position 68

This seems to demonstrate that the program is reading more data than it 
needs to.

Thanks,
Pete

    

[Haskell-cafe] Reporting a problem with binary-0.5

Pete Chown