[GHC] #929: Strange buffering behaviour in GHCi

[GHC]

#929: Strange buffering behaviour in GHCi
-------------------------+--------------------------------------------------
    Reporter:  simonmar  |        Owner:         
        Type:  bug       |       Status:  new    
    Priority:  normal    |    Milestone:  6.6.1  
   Component:  GHCi      |      Version:  6.5    
    Severity:  normal    |     Keywords:         
          Os:  Unknown   |   Difficulty:  Unknown
Architecture:  Unknown   |  
-------------------------+--------------------------------------------------
Reported by Clifford Beshers on haskell at haskell.org:

   ghci starts with !NoBuffering behavior, even though the mode appears to
 be
   !LineBuffering.  Setting it once fixes the problem.

   I've included a ghci session that demonstrates the bug by showing the
 change in
   behavior when pressing Control-D in response to each call to getLine.
 The results
   are identical for 6.4.1 and 6.6 rc1.


 {{{
   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.4.1, for Haskell 98.
 / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
 \____/\/ /_/\____/|_|      Type :? for help.

 Loading package base-1.0 ... linking ... done.
 Prelude> :m +System.IO
 Prelude System.IO> hGetBuffering stdin >>= print
 LineBuffering
 Prelude System.IO> getLine >>= print
 ^D
 "\EOT"
 Prelude System.IO> hSetBuffering stdin NoBuffering >> hGetBuffering stdin
 >>= print
 NoBuffering
 Prelude System.IO> getLine >>= print
 ^D
 "\EOT"
 Prelude System.IO> hSetBuffering stdin LineBuffering >> hGetBuffering
 stdin >>= print
 LineBuffering
 Prelude System.IO> getLine >>= print
 *** Exception: <stdin>: hGetLine: end of file
 Prelude System.IO>



   ___         ___ _
  / _ \ /\  /\/ __(_)
 / /_\// /_/ / /  | |      GHC Interactive, version 6.5.20060831, for
 Haskell 98.
 / /_\\/ __  / /___| |      http://www.haskell.org/ghc/
 \____/\/ /_/\____/|_|      Type :? for help.

 Loading package base ... linking ... done.
 Prelude> :m +System.IO
 Prelude System.IO> hGetBuffering stdin >>= print
 LineBuffering
 Prelude System.IO> getLine >>= print
 ^D
 "\EOT"
 Prelude System.IO> hSetBuffering stdin NoBuffering >> hGetBuffering stdin
 >>= print
 NoBuffering
 Prelude System.IO> getLine >>= print
 ^D
 "\EOT"
 Prelude System.IO> hSetBuffering stdin LineBuffering >> hGetBuffering
 stdin >>= print
 LineBuffering
 Prelude System.IO> getLine >>= print
 *** Exception: <stdin>: hGetLine: end of file
 Prelude System.IO>
 }}}

-- 
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/929>
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