Strange buffering behaviour in GHCi
Reported by Clifford Beshers on haskell@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>
Trac metadata
Trac field | Value |
---|---|
Version | 6.5 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | GHCi |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | clifford.beshers@linspire.com |
Operating system | Unknown |
Architecture | Unknown |