hLookAhead + hSetBuffering = unsupported operation (Illegal seek)
If you compile and run this program, and then press 'a' while it is running:
module Main (main) where
import System.IO
main :: IO ()
main = do hSetBuffering stdin NoBuffering
hLookAhead stdin >>= print
hSetBuffering stdin LineBuffering
then you get (amd64/Linux):
$ ./y
a'a'
y: <stdin>: hSetBuffering: unsupported operation (Illegal seek)
The docs at http://www.haskell.org/ghc/docs/latest/html/libraries/base/System-IO.html\#v%3AhSetBuffering say what happens when setting a buffer to !NoBuffering, but don't give any clue that this can happen when changing to !LineBuffering. I don't know if it is the behaviour or the docs that should be changed.
Also happens in the 6.10 branch.
Trac metadata
Trac field | Value |
---|---|
Version | 6.8.3 |
Type | Bug |
TypeOfFailure | OtherFailure |
Priority | normal |
Resolution | Unresolved |
Component | libraries/base |
Test case | |
Differential revisions | |
BlockedBy | |
Related | |
Blocking | |
CC | |
Operating system | |
Architecture |