[darcs-users] bug report: "Fail: <stdin>: hSetBuffering: unsupported operation (Illegal seek)"
darcs at davidb.org
Fri May 7 16:03:52 UTC 2004
On Fri, May 07, 2004 at 06:56:16AM -0400, David Roundy wrote:
> > Fail: <stdin>: hSetBuffering: unsupported operation (Illegal seek)
> I haven't been able to reproduce this. I know I've seen it before though.
> :( So if you (or anyone else) has a suggestion how I could reproduce (and
> therefore fix, or at least identify) this bug, that would be great.
It is a GHC library bug, but it is mentioned in a TODO in the source.
hSetBuffering: can't change buffering on a stream,
when the read buffer is non-empty? (no way to flush the buffer)
It likely happens when you change to or from unbuffered mode and there
are already characters typed ahead. The seek isn't supposed to happen
on a tty, though. It is trivial to reproduce:
module Main where
main :: IO ()
main = do
hSetBuffering stdin NoBuffering
Build this, run it, and just type a few characters on stdin, and press
What's real interesting is that this doesn't break on OSX (both have
6.2 of ghc).
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