ghc and ghci differs in deailing with "undefined" with I/O

[guest]

This program:

main = putStrLn ("x == " ++ undefined)

produces the following expected output with ghci:

x == *** Exception: Prelude.undefined

but when compiled with ghc and run, it gives:

$./a.out 
a.out: Prelude.undefined

we observed this in all the way back to ghc6.2.1; possibly earlier.

The semantics of error reporting in combination with I/O is murky; admittedly laziness is observable at the top-level when errors are reported. But at least ghc and ghci should do the same thing. And the behavior of ghci seems to be more appropriate.

Thanks!

Jeff Lewis and Levent Erkok

[neil]

Is this not just line buffering versus character buffer? Try hSetBuffering and I think these will have the same behaviour. (Apart from giving the program name versus Exception)

[guest]

apologies; false alarm while trying to track down some other issue!

this isn't a bug.