runProcess hangs with duplicate handles

runProcess doesn't seem to allow the same handle to be
used for redirecting stdout and stderr. Thus,

main = 
  do
    h  <- openFile "output" WriteMode
    ph <- runProcess "/bin/ls" [] Nothing Nothing
               Nothing (Just h) (Just h)
    waitForProcess ph
    return ()

hangs in ghci and aborts with "thread blocked
indefinitely" if compiled.   This isn't documented and
I hope this is not the intended behaviour as
redirecting stdout and stderr (and stdin in the case of
ptys) to the same file/pipe is quite common.

System is Linux 2.4.20-8 #1 Thu Mar 13 17:54:28 EST
2003 i686
ghc is vanilla 6.4

Trac metadata

Trac field	Value
Version	6.4
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	ResolvedFixed
Component	libraries/base
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