#4248: Poor error message when openFile fails to open named pipe
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Reporter: Khudyakov | Owner:
Type: bug | Status: new
Priority: normal | Milestone: 7.0.2
Component: libraries/base | Version: 6.12.3
Keywords: | Testcase:
Blockedby: | Difficulty:
Os: Unknown/Multiple | Blocking:
Architecture: Unknown/Multiple | Failure: None/Unknown
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Comment(by duncan):
Replying to [comment:2 simonmar]:
> Would you like us to try opening the file in blocking mode if non-
blocking mode fails?
I don't think we would want to do that in general for all files, it's hard
to predict what that does for security or atomicity properties.
The linux man page makes the behaviour clear:
{{{
A process can open a FIFO in nonblocking mode. In this case, opening
for read only will succeed even if no-one has opened on the write side
yet, opening for write only will fail with ENXIO (no such device or
address) unless the other end has already been opened.
Under Linux, opening a FIFO for read and write will succeed both in
blocking and nonblocking mode. POSIX leaves this behavior undefined.
This can be used to open a FIFO for writing while there are no readers
available. A process that uses both ends of the connection in order to
communicate with itself should be very careful to avoid deadlocks.
}}}
So, the "does not exist" error is a direct consequence of the `ENXIO`
error code "no such device or address".
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/4248#comment:3>
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