[Haskell-cafe] Re: sendfile leaking descriptors on Linux?

[Felipe Lessa]

On Sat, Feb 06, 2010 at 09:16:35AM +0100, Bardur Arantsson wrote:
> Brandon S. Allbery KF8NH wrote:
> >On Feb 5, 2010, at 02:56 , Bardur Arantsson wrote:
> [--snip--]
> >
> >"Broken pipe" is normally handled as a signal, and is only mapped
> >to an error if SIGPIPE is set to SIG_IGN.  I can well imagine that
> >the SIGPIPE signal handler isn't closing resources properly; a
> >workaround would be to use the System.Posix.Signals API to ignore
> >SIGPIPE, but I don't know if that would work as a general solution
> >(it would depend on what other uses of pipes/sockets exist).
>
> It was a good idea, but it doesn't seem to help to add
>
> 	installHandler sigPIPE Ignore (Just fullSignalSet)
>
> to the main function. (Given the package name I assume
> System.Posix.Signals works similarly to regular old signals, i.e.
> globally per-process.)
>
> This is really starting to drive me round the bend...

Have you seen GHC ticket #1619?

http://hackage.haskell.org/trac/ghc/ticket/1619


> One further thing I've noticed: When compiling on my 64-bit machine,
> ghc issues the following warnings:
>
> Linux.hsc:41: warning: format ‘%d’ expects type ‘int’, but argument
> 3 has type ‘long unsigned int’
> Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument
> 3 has type ‘long unsigned int’
> Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument
> 3 has type ‘long unsigned int’
> Linux.hsc:45: warning: format ‘%d’ expects type ‘int’, but argument
> 3 has type ‘long unsigned int’
>
> Those lines are:
>
> 39: -- max num of bytes in one send
> 40: maxBytes :: Int64
> 41: maxBytes = fromIntegral (maxBound :: (#type ssize_t))
>
> and
>
> 44: foreign import ccall unsafe "sendfile64" c_sendfile
> 45:   :: Fd -> Fd -> Ptr (#type off_t) -> (#type size_t) -> IO
> (#type ssize_t)
>
> This looks like a typical 32/64-bit problem, but normally I would
> expect any real run-time problems caused by a problematic conversion
> in the FFI to crash the whole process. Maybe I'm wrong about this...

To convert those '#' constants, hsc2hs preprocessor constructs a
C file things like 'printf("%d", sizeof(ssize_t))' to use the
system's C compiler and avoid having the encode the ABI of every
platform (to be able to know the memory layout of the
structures).

So that message comes from that C file, not from your Haskell
one.  At runtime it really doesn't matter.

--
Felipe.