Date: Thu, 6 Oct 2011 15:29:49 -0400
From: Christopher Faylor <cgf-use-the-mailinglist-please AT cygwin DOT com>
To: cygwin AT cygwin DOT com
Subject: Re: 1.7.9 Missing SIGPIPE?
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On Thu, Oct 06, 2011 at 08:29:19PM +0200, Marco Atzeri wrote:
>On 10/4/2011 6:39 PM, Christopher Faylor wrote:
>
>> As I mentioned in the thread, that is supposed to be implemented in
>> Cygwin.  I could never see a case where it wasn't sent.
>>
>> cgf
>
>Hi Cgf,
>my understanding of your explanation:
>
>"Sort of.  If the process is doing a read, it is supposed to detect that
>the tty has been closed and a SIGHUP is supposed to be sent.  It is not
>precisely the same thing as sending a SIGHUP when the master closes but
>I'm surprised that, in principle, it doesn't amount to the same thing.
>
>Just see any of the SIGHUPs in fhandler_tty.cc.  They are all supposed
>to be dealing with this scenario.
>
>So, unless bash is not waiting for input (which is unlikely) this should
>work."
>
>was :
>- it is not implemented
>- you see no pratical case were this could be a problem as
>   the program waiting for data should recognize the closure
>   and correctly handling it
>
>Checking fhandler_tty.cc , I see no implementation, but I can be wrong
>as my understanding of cygwin internals is limited.
>
>I admit that mc expectation is a corner case, but the subshell closure 
>was based on such assumption (src/subshell.c)
>
>/* Close master side of pty.  This is important; apart from */
>/* freeing up the descriptor for use in the subshell, it also       */
>/* means that when MC exits, the subshell will get a SIGHUP and     */
>/* exit too, because there will be no more descriptors pointing     */
>/* at the master side of the pty and so it will disappear.  */
>
>so as workaround I added a SIGHUP
>
>     kill (subshell_pid, SIGHUP);
>
>just before mc exit on the main, to simulate the behaviour
>and the subshell closes as needed.
>
>Linux and BSD correctly handle the situation while only cygwin
>was reported missing this behaviour.

I was being imprecise in my response.

I understand what you say you did.  There was no reason to reexplain.

Once again, I don't understand why Cygwin's current implementation is
inadequate to handle the problem that you are seeing.  You can assert
that it must be because Cygwin does not explicitly send a SIGHUP on
close and you may be right but, again, I don't see why the current
implementation, which should amount to the same thing, does not work.

Yes.  It isn't explicitly implemented but it shouldn't matter.

cgf

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