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Subject: Re: Regression (last snapshot)
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References: <20190729134700 DOT GO11632 AT calimero DOT vinschen DOT de> <ced2750a-0a52-1396-b6c1-f4228116bde7 AT cornell DOT edu> <20190729152327 DOT GQ11632 AT calimero DOT vinschen DOT de> <20190729154049 DOT GR11632 AT calimero DOT vinschen DOT de> <c5d01965-80b9-cece-54d2-f7462f84c0a2 AT cornell DOT edu> <8e57d4da-722d-1b9a-bd28-5f96ed182f6a AT cornell DOT edu> <0a09679b-1a0f-613b-04c8-1a63da8a00c2 AT cornell DOT edu> <33aead20-540c-ee3b-0d38-ff053fbac040 AT dronecode DOT org DOT uk> <12269538-c387-1f1e-ab5a-b36b60d09937 AT cornell DOT edu> <a61264b5-80da-52fc-7093-8e8d9a8ace33 AT redhat DOT com> <20190801160440 DOT GC11632 AT calimero DOT vinschen DOT de> <19e73527-cb9a-a106-a57a-2895b8a520c9 AT cornell DOT edu> <e922144a-1f02-9398-4223-dbf76c69231f AT cornell DOT edu> <b4d57d88-3ec4-939f-c591-e50aaef607f3 AT cornell DOT edu> <5f4a0400-a173-1948-6048-69ba54df2571 AT SystematicSw DOT ab DOT ca> <400eebe3-3ba9-5448-85a8-92e6e0dfdf0c AT cornell DOT edu>
From: Eric Blake <eblake AT redhat DOT com>
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Date: Fri, 2 Aug 2019 16:58:15 -0500
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From: Eric Blake <eblake AT redhat DOT com>
To: cygwin AT cygwin DOT com
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Subject: Re: Regression (last snapshot)
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On 8/2/19 4:53 PM, Ken Brown wrote:

>>> Putting this all together, Eric's explanation is indeed correct.  All
>>> processes created by xwin-xdg-menu via fork/exec inherit the property of
>>> ignoring SIGPIPE.
>>>
>>> I don't know if this is a bug, but it certainly leads to surprising
>>> behavior.  Jon, maybe xwin-xdg-menu needs to call signal(SIGPIPE,
>>> SIG_DFL) either after calling gtk_init() or before calling exec()?
>>
>> How does that relate to this only happening in the latest snapshot, and =
not in
>> the current release, or any Linux system?
>=20
> It does happen in the current release, as I said earlier in the thread.
>=20
> There's no way to test it on Linux.  xwin-xdg-menu is a Cygwin-specific=
=20
> program (written by Jon).

>> I would certainly expect any shell (or any other program handling pipes)=
 to set
>> or reset SIGPIPE handling, rather than accept any default.
>=20
> Take a look at the bash source code and the grep source code.  You'll=20
> see that neither one of them does this.  And I don't know why you would=
=20
> expect it.

Worse, POSIX explicitly requires that the shell is unable to reset
SIGPIPE back to SIG_DFL if it was inherited ignored (try it - you CANNOT
use the 'trap' command to undo an inherited ignored SIGPIPE, even though
it can be used to undo signals ignored locally). It is generally
considered bad practice to leak ignored SIGPIPE into a child process,
even if it makes sense in the parent process.

--=20
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3226
Virtualization:  qemu.org | libvirt.org


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