Re: Regression (last snapshot)

[Eric Blake <eblake@redhat.com>]

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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?
> 
> It does happen in the current release, as I said earlier in the thread.
> 
> There's no way to test it on Linux.  xwin-xdg-menu is a Cygwin-specific 
> 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.
> 
> Take a look at the bash source code and the grep source code.  You'll 
> see that neither one of them does this.  And I don't know why you would 
> 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.

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


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