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List:       kde-devel
Subject:    Re: libksane seems to break QProcess::start calls
From:       Stefan =?ISO-8859-1?Q?Br=FCns?= <stefan.bruens () rwth-aachen ! de>
Date:       2022-03-03 18:06:21
Message-ID: 3518690.cikN3laI15 () pebbles
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On Donnerstag, 3. März 2022 13:54:32 CET Tobias Leupold wrote:
> Hi all :-)
> 
> I have a very odd problem, and I have no idea what could cause this or even
> how to debug this. maybe, someone of you can give me a hint.
> 
> I revently wrote a small helper program for one special purpose: Scanning
> documents at a defined size, post processing them a bit and saving the
> processed, compressed images as a PDF file to e.g. send them via mail. The
> sources can be found at https://invent.kde.org/tleupold/scandoc/ .

Are you using either Qt5 < 5.15 or a kernel version which does not support 
CLONE_FD? - then you are relying on SIGCHLD for process exit notification.

CLONE_FD: https://lwn.net/Articles/636646/
Qt5: https://codereview.qt-project.org/c/qt/qtbase/+/108456/

sane-backends/backend/plustek-usbhw.c messes with the signal handlers and 
fails to restore it: `sigaction(..., ..., NULL)`


Regards, Stefan

-- 
Stefan Brüns  /  Bergstraße 21  /  52062 Aachen
home: +49 241 53809034     mobile: +49 151 50412019
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