The TERM signal handling in ksmserver invokes functions which
are not async-signal safe, like Qt functions and C++
destructors. Moreover, the signal handling can occur in other than the
main thread, which leads to Qt complaining about functions being
invoked from the wrong thread. Such a crash can be seen in a report of
destructors. Moreover, the signal handling can occur in other than the main thread, which leads to Qt complaining about functions being invoked from the wrong thread. Such a crash can be seen in a report of [[ bug 384316 |https://bugs.kde.org/show_bug.cgi?id=384316 ]].
To fix both of these issues, this change makes the signal handling use
use the self-pipe trick, which signals the need for termination to the
the main thread by writing to a special-purpose file descriptor. The main
loop then takes care of the termination. This is mostly inspired by [[
loop then takes care of the termination. This is mostly inspired by [[ http://doc.qt.io/qt-5/unix-signals.html ]].
Note that `QApplication::quit` already does what we need when destroying
the server, particularly deleting `the_server`/calling `cleanUp()`.
BTW I noticed the code (here and in XIO error handler) makes quite
sure the_server is zeroed. However, other code in ksmserver is not so
keen on checking `the_server` is !0 when using it.