source: trunk/doc/src/howtos/unix-signal-handlers.qdoc

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/*!
    \page unix-signals.html
    \title Calling Qt Functions From Unix Signal Handlers
    \brief You can't. But don't despair, there is a way...

    \ingroup platform-specific
    \ingroup best-practices

    You \e can't call Qt functions from Unix signal handlers. The
    standard POSIX rule applies: You can only call async-signal-safe
    functions from signal handlers. See \l
    {http://www.opengroup.org/onlinepubs/000095399/functions/xsh_chap02_04.html#tag_02_04_01}
    {Signal Actions} for the complete list of functions you can call
    from Unix signal handlers.

    But don't despair, there is a way to use Unix signal handlers with
    Qt. The strategy is to have your Unix signal handler do something
    that will eventually cause a Qt signal to be emitted, and then you
    simply return from your Unix signal handler. Back in your Qt
    program, that Qt signal gets emitted and then received by your Qt
    slot function, where you can safely do whatever Qt stuff you
    weren't allowed to do in the Unix signal handler.

    One simple way to make this happen is to declare a socket pair in
    your class for each Unix signal you want to handle. The socket
    pairs are declared as static data members. You also create a
    QSocketNotifier to monitor the \e read end of each socket pair,
    declare your Unix signal handlers to be static class methods, and
    declare a slot function corresponding to each of your Unix signal
    handlers. In this example, we intend to handle both the SIGHUP and
    SIGTERM signals. Note: You should read the socketpair(2) and the
    sigaction(2) man pages before plowing through the following code