Re: [Gnuplot-info] Weird behaviour of qt and wxt terminals regarding closing of standard output

[Thomas O. <tho...@or...>]

Am Mon, 11 Jun 2012 19:58:07 +0200
schrieb walter harms <wh...@bf...>: 

> I use X11 most times beside postscript :)
> did you try a strace ?

There is no discernible difference in strace between the cases with and without |cat; the end looks like this:

write(5, "@"..., 1)                     = 1
close(5)                                = 0
close(4)                                = 0
rt_sigaction(SIGCHLD, {SIG_DFL, [], SA_RESTORER|SA_NOCLDSTOP, 0x2b262ebb45a0}, {0x2b262e344aa0, [], SA_RESTORER|SA_NOCLDSTOP, 0x2b262ebb45a0}, 8) = 0
write(3, "\1\0\0\0\0\0\0\0"..., 8)      = 8
close(7)                                = 0
exit_group(0)                           = ?

(That's without following forks ... as I gather that I'm rather concerned with the main process.)

I also see that a gnuplot_qt process keeps hanging around after Ctrl+C-ing the console. It hangs in poll()

Loaded symbols for /usr/lib/libtiff.so.3
0x00002b162a6ced6f in *__GI___poll (fds=0x11152f0, nfds=3, timeout=24463) at ../sysdeps/unix/sysv/linux/poll.c:83
83      ../sysdeps/unix/sysv/linux/poll.c: No such file or directory.
        in ../sysdeps/unix/sysv/linux/poll.c
(gdb) where
#0  0x00002b162a6ced6f in *__GI___poll (fds=0x11152f0, nfds=3, timeout=24463) at ../sysdeps/unix/sysv/linux/poll.c:83
#1  0x00002b16299aec2b in g_main_context_iterate (context=0x10b4f00, block=<value optimized out>, dispatch=1) at gmain.c:3613
#2  0x00002b16299aed5f in g_main_context_iteration (context=0x10b4f00, may_block=1) at gmain.c:3613
#3  0x00002b1628afc872 in QEventDispatcherGlib::processEvents () from /usr/lib/libQtCore.so.4
#4  0x00002b1627f8c422 in ?? () from /usr/lib/libQtGui.so.4
#5  0x00002b1628ad4bd8 in QEventLoop::processEvents () from /usr/lib/libQtCore.so.4
#6  0x00002b1628ad4d8d in QEventLoop::exec () from /usr/lib/libQtCore.so.4
#7  0x00002b1628ad8599 in QCoreApplication::exec () from /usr/lib/libQtCore.so.4
#8  0x000000000040cb48 in main (argc=1, argv=<value optimized out>)


Well, the Wx terminal also sits in poll, simply because that's the main even loop, I suppose. No difference to Qt there (just that it also succeeds in updating the coordinates).


Alrighty then,

Thomas