Bug#1030909: Unable to run xscreensaver-demo or xscreensaver-settings

[Tormod Volden]

For completeness, here is the backtrace at breakpoint on
XSetInputFocus, on Debian unstable with debug symbols (before
launching gdb, export DEBUGINFOD_URLS="https://debuginfod.debian.net"
).

(gdb) bt full
#0  XSetInputFocus (dpy=0x5555555fda90, focus=focus at entry=41943047,
revert_to=revert_to at entry=2, time=time at entry=0) at
../../src/SetIFocus.c:41
        req = <optimized out>
#1  0x00007ffff7f3678f in gdk_x11_window_focus (window=<optimized
out>, timestamp=0) at ../../../gdk/x11/gdkwindow-x11.c:2326
        display = 0x5555556110f0 [GdkX11Display]
        __func__ = "gdk_x11_window_focus"
#2  0x00007ffff798cfeb in gtk_window_present_with_time
(window=0x5555556e47c0 [XScreenSaverWindow], timestamp=0) at
../../../gtk/gtkwindow.c:10611
        priv = <optimized out>
        widget = 0x5555556e47c0 [XScreenSaverWindow]
        gdk_window = 0x55555595ac30 [GdkX11Window]
        __func__ = "gtk_window_present_with_time"
#3  0x000055555557009d in xscreensaver_app_activate
(app=0x5555555da0f0 [XScreenSaverApp]) at demo-Gtk.c:5321
        win = 0x5555556e47c0 [XScreenSaverWindow]
        debug_p = 1
        dpy = 0x5555555fda90
#4  0x00007ffff70f55a9 in _g_closure_invoke_va
(closure=closure at entry=0x5555555d4400,
return_value=return_value at entry=0x0,
instance=instance at entry=0x5555555da0f0,
args=args at entry=0x7fffffffdc30, n_params=0, param_types=0x0) at
../../../gobject/gclosure.c:895
        marshal = 0x7ffff70f3b60 <g_type_class_meta_marshalv>
        marshal_data = 0x90
        in_marshal = 0
        real_closure = 0x5555555d43e0
        __func__ = "_g_closure_invoke_va"
#5  0x00007ffff710ebbf in g_signal_emit_valist
(instance=0x5555555da0f0, signal_id=8, detail=<optimized out>,
var_args=var_args at entry=0x7fffffffdc30) at
../../../gobject/gsignal.c:3456
        return_accu = <optimized out>
        accu = {g_type = 0x0, data = {{v_int = 0, v_uint = 0, v_long =
0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0,
v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0,
v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer =
0x0}}}
        accumulator = 0x0
        emission = {next = 0x0, instance = 0x5555555da0f0, ihint =
{signal_id = 8, detail = 0, run_type = (G_SIGNAL_RUN_LAST |
G_SIGNAL_ACCUMULATOR_FIRST_RUN)}, state = EMISSION_RUN, chain_type =
0x5555555d2640 [XScreenSaverApp/GtkApplication/GApplication]}
        instance_type = <optimized out>
        emission_return = {g_type = 0x0, data = {{v_int = 0, v_uint =
0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0,
v_double = 0, v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0,
v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0,
v_pointer = 0x0}}}
        rtype = 0x4 [void]
        static_scope = 0
        fastpath_handler = <optimized out>
        closure = <optimized out>
        run_type = <optimized out>
        hlist = <optimized out>
        l = <optimized out>
        fastpath = <optimized out>
        instance_and_params = <optimized out>
        signal_return_type = <optimized out>
        param_values = <optimized out>
        node = <optimized out>
        i = <optimized out>
        n_params = <optimized out>
        __func__ = "g_signal_emit_valist"
#6  0x00007ffff710edbf in g_signal_emit
(instance=instance at entry=0x5555555da0f0, signal_id=<optimized out>,
detail=detail at entry=0) at ../../../gobject/gsignal.c:3606
        var_args = {{gp_offset = 24, fp_offset = 48, overflow_arg_area
= 0x7fffffffdd10, reg_save_area = 0x7fffffffdc50}}
#7  0x00007ffff74ff0c3 in g_application_activate
(application=application at entry=0x5555555da0f0 [XScreenSaverApp]) at
../../../gio/gapplication.c:2312
        __func__ = "g_application_activate"
#8  0x00007ffff74ff438 in g_application_real_local_command_line
(application=0x5555555da0f0 [XScreenSaverApp],
arguments=0x7fffffffdd78, exit_status=0x7fffffffdd74) at
../../../gio/gapplication.c:1148
        error = 0x0
        options = 0x5555555dbfa0
        n_args = 1
#9  0x00007ffff74ff5c6 in g_application_run
(application=0x5555555da0f0 [XScreenSaverApp], argc=<optimized out>,
argv=<optimized out>) at ../../../gio/gapplication.c:2542
        arguments = 0x5555555db710
        status = -1
        context = 0x5555555db770
        acquired_context = <optimized out>
        __func__ = "g_application_run"
#10 0x000055555557040b in main (argc=2, argv=0x7fffffffdf18) at demo-Gtk.c:5398
        s = 0x7fffffffe2a6 "/xscreensaver-settings"
(gdb) c

Note that if I install an empty command (command 1, continue, end) at
the breakpoint, the crash doesn't happen. So it is timing sensitive. I
don't even know if the backtrace corresponds to the request in the
crash, it is the only occurrence of XSetInputFocus when I have a
breakpoint, but maybe it is different without. On another system I see
two occurrences before the window comes up finished.