The stacktrace (nothing that useful, checking if the workarounds for SGX are interfering at the results):

(gdb) bt full
#0  0xb6373ab4 in XFilterEvent (ev=0xbefff37c, window=<optimized out>) at ../../src/FilterEv.c:91
        p = <optimized out>
        win = 0
        mask = 0
        ret = <optimized out>
#1  0xb6a2aed6 in QApplication::x11ProcessEvent (this=0xbefff5a8, event=0xbefff37c) at kernel/qapplication_x11.cpp:3440
        keywidget = <optimized out>
        grabbed = <optimized out>
        loopLevelCounter = {threadData = 0x1bb88}
        isXI2Event = false
        widget = 0x0
        d = 0x1ba88
        instance = {display = 0x370b8, cookie = 0xbefff37c}
#2  0xb6a451e6 in x11EventSourceDispatch (s=0x21150, callback=0, user_data=0x0) at kernel/qguieventdispatcher_glib.cpp:146
        event = {type = 74, xany = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0}, xkey = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, root = 0, subwindow = 0, time = 0, x = 0, y = 0, 
            x_root = 0, y_root = 0, state = 0, keycode = 0, same_screen = 0}, xbutton = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, root = 0, subwindow = 0, time = 0, x = 0, y = 0, x_root = 0, y_root = 0, 
            state = 0, button = 0, same_screen = 0}, xmotion = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, root = 0, subwindow = 0, time = 0, x = 0, y = 0, x_root = 0, y_root = 0, state = 0, is_hint = 0 '\000', 
            same_screen = 0}, xcrossing = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, root = 0, subwindow = 0, time = 0, x = 0, y = 0, x_root = 0, y_root = 0, mode = 0, detail = 0, same_screen = 0, focus = 0, 
            state = 0}, xfocus = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, mode = 0, detail = 0}, xexpose = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, x = 0, y = 0, width = 0, 
            height = 0, count = 0}, xgraphicsexpose = {type = 74, serial = 0, send_event = 0, display = 0x0, drawable = 0, x = 0, y = 0, width = 0, height = 0, count = 0, major_code = 0, minor_code = 0}, xnoexpose = {type = 74, 
            serial = 0, send_event = 0, display = 0x0, drawable = 0, major_code = 0, minor_code = 0}, xvisibility = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, state = 0}, xcreatewindow = {type = 74, serial = 0, 
            send_event = 0, display = 0x0, parent = 0, window = 0, x = 0, y = 0, width = 0, height = 0, border_width = 0, override_redirect = 0}, xdestroywindow = {type = 74, serial = 0, send_event = 0, display = 0x0, event = 0, 
            window = 0}, xunmap = {type = 74, serial = 0, send_event = 0, display = 0x0, event = 0, window = 0, from_configure = 0}, xmap = {type = 74, serial = 0, send_event = 0, display = 0x0, event = 0, window = 0, 
            override_redirect = 0}, xmaprequest = {type = 74, serial = 0, send_event = 0, display = 0x0, parent = 0, window = 0}, xreparent = {type = 74, serial = 0, send_event = 0, display = 0x0, event = 0, window = 0, parent = 0, 
            x = 0, y = 0, override_redirect = 0}, xconfigure = {type = 74, serial = 0, send_event = 0, display = 0x0, event = 0, window = 0, x = 0, y = 0, width = 0, height = 0, border_width = 0, above = 0, override_redirect = 0}, 
          xgravity = {type = 74, serial = 0, send_event = 0, display = 0x0, event = 0, window = 0, x = 0, y = 0}, xresizerequest = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, width = 0, height = 0}, 
          xconfigurerequest = {type = 74, serial = 0, send_event = 0, display = 0x0, parent = 0, window = 0, x = 0, y = 0, width = 0, height = 0, border_width = 0, above = 0, detail = 0, value_mask = 0}, xcirculate = {type = 74, 
            serial = 0, send_event = 0, display = 0x0, event = 0, window = 0, place = 0}, xcirculaterequest = {type = 74, serial = 0, send_event = 0, display = 0x0, parent = 0, window = 0, place = 0}, xproperty = {type = 74, 
            serial = 0, send_event = 0, display = 0x0, window = 0, atom = 0, time = 0, state = 0}, xselectionclear = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, selection = 0, time = 0}, xselectionrequest = {
            type = 74, serial = 0, send_event = 0, display = 0x0, owner = 0, requestor = 0, selection = 0, target = 0, property = 0, time = 0}, xselection = {type = 74, serial = 0, send_event = 0, display = 0x0, requestor = 0, 
            selection = 0, target = 0, property = 0, time = 0}, xcolormap = {type = 74, serial = 0, send_event = 0, display = 0x0, window = 0, colormap = 0, c_new = 0, state = 0}, xclient = {type = 74, serial = 0, send_event = 0, 
            display = 0x0, window = 0, message_type = 0, format = 0, data = {b = '\000' <repeats 19 times>, s = {0, 0, 0, 0, 0, 0, 0, 0, 0, 0}, l = {0, 0, 0, 0, 0}}}, xmapping = {type = 74, serial = 0, send_event = 0, display = 0x0, 
            window = 0, request = 0, first_keycode = 0, count = 0}, xerror = {type = 74, display = 0x0, resourceid = 0, serial = 0, error_code = 0 '\000', request_code = 0 '\000', minor_code = 0 '\000'}, xkeymap = {type = 74, 
            serial = 0, send_event = 0, display = 0x0, window = 0, key_vector = '\000' <repeats 31 times>}, xgeneric = {type = 74, serial = 0, send_event = 0, display = 0x0, extension = 0, evtype = 0}, xcookie = {type = 74, serial = 0, 
            send_event = 0, display = 0x0, extension = 0, evtype = 0, cookie = 0, data = 0x0}, pad = {74, 0 <repeats 23 times>}}
        source = 0x21150
        marker = 436
#3  0xb627e008 in g_main_dispatch (context=0x20538) at /build/buildd/glib2.0-2.32.3/./glib/gmain.c:2539
        dispatch = 0xb6a450c5 <x11EventSourceDispatch(GSource*, GSourceFunc, gpointer)>
        was_in_call = 0
        user_data = 0x0
        callback = 0
        cb_funcs = 0x0
        cb_data = 0x0
        current_source_link = {data = 0x21150, next = 0x0}
        need_destroy = <optimized out>
        source = 0x21150
        current = 0x20330
        i = <optimized out>
#4  g_main_context_dispatch (context=0x20538) at /build/buildd/glib2.0-2.32.3/./glib/gmain.c:3075
No locals.
#5  0xb627e258 in g_main_context_iterate (dispatch=1, block=<optimized out>, context=0x20538, self=<optimized out>) at /build/buildd/glib2.0-2.32.3/./glib/gmain.c:3146
        timeout = 0
        some_ready = 1
        fds = 0x83390
        max_priority = 0
        nfds = 3
        allocated_nfds = <optimized out>
#6  g_main_context_iterate (context=0x20538, block=<optimized out>, dispatch=1, self=<optimized out>) at /build/buildd/glib2.0-2.32.3/./glib/gmain.c:3083
        some_ready = 1
#7  0xb627e2cc in g_main_context_iteration (context=0x20538, may_block=1) at /build/buildd/glib2.0-2.32.3/./glib/gmain.c:3207
        retval = <optimized out>
#8  0xb67c77b6 in QEventDispatcherGlib::processEvents (this=0x1f3d0, flags=...) at kernel/qeventdispatcher_glib.cpp:424
        d = 0x1f3e0
        savedFlags = {i = 0}
        result = <optimized out>
#9  0xb6a44f8c in QGuiEventDispatcherGlib::processEvents (this=<optimized out>, flags=...) at kernel/qguieventdispatcher_glib.cpp:204
        d = 0x1f3e0
        saved_flags = {i = 0}
        returnValue = false
#10 0xb67a6970 in QEventLoop::processEvents (this=<optimized out>, flags=...) at kernel/qeventloop.cpp:149
        d = 0x91830
#11 0xb67a6aee in QEventLoop::exec (this=0xbefff56c, flags=...) at kernel/qeventloop.cpp:204
        d = 0x91830
        locker = {val = 113700}
        app = 0xbefff5a8
#12 0xb67aa282 in QCoreApplication::exec () at kernel/qcoreapplication.cpp:1148
        threadData = 0x1bb88
        eventLoop = {<QObject> = {_vptr.QObject = 0xb689f718, static staticMetaObject = {d = {superdata = 0x0, stringdata = 0xb685d284 "QObject", data = 0xb685d358, extradata = 0xb689e424}}, static staticMetaObjectExtraData = {
              objects = 0x0, static_metacall = 0xb67b779d <QObject::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}, d_ptr = {d = 0x91830}, static staticQtMetaObject = {d = {superdata = 0x0, stringdata = 0xb6864308 "Qt", 
                data = 0xb6867c0c, extradata = 0x0}}}, static staticMetaObject = {d = {superdata = 0xb689e414, stringdata = 0xb686d96c "QEventLoop", data = 0xb686d990, extradata = 0xb689f758}}, static staticMetaObjectExtraData = {
            objects = 0x0, static_metacall = 0xb67e8879 <QEventLoop::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}}
        returnCode = <optimized out>
#13 0x0000ca6e in main (argc=1, argv=0xbefff704) at main.cpp:51
        a = {<QCoreApplication> = {<QObject> = {_vptr.QObject = 0xb6f49290, static staticMetaObject = {d = {superdata = 0x0, stringdata = 0xb685d284 "QObject", data = 0xb685d358, extradata = 0xb689e424}}, 
              static staticMetaObjectExtraData = {objects = 0x0, static_metacall = 0xb67b779d <QObject::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}, d_ptr = {d = 0x1ba88}, static staticQtMetaObject = {d = {
                  superdata = 0x0, stringdata = 0xb6864308 "Qt", data = 0xb6867c0c, extradata = 0x0}}}, static staticMetaObject = {d = {superdata = 0xb689e414, stringdata = 0xb686d9e0 "QCoreApplication", data = 0xb686da7c, 
                extradata = 0xb689f7c0}}, static staticMetaObjectExtraData = {objects = 0x0, static_metacall = 0xb67e8915 <QCoreApplication::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}, static self = 0x0}, 
          static staticMetaObject = {d = {superdata = 0xb689f7b0, stringdata = 0xb6e06c00 "QApplication", data = 0xb6e06e50, extradata = 0xb6f49300}}, static staticMetaObjectExtraData = {objects = 0x0, 
            static_metacall = 0xb69dd45d <QApplication::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}}
        mw = {<QMainWindow> = {<QWidget> = {<QObject> = {_vptr.QObject = 0xfa30, static staticMetaObject = {d = {superdata = 0x0, stringdata = 0xb685d284 "QObject", data = 0xb685d358, extradata = 0xb689e424}}, 
                static staticMetaObjectExtraData = {objects = 0x0, static_metacall = 0xb67b779d <QObject::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}, d_ptr = {d = 0x5b808}, static staticQtMetaObject = {d = {
                    superdata = 0x0, stringdata = 0xb6864308 "Qt", data = 0xb6867c0c, extradata = 0x0}}}, <QPaintDevice> = {_vptr.QPaintDevice = 0xfb14, painters = 0}, static staticMetaObject = {d = {superdata = 0xb689e414, 
                  stringdata = 0xb6e09ed0 "QWidget", data = 0xb6e0a478, extradata = 0xb6f4a1e0}}, static staticMetaObjectExtraData = {objects = 0x0, 
                static_metacall = 0xb6a0e3d9 <QWidget::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}, data = 0x5b8bc}, static staticMetaObject = {d = {superdata = 0xb6f4a1d0, stringdata = 0xb6e57c5c "QMainWindow", 
                data = 0xb6e57e00, extradata = 0xb6f5d780}}, static staticMetaObjectExtraData = {objects = 0xb6f64d8c, static_metacall = 0xb6e01975 <QMainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}}, 
          static staticMetaObject = {d = {superdata = 0x1a3b8, stringdata = 0xfb28 "MainWindow", data = 0xfb58, extradata = 0xfb50}}, static staticMetaObjectExtraData = {objects = 0x0, 
            static_metacall = 0xec99 <MainWindow::qt_static_metacall(QObject*, QMetaObject::Call, int, void**)>}}