.
Thread 8 (LWP 17837):
#0  0x00007f481a5a9ddd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f48197e4fe4 in ?? ()
No symbol table info available.
#2  0x00007f481aea5990 in ?? () from /tmp/apport_sandbox_xwXXY6/usr/lib/x86_64-linux-gnu/libQt5Core.so.5
No symbol table info available.
#3  0x00000001197a8478 in ?? ()
No symbol table info available.
#4  0x00007f47e8000990 in ?? ()
No symbol table info available.
#5  0xffffffff7fffffff in ?? ()
No symbol table info available.
#6  0x0000000000000024 in ?? ()
No symbol table info available.
#7  0x00007f47e8000990 in ?? ()
No symbol table info available.
#8  0x0000000000000001 in ?? ()
No symbol table info available.
#9  0x0000000000000024 in ?? ()
No symbol table info available.
#10 0x00007f47e80008c0 in ?? ()
No symbol table info available.
#11 0x0000000000000000 in ?? ()
No symbol table info available.
.
Thread 7 (LWP 17833):
#0  0x00007f481a5a9ddd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f48197e4fe4 in ?? ()
No symbol table info available.
#2  0x0000000000000000 in ?? ()
No symbol table info available.
.
Thread 6 (LWP 17835):
#0  pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
No locals.
#1  0x00007f4819826cf5 in ?? ()
No symbol table info available.
#2  0x000000000000328b in ?? ()
No symbol table info available.
#3  0x00000000275cc840 in ?? ()
No symbol table info available.
#4  0x00000000010551a0 in ?? ()
No symbol table info available.
#5  0x00000000010ee898 in ?? ()
No symbol table info available.
#6  0x00000000010ee880 in ?? ()
No symbol table info available.
#7  0x00007f48197bb1c1 in ?? ()
No symbol table info available.
#8  0x00000000010eef40 in ?? ()
No symbol table info available.
#9  0x00000000010551a0 in ?? ()
No symbol table info available.
#10 0x0000000000000000 in ?? ()
No symbol table info available.
.
Thread 5 (LWP 17830):
#0  0x00007f481a5a9ddd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f48169aeb72 in poll (__timeout=-1, __nfds=1, __fds=0x7f4810803d40) at /usr/include/x86_64-linux-gnu/bits/poll2.h:46
No locals.
#2  _xcb_conn_wait (c=c@entry=0xf39dd0, cond=cond@entry=0xf39e10, vector=vector@entry=0x0, count=count@entry=0x0) at ../../src/xcb_conn.c:447
        ret = <optimized out>
        fd = {fd = 3, events = 1, revents = 0}
#3  0x00007f48169b064f in xcb_wait_for_event (c=0xf39dd0) at ../../src/xcb_in.c:622
        ret = 0x0
#4  0x00007f48132524c9 in QXcbEventReader::run (this=0xf43d90) at qxcbconnection.cpp:1023
        event = <optimized out>
#5  0x00007f481af1f233 in QThreadPrivate::start (arg=0xf43d90) at thread/qthread_unix.cpp:345
        __clframe = {__cancel_routine = 0x7f481af1e500 <QThreadPrivate::finish(void*)>, __cancel_arg = 0xf43d90, __do_it = 1, __cancel_type = <optimized out>}
        thr = 0xf43d90
        data = <optimized out>
        objectName = {static null = {<No data fields>}, d = 0x7f481b18d660 <QArrayData::shared_null>}
#6  0x00007f4819cfd182 in start_thread (arg=0x7f4810804700) at pthread_create.c:312
        __res = <optimized out>
        pd = 0x7f4810804700
        now = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {139947491215104, 3073221250503886230, 0, 0, 139947491215808, 139947491215104, -3155220751117236842, -3155204821801417322}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x0, 0x0}, data = {prev = 0x0, cleanup = 0x0, canceltype = 0}}}
        not_first_call = <optimized out>
        pagesize_m1 = <optimized out>
        sp = <optimized out>
        freesize = <optimized out>
        __PRETTY_FUNCTION__ = "start_thread"
#7  0x00007f481a5b712d in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:111
No locals.
.
Thread 4 (LWP 17834):
#0  pthread_cond_timedwait@@GLIBC_2.3.2 () at ../nptl/sysdeps/unix/sysv/linux/x86_64/pthread_cond_timedwait.S:238
No locals.
#1  0x00007f4819826cf5 in ?? ()
No symbol table info available.
#2  0x000000000000328b in ?? ()
No symbol table info available.
#3  0x00000000312f9d20 in ?? ()
No symbol table info available.
#4  0x00000000010fdb90 in ?? ()
No symbol table info available.
#5  0x00000000010ee898 in ?? ()
No symbol table info available.
#6  0x00000000010ee880 in ?? ()
No symbol table info available.
#7  0x00007f48197bb1c1 in ?? ()
No symbol table info available.
#8  0x00000000010eef40 in ?? ()
No symbol table info available.
#9  0x00000000010fdb90 in ?? ()
No symbol table info available.
#10 0x0000000000000000 in ?? ()
No symbol table info available.
.
Thread 3 (LWP 17832):
#0  0x00007f481a5a9ddd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f48197e4fe4 in ?? ()
No symbol table info available.
#2  0x0000000000000000 in ?? ()
No symbol table info available.
.
Thread 2 (LWP 17831):
#0  0x00007f481a5a9ddd in poll () at ../sysdeps/unix/syscall-template.S:81
No locals.
#1  0x00007f48197e4fe4 in ?? ()
No symbol table info available.
#2  0x0000000000000000 in ?? ()
No symbol table info available.
.
Thread 1 (LWP 17829):
#0  mark (engine=0x1157820, this=<optimized out>) at jsruntime/qv4engine_p.h:373
No locals.
#1  mark (e=0x1157820, this=0x1457cd0) at jsruntime/qv4value_p.h:93
No locals.
#2  QV4::Object::markObjects (that=0x7f47f0fe0480, e=0x1157820) at jsruntime/qv4object.cpp:263
        i = 2
        o = 0x7f47f0fe0480
#3  0x00007f481c515c36 in QV4::MemoryManager::mark (this=this@entry=0x1152810) at jsruntime/qv4mm.cpp:433
        markBase = 0x7f47f28000d0
        persistent = <optimized out>
#4  0x00007f481c5162c7 in QV4::MemoryManager::runGC (this=0x1152810) at jsruntime/qv4mm.cpp:564
        this = 0x1152810
#5  0x00007f481c5164b6 in QV4::MemoryManager::alloc (this=0x1152810, size=48) at jsruntime/qv4mm.cpp:294
        pos = 3
        m = <optimized out>
#6  0x00007f481c4fe177 in QV4::ExecutionEngine::newString (this=0x1157820, s=...) at jsruntime/qv4engine.cpp:476
No locals.
#7  0x00007f481c5069e3 in QV4::__qmljs_string_from_number (ctx=0x7fff21135df0, number=<optimized out>) at jsruntime/qv4runtime.cpp:370
        qstr = {static null = {<No data fields>}, d = 0x1386030}
#8  0x00007f481c50c8f1 in QV4::Value::toString (this=<optimized out>, ctx=<optimized out>) at jsruntime/qv4value.cpp:269
No locals.
#9  0x00007f481c50a0b7 in QV4::__qmljs_call_element (context=0x7fff21135df0, index=..., callData=...) at jsruntime/qv4runtime.cpp:933
        baseObject = {ptr = 0x7f47f28000c8}
        s = <optimized out>
#10 0x00007f47f1028987 in ?? ()
No symbol table info available.
#11 0x00007fff21135de0 in ?? ()
No symbol table info available.
#12 0x0001000000000001 in ?? ()
No symbol table info available.
#13 0x0000005b1c518a90 in ?? ()
No symbol table info available.
#14 0x0000000000000000 in ?? ()
No symbol table info available.