$ gdb --args qmlplugindump-qt5 -nonrelocatable org.kde.kcm 1.1 .
GNU gdb (GDB) Fedora 8.1-15.fc28
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Reading symbols from qmlplugindump-qt5...Missing separate debuginfo for /usr/bin/qmlplugindump-qt5
Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/ad/1895ae52ad42bb680d89db57721b197bd918a2.debug
Reading symbols from /home/jmlich/workspace/qmlplugindump-qt5...(no debugging symbols found)...done.
(no debugging symbols found)...done.
(gdb) r
Starting program: /usr/bin/qmlplugindump-qt5 -nonrelocatable org.kde.kcm 1.1 .
Missing separate debuginfos, use: dnf debuginfo-install glibc-2.27-15.fc28.x86_64
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
[New Thread 0x7fffe179a700 (LWP 16224)]
Detaching after fork from child process 16225.
Found a dependency on QtQuick.Controls with two major versions:1.0 and 2.0 which is unsupported, discarding smaller version
Found a dependency on QtQuick.Controls with two major versions:1.0 and 2.1 which is unsupported, discarding smaller version
Found a dependency on QtQuick.Controls with two major versions:1.0 and 2.2 which is unsupported, discarding smaller version
Found a dependency on QtQuick.Controls with two major versions:1.0 and 2.3 which is unsupported, discarding smaller version
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QGuiApplication(0x55555558cdb0), parent's thread is QThread(0x55555558ce50), current thread is QThread(0x555555591da0)
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QGuiApplication(0x55555558cdb0), parent's thread is QThread(0x55555558ce50), current thread is QThread(0x555555591da0)
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QGuiApplication(0x55555558cdb0), parent's thread is QThread(0x55555558ce50), current thread is QThread(0x555555591da0)
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QGuiApplication(0x55555558cdb0), parent's thread is QThread(0x55555558ce50), current thread is QThread(0x555555591da0)
QObject::installEventFilter(): Cannot filter events for objects in a different thread.
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QGuiApplication(0x55555558cdb0), parent's thread is QThread(0x55555558ce50), current thread is QThread(0x555555591da0)
Missing separate debuginfo for /lib64/libEGL.so.1
Try: dnf --enablerepo='*debug*' install /usr/lib/debug/.build-id/a5/e2b8a11abf824e67560c8e119a031b079c92e1.debug
Could not find any platform plugin
[New Thread 0x7fffd1842700 (LWP 16226)]
Unknown property type for key "X-Plasma-API" -> falling back to string
QObject: Cannot create children for a parent that is in a different thread.
(Parent is QGuiApplication(0x55555558cdb0), parent's thread is QThread(0x55555558ce50), current thread is QThread(0x555555591da0)
QObject::installEventFilter(): Cannot filter events for objects in a different thread.

Thread 1 "qmlplugindump-q" received signal SIGSEGV, Segmentation fault.
QtQuickPrivate::cancelDeferred(QObject*, int) () at qquickdeferredexecute.cpp:61
61	    auto dit = ddata->deferredData.rbegin();
(gdb) bt full thread
#0  QtQuickPrivate::cancelDeferred(QObject*, int) () at qquickdeferredexecute.cpp:61
        ddata = 0x0
        dit = <optimized out>
#1  0x00007fffe0452bb0 in QtQuickPrivate::cancelDeferred (object=0x55555568ebc0, property=...) at qquickdeferredexecute.cpp:131
No locals.
#2  0x00007fffe0470702 in quickCancelDeferred (property=..., object=<optimized out>) at qquickdeferredexecute_p_p.h:75
No locals.
#3  QQuickPopupItemPrivate::cancelContentItem (this=<optimized out>) at qquickpopupitem.cpp:123
No locals.
#4  0x00007fffe044ef89 in QQuickControlPrivate::setContentItem_helper (this=this@entry=0x555555658f80, item=0x55555568f080, notify=notify@entry=false)
    at qquickcontrol.cpp:294
        q = <optimized out>
#5  0x00007fffe0450acf in QQuickControl::contentItem (this=<optimized out>) at qquickcontrol.cpp:1356
        d = <optimized out>
#6  0x00007fffe046eda4 in QQuickPopup::contentItem (this=<optimized out>) at qquickpopup.cpp:1636
        d = <optimized out>
#7  0x00007fffe04a320f in QQuickPopup::qt_static_metacall (_o=_o@entry=0x55555568ebc0, _c=_c@entry=QMetaObject::ReadProperty, _id=_id@entry=25,
    _a=_a@entry=0x7fffffffcf60) at .moc/moc_qquickpopup_p.cpp:1007
        _t = 0x55555568ebc0
        _v = 0x7fffffffcf20
#8  0x00007fffe04a3cdb in QQuickPopup::qt_metacall (this=this@entry=0x55555568ebc0, _c=_c@entry=QMetaObject::ReadProperty, _id=25,
    _a=_a@entry=0x7fffffffcf60) at .moc/moc_qquickpopup_p.cpp:1143
No locals.
#9  0x00007fffe049daa9 in QQuickDrawer::qt_metacall (this=0x55555568ebc0, _c=QMetaObject::ReadProperty, _id=<optimized out>, _a=0x7fffffffcf60)
    at .moc/moc_qquickdrawer_p.cpp:205
No locals.
#10 0x00007ffff672b18a in QMetaProperty::read(QObject const*) const () at kernel/qmetaobject.cpp:3128
        t = 1194
        status = -1
        value = {d = {data = {c = 0 '\000', uc = 0 '\000', s = 0, sc = 0 '\000', us = 0, i = 0, u = 0, l = 0, ul = 0, b = false, d = 0, f = 0, real = 0,
              ll = 0, ull = 0, o = 0x0, ptr = 0x0, shared = 0x0}, type = 1194, is_shared = 0, is_null = 0}}
        argv = {0x7fffffffcf20, 0x7fffffffcf20, 0x7fffffffcf1c}
#11 0x000055555555fd6c in collectReachableMetaObjects(QObject*, QSet<QMetaObject const*>*) [clone .localalias.265] ()
No symbol table info available.
#12 0x0000555555561274 in collectReachableMetaObjects(QQmlEngine*, QSet<QMetaObject const*>&, QSet<QMetaObject const*>&, QList<QQmlType> const&) ()
No symbol table info available.
#13 0x000055555555c96d in main ()
No symbol table info available.