UI Fails to start - 5.2.12 - qtcore 5.9.4

[Lyall Pearce]

Linux 64 bit, intel Core i77-7700, Gentoo Linux kernel 4.9.95-gentoo

Virtualbox 5.2.12 built from source using Gentoo portage.

QTcore 5.9.4 built from source using Gentoo portage.

There is no qt4 on the system, only qt5.

Tried downgrading to VirtualBox 5.1.36

Don't have any Gentoo standard options to downgrade qtcore short of unmasking qt4

Built with gcc 6.4.0

Happy to build with debug, including qtcore, or supply any info that may assist with this.

$ VirtualBox 
Qt FATAL: ASSERT failure in QCoreApplication::sendEvent: "Cannot send events to objects owned by a different thread. Current thread 0x0x5653f2bae6d0. Receivr '' (of type 'UITaskMediumEnumeration') was created in thread 0x0x5653f2877050", file kernel/qcoreapplication.cpp, line 563
Aborted

[Lyall Pearce]

Stack trace from core.

# gdb /usr/lib64/virtualbox/VirtualBox /data/cores/core.UIThreadWorker.30097.0.6.1526289981 
GNU gdb (Gentoo 7.12.1 vanilla) 7.12.1
Copyright (C) 2017 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.  Type "show copying"
and "show warranty" for details.
This GDB was configured as "x86_64-pc-linux-gnu".
Type "show configuration" for configuration details.
For bug reporting instructions, please see:
<https://bugs.gentoo.org/>.
Find the GDB manual and other documentation resources online at:
<http://www.gnu.org/software/gdb/documentation/>.
For help, type "help".
Type "apropos word" to search for commands related to "word"...
Reading symbols from /usr/lib64/virtualbox/VirtualBox...Reading symbols from /usr/lib64/debug//usr/lib64/virtualbox/VirtualBox.debug...done.
done.
[New LWP 30137]
[New LWP 30119]
[New LWP 30110]
[New LWP 30118]
[New LWP 30112]
[New LWP 30133]
[New LWP 30134]
[New LWP 30136]
[New LWP 30097]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Core was generated by `/usr/lib64/virtualbox/VirtualBox'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00007f12a5318f90 in raise () from /lib64/libc.so.6
[Current thread is 1 (Thread 0x7f12764da700 (LWP 30137))]
(gdb) where
#0  0x00007f12a5318f90 in raise () from /lib64/libc.so.6
#1  0x00007f12a531ac5a in abort () from /lib64/libc.so.6
#2  0x00007f1299912a7f in qt_message_fatal (context=..., message=<synthetic pointer>...) at global/qlogging.cpp:1690
#3  QMessageLogger::fatal (this=this@entry=0x7f12764d9730, msg=msg@entry=0x7f1299b92d28 "ASSERT failure in %s: \"%s\", file %s, line %d")
    at global/qlogging.cpp:796
#4  0x00007f129990d72a in qt_assert_x (where=where@entry=0x7f1299c583b9 "QCoreApplication::sendEvent", what=<optimized out>, 
    file=file@entry=0x7f1299c58364 "kernel/qcoreapplication.cpp", line=line@entry=563) at global/qglobal.cpp:3088
#5  0x00007f1299ae8be9 in QCoreApplicationPrivate::checkReceiverThread (receiver=<optimized out>) at kernel/qcoreapplication.cpp:557
#6  0x00007f1298a32cc7 in QApplication::notify(QObject*, QEvent*) () from /usr/lib64/libQt5Widgets.so.5
#7  0x00007f1299ae92ba in QCoreApplication::notifyInternal2 (receiver=receiver@entry=0x56344e96d6d0, event=event@entry=0x7f12764d99f0)
    at kernel/qcoreapplication.cpp:1016
#8  0x00007f1299b2008e in QCoreApplication::sendEvent (event=0x7f12764d99f0, receiver=0x56344e96d6d0) at kernel/qcoreapplication.h:233
#9  QObject::setProperty (this=this@entry=0x56344e96d6d0, name=name@entry=0x7f129b7e2756 "medium", value=...) at kernel/qobject.cpp:3903
#10 0x00007f129b484953 in UITaskMediumEnumeration::run (this=0x56344e96d6d0)
    at /tmp/portage/app-emulation/virtualbox-5.2.12/work/VirtualBox-5.2.12/src/VBox/Frontends/VirtualBox/src/medium/UIMediumEnumerator.cpp:65
#11 0x00007f129b44539a in UITask::start (this=0x56344e96d6d0)
    at /tmp/portage/app-emulation/virtualbox-5.2.12/work/VirtualBox-5.2.12/src/VBox/Frontends/VirtualBox/src/globals/UIThreadPool.cpp:298
#12 UIThreadWorker::run (this=0x56344e986bc0)
    at /tmp/portage/app-emulation/virtualbox-5.2.12/work/VirtualBox-5.2.12/src/VBox/Frontends/VirtualBox/src/globals/UIThreadPool.cpp:322
#13 0x00007f1299929212 in QThreadPrivate::start (arg=0x56344e986bc0) at thread/qthread_unix.cpp:368
#14 0x00007f12a589e8e7 in start_thread () from /lib64/libpthread.so.0
#15 0x00007f12a53dd09f in clone () from /lib64/libc.so.6
(gdb) 

[Socratis]

Related discussion in the forums: ​https://forums.virtualbox.org/viewtopic.php?f=10&t=87940

[Lyall Pearce]

I can still use VBoxManage to start/stop VM's in headless but have to use ssh/rdesktop to access them. If I attempt to start the VM's with a UI, the UI crashes, as above.