CDS supports loading archived classes into custom class loaders. (These classes are called "unregistered classes" in CDS terminology.)

In some cases, an "unregistered class" may fail to load but gets added to the ClassLoaderData of the custom class loader. This will cause an assert in debug builds:

# assert(ik->is_loaded()) failed: class should be loaded 0x000000000b518eb8
V [libjvm.so+0xfa6bd5] InstanceKlass::unload_class(InstanceKlass*)+0x555 (instanceKlass.cpp:2870)
V [libjvm.so+0xa790e3] ClassLoaderData::classes_do(void (*)(InstanceKlass*))+0xc3 (classLoaderData.cpp:441)
V [libjvm.so+0xa7d61e] ClassLoaderData::unload()+0x12e (classLoaderData.cpp:628)
V [libjvm.so+0xa908b4] ClassUnloadingContext::register_unloading_class_loader_data(ClassLoaderData*)+0x24 (classUnloadingContext.cpp:70)
V [libjvm.so+0xa863b4] ClassLoaderDataGraph::do_unloading()+0x84 (classLoaderDataGraph.cpp:423)
V [libjvm.so+0x198d832] SystemDictionary::do_unloading(GCTimer*)+0x172 (systemDictionary.cpp:1562)
V [libjvm.so+0xd9a80a] G1CollectedHeap::unload_classes_and_code(char const*, BoolObjectClosure*, GCTimer*)+0x1ba (g1CollectedHeap.cpp:2685)
V [libjvm.so+0xdee362] G1FullCollector::phase1_mark_live_objects()+0x6c2 (g1FullCollector.cpp:323)
V [libjvm.so+0xdee49c] G1FullCollector::collect()+0x1c (g1FullCollector.cpp:208)
V [libjvm.so+0xd94fd7] G1CollectedHeap::do_full_collection(bool, bool, unsigned long)+0x227 (g1CollectedHeap.cpp:895)
V [libjvm.so+0xeb7d9e] VM_G1CollectFull::doit()+0x4e (g1VMOperations.cpp:55)
V [libjvm.so+0x1ae3617] VM_Operation::evaluate()+0xf7 (vmOperations.cpp:74)
V [libjvm.so+0x1aff37b] VMThread::evaluate_operation(VM_Operation*)+0x6fb (vmThread.cpp:284)
V [libjvm.so+0x1affc13] VMThread::inner_execute(VM_Operation*)+0x393 (vmThread.cpp:421)
V [libjvm.so+0x1affdd4] VMThread::loop()+0x84 (vmThread.cpp:487)
V [libjvm.so+0x1affee2] VMThread::run()+0x92 (vmThread.cpp:177)
V [libjvm.so+0x19ee08a] Thread::call_run()+0xba (thread.cpp:243)
V [libjvm.so+0x1692583] thread_native_entry(Thread*)+0x123 (os_linux.cpp:896)
C [libc.so.6+0x9caa4]