8308764: Reporting errors from create_vm may crash

Reviewed-by: stuefe, coleenp, kbarrett

src/hotspot/share/prims/jni.cpp

@@ -3628,8 +3628,10 @@ static jint JNI_CreateJavaVM_inner(JavaVM **vm, void **penv, void *args) {
     // to continue.
     if (Universe::is_fully_initialized()) {
       // otherwise no pending exception possible - VM will already have aborted
-      JavaThread* THREAD = JavaThread::current(); // For exception macros.
-      if (HAS_PENDING_EXCEPTION) {
+      Thread* current = Thread::current_or_null();
+      if (current != nullptr) {
+        JavaThread* THREAD = JavaThread::cast(current); // For exception macros.
+        assert(HAS_PENDING_EXCEPTION, "must be - else no current thread exists");
         HandleMark hm(THREAD);
         vm_exit_during_initialization(Handle(THREAD, PENDING_EXCEPTION));
       }

src/hotspot/share/runtime/threads.cpp

@@ -564,7 +564,12 @@ jint Threads::create_vm(JavaVMInitArgs* args, bool* canTryAgain) {
   status = init_globals2();
   if (status != JNI_OK) {
     Threads::remove(main_thread, false);
-    main_thread->smr_delete();
+    // It is possible that we managed to fully initialize Universe but have then
+    // failed by throwing an exception. In that case our caller JNI_CreateJavaVM
+    // will want to report it, so we can't delete the main thread.
+    if (!main_thread->has_pending_exception()) {
+      main_thread->smr_delete();
+    }
     *canTryAgain = false; // don't let caller call JNI_CreateJavaVM again
     return status;
   }