1 files changed, 50 insertions, 6 deletions

diff --git a/scene/3d/physics_joint_3d.cpp b/scene/3d/physics_joint_3d.cpp
index 06de5ad0ae..0a2af6b0cd 100644
--- a/scene/3d/physics_joint_3d.cpp
+++ b/scene/3d/physics_joint_3d.cpp
@@ -5,8 +5,8 @@
 /*                           GODOT ENGINE                                */
 /*                      https://godotengine.org                          */
 /*************************************************************************/
-/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
-/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
+/* Copyright (c) 2007-2021 Juan Linietsky, Ariel Manzur.                 */
+/* Copyright (c) 2014-2021 Godot Engine contributors (cf. AUTHORS.md).   */
 /*                                                                       */
 /* Permission is hereby granted, free of charge, to any person obtaining */
 /* a copy of this software and associated documentation files (the       */
@@ -30,6 +30,37 @@
 
 #include "physics_joint_3d.h"
 
+#include "scene/scene_string_names.h"
+
+void Joint3D::_disconnect_signals() {
+	Node *node_a = get_node_or_null(a);
+	PhysicsBody3D *body_a = Object::cast_to<PhysicsBody3D>(node_a);
+	if (body_a) {
+		body_a->disconnect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &Joint3D::_body_exit_tree));
+	}
+
+	Node *node_b = get_node_or_null(b);
+	PhysicsBody3D *body_b = Object::cast_to<PhysicsBody3D>(node_b);
+	if (body_b) {
+		body_b->disconnect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &Joint3D::_body_exit_tree));
+	}
+}
+
+void Joint3D::_body_exit_tree(const ObjectID &p_body_id) {
+	_disconnect_signals();
+	Object *object = ObjectDB::get_instance(p_body_id);
+	PhysicsBody3D *body = Object::cast_to<PhysicsBody3D>(object);
+	ERR_FAIL_NULL(body);
+	RID body_rid = body->get_rid();
+	if (ba == body_rid) {
+		a = NodePath();
+	}
+	if (bb == body_rid) {
+		b = NodePath();
+	}
+	_update_joint();
+}
+
 void Joint3D::_update_joint(bool p_only_free) {
 	if (joint.is_valid()) {
 		if (ba.is_valid() && bb.is_valid()) {
@@ -47,8 +78,8 @@ void Joint3D::_update_joint(bool p_only_free) {
 		return;
 	}
 
-	Node *node_a = has_node(get_node_a()) ? get_node(get_node_a()) : (Node *)nullptr;
-	Node *node_b = has_node(get_node_b()) ? get_node(get_node_b()) : (Node *)nullptr;
+	Node *node_a = get_node_or_null(a);
+	Node *node_b = get_node_or_null(b);
 
 	PhysicsBody3D *body_a = Object::cast_to<PhysicsBody3D>(node_a);
 	PhysicsBody3D *body_b = Object::cast_to<PhysicsBody3D>(node_b);
@@ -97,8 +128,11 @@ void Joint3D::_update_joint(bool p_only_free) {
 	PhysicsServer3D::get_singleton()->joint_set_solver_priority(joint, solver_priority);
 
 	ba = body_a->get_rid();
+	body_a->connect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &Joint3D::_body_exit_tree), make_binds(body_a->get_instance_id()));
+
 	if (body_b) {
 		bb = body_b->get_rid();
+		body_b->connect(SceneStringNames::get_singleton()->tree_exiting, callable_mp(this, &Joint3D::_body_exit_tree), make_binds(body_b->get_instance_id()));
 	}
 
 	PhysicsServer3D::get_singleton()->joint_disable_collisions_between_bodies(joint, exclude_from_collision);
@@ -109,6 +143,10 @@ void Joint3D::set_node_a(const NodePath &p_node_a) {
 		return;
 	}
 
+	if (joint.is_valid()) {
+		_disconnect_signals();
+	}
+
 	a = p_node_a;
 	_update_joint();
 }
@@ -121,6 +159,11 @@ void Joint3D::set_node_b(const NodePath &p_node_b) {
 	if (b == p_node_b) {
 		return;
 	}
+
+	if (joint.is_valid()) {
+		_disconnect_signals();
+	}
+
 	b = p_node_b;
 	_update_joint();
 }
@@ -147,6 +190,7 @@ void Joint3D::_notification(int p_what) {
 		} break;
 		case NOTIFICATION_EXIT_TREE: {
 			if (joint.is_valid()) {
+				_disconnect_signals();
 				_update_joint(true);
 			}
 		} break;
@@ -168,8 +212,8 @@ bool Joint3D::get_exclude_nodes_from_collision() const {
 String Joint3D::get_configuration_warning() const {
 	String node_warning = Node3D::get_configuration_warning();
 
-	if (!warning.empty()) {
-		if (!node_warning.empty()) {
+	if (!warning.is_empty()) {
+		if (!node_warning.is_empty()) {
 			node_warning += "\n\n";
 		}
 		node_warning += warning;