Fix T55244: Parenting object(s) to curve crashes blender

There is a chance parts of Blender call BKE_object_workob_calc_parent
with ob->parent objects that are outside the depsgraph.

This we can tackle later since these are corner cases anyways,
and this fix fixes all parenting operators in Blender.

1 files changed, 20 insertions, 11 deletions

diff --git a/source/blender/blenkernel/intern/object.c b/source/blender/blenkernel/intern/object.c
index 57324b88912..1b6916a2d55 100644
--- a/source/blender/blenkernel/intern/object.c
+++ b/source/blender/blenkernel/intern/object.c
@@ -2168,28 +2168,37 @@ void BKE_object_where_is_calc(Depsgraph *depsgraph, Scene *scene, Object *ob)
 	BKE_object_where_is_calc_time_ex(depsgraph, scene, ob, BKE_scene_frame_get(scene), NULL, NULL);
 }
 
-/* for calculation of the inverse parent transform, only used for editor */
+/**
+ * For calculation of the inverse parent transform, only used for editor.
+ *
+ * It assumes the object parent is already in the depsgraph.
+ * Otherwise, after changing ob->parent you need to call:
+ *  DEG_relations_tag_update(bmain);
+ *  BKE_scene_graph_update_tagged(depsgraph, bmain);
+ */
 void BKE_object_workob_calc_parent(Depsgraph *depsgraph, Scene *scene, Object *ob, Object *workob)
 {
+	Object *ob_eval = DEG_get_evaluated_object(depsgraph, ob);
 	BKE_object_workob_clear(workob);
 	
 	unit_m4(workob->obmat);
 	unit_m4(workob->parentinv);
 	unit_m4(workob->constinv);
-	workob->parent = ob->parent;
 
-	workob->trackflag = ob->trackflag;
-	workob->upflag = ob->upflag;
+	/* Since this is used while calculating parenting, at this moment ob_eval->parent is still NULL. */
+	workob->parent = DEG_get_evaluated_object(depsgraph, ob->parent);
+
+	workob->trackflag = ob_eval->trackflag;
+	workob->upflag = ob_eval->upflag;
 	
-	workob->partype = ob->partype;
-	workob->par1 = ob->par1;
-	workob->par2 = ob->par2;
-	workob->par3 = ob->par3;
+	workob->partype = ob_eval->partype;
+	workob->par1 = ob_eval->par1;
+	workob->par2 = ob_eval->par2;
+	workob->par3 = ob_eval->par3;
 
-	workob->constraints.first = ob->constraints.first;
-	workob->constraints.last = ob->constraints.last;
+	workob->constraints = ob_eval->constraints;
 
-	BLI_strncpy(workob->parsubstr, ob->parsubstr, sizeof(workob->parsubstr));
+	BLI_strncpy(workob->parsubstr, ob_eval->parsubstr, sizeof(workob->parsubstr));
 
 	BKE_object_where_is_calc(depsgraph, scene, workob);
 }