Fix T86170: Memory leak clearing the Python instance for COW id data

As Python can access COW ID's, ensure it's instance is kept on update.

This could happen when the "Use Self" argument was enabled for a driver.

2 files changed, 10 insertions, 0 deletions

diff --git a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc
index 7a0c1b5b693..0064240db23 100644
--- a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc
+++ b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.cc
@@ -33,6 +33,7 @@ namespace blender::deg {
 
 RuntimeBackup::RuntimeBackup(const Depsgraph *depsgraph)
     : have_backup(false),
+      id_data({.py_instance = nullptr}),
       animation_backup(depsgraph),
       scene_backup(depsgraph),
       sound_backup(depsgraph),
@@ -51,6 +52,8 @@ void RuntimeBackup::init_from_id(ID *id)
   }
   have_backup = true;
 
+  id_data.py_instance = id->py_instance;
+
   animation_backup.init_from_id(id);
 
   const ID_Type id_type = GS(id->name);
@@ -89,6 +92,8 @@ void RuntimeBackup::restore_to_id(ID *id)
     return;
   }
 
+  id->py_instance = id_data.py_instance;
+
   animation_backup.restore_to_id(id);
 
   const ID_Type id_type = GS(id->name);
diff --git a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h
index c6249c83daa..0629dbe62b4 100644
--- a/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h
+++ b/source/blender/depsgraph/intern/eval/deg_eval_runtime_backup.h
@@ -58,6 +58,11 @@ class RuntimeBackup {
    * copy-on-write mechanism. */
   bool have_backup;
 
+  /* Struct members of the ID pointer. */
+  struct {
+    void *py_instance;
+  } id_data;
+
   AnimationBackup animation_backup;
   SceneBackup scene_backup;
   SoundBackup sound_backup;