Fix T37709: Memory corruption when freeing custom bone shape objects

Summary:
Issue was caused by access to pchan->custom object from channel free
function when freeing all objects from main. Order of objects free
is not defined and such an access might easily end up with access
to freed memory.

We don't need to do user counter stuff when freeing main, so added
an _ex functions with do_id_user flag which is used when freeing main.

We had the same issue with other datablocks, so now it should be
easier to support relevant user counter.

This issue was caused by the fix for T36391, so perhaps that's indeed
high time to do real user counter.

Reviewers: brecht, campbellbarton

Reviewed By: campbellbarton

Maniphest Tasks: T37709

Differential Revision: https://developer.blender.org/D137

1 files changed, 1 insertions, 0 deletions

diff --git a/source/blender/blenkernel/BKE_object.h b/source/blender/blenkernel/BKE_object.h
index e6e6d621ef3..94995404f2b 100644
--- a/source/blender/blenkernel/BKE_object.h
+++ b/source/blender/blenkernel/BKE_object.h
@@ -65,6 +65,7 @@ void BKE_object_free_curve_cache(struct Object *ob);
 void BKE_object_update_base_layer(struct Scene *scene, struct Object *ob);
 
 void BKE_object_free(struct Object *ob);
+void BKE_object_free_ex(struct Object *ob, bool do_id_user);
 void BKE_object_free_derived_caches(struct Object *ob);
 
 void BKE_object_modifier_hook_reset(struct Object *ob, struct HookModifierData *hmd);