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_library.h b/source/blender/blenkernel/BKE_library.h
index b8da5002d84..f97bb911a12 100644
--- a/source/blender/blenkernel/BKE_library.h
+++ b/source/blender/blenkernel/BKE_library.h
@@ -74,6 +74,7 @@ struct ListBase *which_libbase(struct Main *mainlib, short type);
 int set_listbasepointers(struct Main *main, struct ListBase **lb);
 
 void BKE_libblock_free(struct ListBase *lb, void *idv);
+void BKE_libblock_free_ex(struct ListBase *lb, void *idv, bool do_id_user);
 void BKE_libblock_free_us(struct ListBase *lb, void *idv);
 void BKE_libblock_free_data(struct ID *id);
 void free_main(struct Main *mainvar);