Fix (unreported) crash when undoing after ID deletion.

Yes, we do can undo an ID deletion now.

However, this requires extra care in UI 'remapping' to new IDs step
(when undoing, we do not fully reload the UI from saved .blend).
Otherwise, new UI (i.e. one from saved .blend file) might reference
IDs that where freed in old bmain (the one before the undo), we cannot
use those to get ID name then, that would be a nasty use-after-free!

To prevent this, we generate a GSet of all valid ID pointers at that
time (i.e. those found in both old and new Main's), and ensure any ID
we try to remap by its name is in that GSet. Otherwise, there is no
possible remapping, just return NULL.

1 files changed, 4 insertions, 2 deletions

diff --git a/source/blender/blenkernel/BKE_library_idmap.h b/source/blender/blenkernel/BKE_library_idmap.h
index ec814ac73de..0e16aa15984 100644
--- a/source/blender/blenkernel/BKE_library_idmap.h
+++ b/source/blender/blenkernel/BKE_library_idmap.h
@@ -26,8 +26,10 @@ struct IDNameLib_Map;
 struct Main;
 
 struct IDNameLib_Map *BKE_main_idmap_create(
-        struct Main *bmain)
-        ATTR_WARN_UNUSED_RESULT ATTR_NONNULL();
+        struct Main *bmain,
+        const bool create_valid_ids_set,
+        struct Main *old_bmain)
+        ATTR_WARN_UNUSED_RESULT ATTR_NONNULL(1);
 void BKE_main_idmap_destroy(
         struct IDNameLib_Map *id_typemap)
         ATTR_NONNULL();