This looks like a optimizer bug where it makes wrong assumptions. The code inside lib_id_delete:264 on rBafd13710b897cc1c11b `for (id = last_remapped_id->next; id; id = id->next) {..}` is not executed in release/relwithdebinfo builds. This can be "fixed" by several ways: - Adding a line that prints the `last_remapped_id->name` right before the said for-loop starts. - Turning off optimization for the whole function `id_delete`: `#pragma clang optimize off/on` Ray Molenkamp - Marking `last_remapped_id` volatile. Julian Eisel - Marking `tagged_deleted_ids` volatile. But it adds a warning when calling `BLI_addtail`: discards volatile qualifier. Discovered by accident. Fix T81077 Reviewed By: mont29 Maniphest Tasks: T81077 Differential Revision: https://developer.blender.org/D9315