rtrb 0.4.0

https://crates.io/crates/rtrb/0.4.0

Breaking Changes

• restore synchronization behavior of is_abandoned() (by replacing Arc)
  • dropping a Producer/Consumer on one thread now synchronizes again with calling is_abandoned() on another thread, independent of Rust version

Bug-Fixes

• make ReadChunk::commit()/commit_all() panic-safe (avoid UB caused by double-free)