CHANGELOG.md

[0.5.3]

• Adds a Collect impl for hashbrown::HashTable.

[0.5.2]

• Add the ability to transition from a fully marked arena immediately into CollectionPhase::Collecting.

[0.5.1]

• Correct the behavior of Arena::mark_debt and Arena::mark_all to do what their documentation suggest and do nothing during CollectionPhase::Collecting
• Implement Collect for std::collections::LinkedList
• Make StaticCollect<T> #[repr(transparent)], to support sound casting from Gc<StaticCollect<T>> to Gc<T>.

[0.5.0]

This release adds the concept of "finalization" to arenas. At the end of the "mark" phase, at the moment that an arena is considered "fully marked" and is ready to transition to the "sweep" phase, the "fully marked" arena can be examined with some special powers...

MarkedArena::finalize can be called to check which pointers are considered "dead" for this collection cycle. A "dead" pointer is one that is destined (without further changes) to be freed during the next "sweep" phase. You can "resurrect" these pointers either through normal root mutation before entering the "sweep" phase, or more simply by calling explicit resurrect methods on those pointers. Any resurrection, whether through mutation or resurrect methods, immediately makes the arena no longer fully marked, but the arena can then be re-marked and re-examined.

This simple, safe API (examining a "fully marked" arena for potentially dead pointers, performing mutation, then potentially re-marking and re-examining) is enough to implement quite complex garbage collector behavior. It can be used to implement "finalizer" methods on objects, "ephemeron tables", Java-style "reference queues" and more.

Release Highlights

• New Finalization API.
• New API to query the current phase of the collector.
• Fixup the pacing algorithm for correctness and simplicity. Makes Pacing::with_timing_factor(0.0) actually work correctly for stop-the-world collection.
• GcWeak::is_dropped now works only during collection, not mutation.
• Add more trait impls to StaticCollect.
• Gc::ptr_eq and GcWeak::ptr_eq now ignore metadata of dyn pointers, matching the behavior of Rc::ptr_eq and Arc::ptr_eq.

[0.4.0]

This release adds the ability to track external allocations (allocations which are not stored in a Gc<T>) which also participate in pacing the garbage collector. There is now a new (feature-gated) type allocator_api::MetricsAlloc which implements the allocator-api2::Allocator trait which can be used to automatically track the external allocation of collection types.

This release also adds (feature-gated) tracing support, which emits a span per GC phase (propagate, sweep, drop), and events when collection resumes and yields.

Release Highlights

• Tracked external allocations API which participates in GC pacing.
• Feature-gated support for a allocator_api2::Allocator implementation that automatically tracks allocation.
• Feature-gated support for hashbrown types, to automatically implement Collect on them.
• Feature-gated tracing support.
• Implement Collect for Box<T: ?Sized>.
• Add methods to project Write<Option<T>> and Write<Result<T, E>>.
• Don't fail to build by trying to implement Collect on Arc<T> for platforms without Arc.

[0.3.3]

• Actually pause for the configured amount of time in the gc, rather than the minimum.

[0.3.2]

• Implement Eq, PartialEq, Ord, PartialOrd, and Hash traits on Gc<T> similar to the traits on std smart pointers like Rc<T>.
• Relax unnecessary bounds on Collect impls of std collections.
• Make Arena::remembered_size() return reasonable values.

[0.3.1]

• Fallible DynamicRootSet API.

[0.3.0]

An enormous number of breaking API changes, too many to list, almost the entire API has been rethought.

The credit goes mostly to others for the release, @Bale001, @Aaron1011, @dragazo, and especially @moulins.

Release Highlights

• New Arena API that does not require macros and instead uses a Rootable trait and HRTBs for lifetime projection.
• Methods on Arena to directly mutate the root type and map the root from one type to another.
• A new API for 'static roots that are held in smart pointers (DynamicRootSet).
• Gc pointers can now point to DSTs, and there is an unsize! macro for unsizing coercions to replace the unstable Unsize trait.
• Weak pointers!
• GcCell has been replaced by explicit public lock types held within Gc pointers with safe ways of mutating them.
• Field projection on held lock types to allow for separate locks held within a single Gc pointer to be safely mutated.
• Unsafe Gc pointer coercions to compatible pointee types.
• Soundly get references to Gc types with &'gc lifetime.
• More ergonomic Mutation and Collection context types.
• Tons of correctness and soundness fixes.

This release also completely drops the gc-sequence combinator crate. Because of other API changes, anything you could do with gc-sequence before can almost certainly be expressed better either using the new 'static root API or with the new map API. See this comment for a bit more info.

[0.2.2]

• No changes, fixing a release snafu with cargo-release

[0.2.1]

• Allow using #[collect(require_static)] on fields
• Add no_std compatibility for gc-arena and gc-sequence
• Add Collect impl for VecDeque, PhantomData`.
• Add #[track_caller] for better panic error messages
• Improve error messages for proc-macro derived Collect implementations substantially.
• Improve generated code for Context::allocate in release builds.

[0.2]

• API incompatible change: depend on proc-macro2, quote, and syn 1.0
• API incompatible change: update synstructure to 0.12
• API incompatible change: use the trick from the pin-project crate to prevent types from implementing Drop by making it cause a conflicting impl of a MustNotImplDrop trait.
• API incompatible change: Add #[collect(no_drop)] and remove the empty_drop and require_copy versions since they are now less useful than no_drop.