Struct Marker 

pub struct Marker { /* private fields */ }

Holds the gray queue during a mark phase. Passed to Trace::trace.

Implementations

impl Marker

pub fn mark<T: Trace + 'static>(&mut self, gc: Gc<T>)

Mark a Gc<T> as gray (reachable, but its outgoing edges not yet traced). Called by Trace::trace implementations.

Per-cycle dedup uses visited (a HashSet of box identities) rather than the color flag. Color-based dedup would silently skip new_uncollected boxes left Black by the previous cycle — those allocations are NOT on the heap’s allgc chain, so the start-of-mark “reset all allgc to White” loop does not reach them, and a Black uncollected box would be skipped without re-tracing its children (causing reachable allgc descendants to be swept). The visited set is rebuilt every full_collect (Marker::new), so this dedup is always per-cycle.

pub fn try_visit(&mut self, addr: usize) -> bool

Record that an Rc-backed object (GcRef<T> in Phase A-D-0) has been visited and return whether this is the first visit. Used by recursive Trace impls to break cycles while the real Gc<T> gray-queue path is not yet wired (e.g. _G._G == _G would otherwise infinitely recurse).

pub fn is_visited(&self, id: usize) -> bool

True iff id was reached during the mark phase. Used by the post-mark hook (Heap::full_collect_with_post_mark) to decide whether a weak-table entry’s target is still strongly reachable. Read-only — callers cannot add entries.

pub fn visited_count(&self) -> usize

Number of objects marked so far. Used by the post-mark hook’s ephemeron-convergence fixed-point loop to detect when an iteration added no new reachable objects and the loop can terminate.

pub fn drain_gray_queue(&mut self)

Drain the gray queue, transitively marking children. Each gray box becomes black; its Trace::trace is called so the children it points at get pushed onto the queue. Repeats until the queue is empty.

Exposed for the post-mark hook so it can run ephemeron convergence: after marking new values via Marker::mark (or value.trace(self)), the hook calls drain_gray_queue to propagate the new reachability, then re-checks for fixed-point.