Struct UserdataMarker 

pub struct UserdataMarker<'a> { /* private fields */ }

Public facade over the GC mark accumulator passed to LuaUserdata::trace.

Wraps the crate-internal Marker (private GC primitive in runtime::heap) so embedders never see the gray-stack / weak-table internals. Holds a mutable borrow of the underlying marker for the duration of a single trace call. Constructed only by the collector via the crate-internal __new_internal constructor; embedders cannot synthesize one outside a trace call.

Trace-method contract

Inside LuaUserdata::trace the embedder may only:

• call UserdataMarker::mark / UserdataMarker::mark_value on Gc<...> handles / Values reachable from &self
• read fields of &self

The embedder must not allocate new GC objects, reenter the Vm, take locks, or perform I/O. The trace call runs synchronously inside the collector’s mark phase and must return in bounded wall time.

Implementations

impl<'a> UserdataMarker<'a>

pub fn mark<T>(&mut self, g: Gc<T>) -> bool

Mark a Gc-managed object as reachable. Returns true on the first visit (white → gray transition). Idempotent on later visits within the same cycle.

pub fn mark_value(&mut self, v: Value) -> bool

Convenience: mark every Gc-managed object referenced by a Value. No-op for primitive variants (Int, Float, Bool, Nil, LightUserdata).