Struct RuntimeRoots 

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

Everything the runtime owns that names a GcRef — five arms that keep one alive, and one that only has to keep one valid.

Sealed: the only constructor is RuntimeRoots::from_context, so a collection cannot be run against a hand-picked subset. The six arms are every documented owner of a reference:

arm	strength	owner
shadow	strong	ctx.shadow — the generated shadow stack, scanned [base, top) (ADR-019, ADR-101)
input	strong	ctx.input_source — the read-in buffer
parse_partial	strong	ParseDetail.fail.partial — the best partial parse
snapshot	strong	the runtime-owned CrashSnapshot’s copied locals
native	strong	NativeRootStore — what Rust helpers hold, scanned [0, len) (ADR-114)
debug	weak	ctx.debug_frames + ctx.debug_values — the crash debugger’s live frames and the value slots they name (ADR-104, ADR-106)

abi::maybe_collect builds one of these and passes it whole, so a host-driven allocation and one taken inside the parser interpreter collect against the same arms generated code does.

Why the sixth arm is weak

The debug slots are the over-approximate set: ADR-044 split them from the root set precisely so that making the root set exact would not make the debugger render <uninit> for a local the user can still see in their source. RootSlots::dead nulls a shadow slot at its local’s last use; the debug slot keeps the value, because a value that has been produced stays renderable.

Pushing debug in RootSet::push_roots would undo exactly that split. It is one line, it makes every dead local reachable again, and a_dead_local_stops_being_reachable_from_its_frame is the end-to-end gate that fails when someone writes it — deliberately, and it must keep failing. The arm’s whole content is therefore in WeakSet::clear_reclaimed: the collector decides what dies without consulting the debugger, and then tells the debugger what died.

Implementations

impl<'a> RuntimeRoots<'a>

pub unsafe fn from_context(ctx: *mut RuntimeContext) -> RuntimeRoots<'a>

Read every root arm out of ctx.

Safety

ctx must be null, or point at a live RuntimeContext whose non-null shadow / parse_detail / crash_snapshot / native_roots / debug_frames / debug_values pointers reference live values for 'a. A non-null context’s input_source must be a valid GcRef (RuntimeContext::placeholder documents the same requirement).

Trait Implementations

impl RootSet for RuntimeRoots<'_>

fn push_roots(&self, out: &mut Vec<GcRef>)

Push every root held by this set into out, in any order.

impl WeakSet for RuntimeRoots<'_>

fn clear_reclaimed(&self) -> usize

Null every debug value slot whose object the sweep just reclaimed.

The whole of the weak arm. Called by Heap::collect_inner between the sweep and the return to the allocator — see WeakSet for why nowhere else will do.