Struct SlotStackHeader 

pub struct SlotStackHeader<T: Copy> { /* private fields */ }

The three-word header generated code bump-allocates against.

#[repr(C)] and pointer-shaped rather than index-shaped: the prologue’s whole job is top → zero → top + n*8, and holding raw addresses makes that three instructions with no base-plus-scaled-index arithmetic.

The fields stay private and the backend reaches top through Self::TOP_OFFSET. That is strictly better than making the field pub so the backend can offset_of! it: the displacement is still derived from the #[repr(C)] layout at compile time, but no other crate can write the field.

Generic in the slot type because the mechanism is not specific to GC roots; see SlotStack.

Implementations

impl<T: Copy> SlotStackHeader<T>

pub const TOP_OFFSET: i32

The byte offset of top within the header, for the backend to emit as a load/store displacement. Computed from the #[repr(C)] layout so it stays correct if the struct evolves.

pub fn claimed(&self) -> &[T]

Every frame currently on the stack, concatenated — the collector’s door for the shadow instantiation, and the crash snapshot’s for the debug ones.

pub fn len(&self) -> usize

How many slots are currently claimed. Zero between runs, if every prologue was balanced by an epilogue.

pub fn is_empty(&self) -> bool

True iff no frame is on the stack.