Struct SaveSnapshot 

pub struct SaveSnapshot {
    pub d_stack_depth: usize,
    pub packing_mode: bool,
    pub vm_alloc_mode: bool,
    pub object_format: i32,
    pub gstate: GraphicsState,
    pub gstate_stack: Vec<GstateEntry>,
    pub gstate_store_len: usize,
    pub marks: VmMarks,
}

Interpreter state captured by save and reinstated by restore.

Grouped into a struct rather than passed positionally: every field is state the interpreter has to rewind, and the set grows as more of the interpreter learns to participate in save/restore.

Fields

d_stack_depth: usize

d_stack length at save time (for restore validation).

packing_mode: bool

Packing mode (setpacking/currentpacking).

vm_alloc_mode: bool

VM allocation mode (setglobal/currentglobal).

object_format: i32

Binary object format (setobjectformat/currentobjectformat).

gstate: GraphicsState

Graphics state and graphics state stack.

gstate_stack: Vec<GstateEntry>

gstate_store_len: usize

Context::gstate_store length at save time.

gstate_store backs PsValue::Gstate, and a gstate object is a composite in local VM, so restore has to reclaim the ones created after the save. Without this the store would grow monotonically and each stale slot would keep naming entities the restore released.

marks: VmMarks

Local-VM high-water marks, for reclamation on restore.