Function begin

codegraph-kernel/src/stack.rs:126–142

Arm the guard for one extraction on the calling thread: clear the latch and (re)compute the threshold. OS bounds are computed once per thread; the fallback budget is re-anchored at every call's entry stack pointer.

()

/// and (re)compute the threshold. OS bounds are computed once per thread;
/// the fallback budget is re-anchored at every call's entry stack pointer.
pub fn begin() {
    OVERFLOWED.with(|o| o.set(false));
    let cached = THRESHOLD.with(|t| t.get());
    if cached != 0 && THRESHOLD_IS_OS.with(|f| f.get()) {
        return;
    }
    match os_stack_low() {
        Some(low) => {
            THRESHOLD.with(|t| t.set(low.saturating_add(RED_ZONE)));
            THRESHOLD_IS_OS.with(|f| f.set(true));
        }
        None => {
            THRESHOLD.with(|t| t.set(current_sp().saturating_sub(FALLBACK_BUDGET).max(1)));
            THRESHOLD_IS_OS.with(|f| f.set(false));
        }
    }
}

/// `true` once the walker has descended to within `RED_ZONE` of the stack
/// limit. Latches `OVERFLOWED` so `run_guarded` can discard the result. A