Enum AltrepGuard 

pub enum AltrepGuard {
    Unsafe,
    RustUnwind,
    RUnwind,
}

Controls the panic/error guard used around ALTREP trampoline callbacks.

Each mode trades off safety vs performance:

• Unsafe: No protection. If the callback panics, behavior is undefined (unwinding through C frames). Use only for trivial callbacks that cannot panic.

• RustUnwind: Wraps in catch_unwind, converting Rust panics to R errors. This is the default and safe for all pure-Rust callbacks. Overhead: ~1-2ns per call.

• RUnwind: Wraps in R_UnwindProtect, catching both Rust panics and R longjmp errors. Use when ALTREP callbacks invoke R API functions that might error (e.g., Rf_allocVector, Rf_eval).

The guard is selected via the const GUARD associated constant on the Altrep trait. Since it is a const, the compiler eliminates dead branches at monomorphization time — zero runtime overhead for the chosen mode.

Variants

Unsafe

No protection. Fastest, but if the callback panics, behavior is undefined.

RustUnwind

catch_unwind — catches Rust panics, converts to R errors. Default.

RUnwind

with_r_unwind_protect — catches both Rust panics and R longjmps. Use when ALTREP callbacks invoke R API functions that might error.

Trait Implementations

impl Clone for AltrepGuard

fn clone(&self) -> AltrepGuard

Returns a duplicate of the value.

fn clone_from(&mut self, source: &Self)

Performs copy-assignment from source.

impl Debug for AltrepGuard

fn fmt(&self, f: &mut Formatter<'_>) -> Result

Formats the value using the given formatter.

impl PartialEq for AltrepGuard

fn eq(&self, other: &AltrepGuard) -> bool

Tests for self and other values to be equal, and is used by ==.

fn ne(&self, other: &Rhs) -> bool

Tests for !=. The default implementation is almost always sufficient, and should not be overridden without very good reason.

impl Copy for AltrepGuard

impl Eq for AltrepGuard

impl StructuralPartialEq for AltrepGuard