Struct OwnedProtect 

pub struct OwnedProtect {
    sexp: SEXP,
    armed: bool,
    _nosend: PhantomData<Rc<()>>,
}

A single-object RAII guard: PROTECT on create, UNPROTECT(1) on drop.

Use this for simple cases where you’re protecting a single value and don’t need the batching benefits of ProtectScope.

Example

unsafe fn allocate_and_fill() -> SEXP {
    let guard = OwnedProtect::new(Rf_allocVector(REALSXP, 10));
    fill_vector(guard.get());
    // Return the SEXP - guard drops and unprotects on this line.
    // This is safe because no GC can occur between unprotect and return.
    guard.get()
}

Warning: Stack Ordering

OwnedProtect uses UNPROTECT(1), which removes the top of the protection stack. If you have nested protections from other sources, the drop order matters!

For complex scenarios, prefer ProtectScope which unprotects all its values at once when dropped.

Fields

sexp: SEXP

armed: bool

_nosend: PhantomData<Rc<()>>

Implementations

impl OwnedProtect

pub unsafe fn new(x: SEXP) -> Self

Create a new protection guard for x.

Calls Rf_protect(x) immediately.

Safety

• Must be called from the R main thread
• x must be a valid SEXP

pub fn get(&self) -> SEXP

Get the protected SEXP.

pub unsafe fn forget(self)

Escape hatch: do not UNPROTECT(1) on drop.

Safety

Leaks one protection entry unless unprotected elsewhere.

Methods from Deref<Target = SEXP>

pub fn is_null_ptr(self) -> bool

Is this SEXP a C null pointer (address 0x0)?

This answers a pointer question, not an R question. An SEXP that R hands you (a .Call() argument, a list element, an attribute) is never a C null pointer: R’s NULL is the R_NilValue singleton, a real object at a non-zero address. A C null pointer only shows up where C code uses address zero for “nothing here”: an uninitialised static or field (SEXP::null()), an ALTREP data1/data2 slot that was never set, or an FFI function that returns NULL on failure.

To ask “is this R’s NULL?”, use SEXP::is_nil().

use miniextendr_api::SEXP;

let unset = SEXP::null();
assert!(unset.is_null_ptr());

There is no SEXP::is_null(): the name read like a test for R’s NULL, so it is gone on purpose.

use miniextendr_api::SEXP;

let unset = SEXP::null();
assert!(unset.is_null());

See also: SEXP::is_nil(), SEXP::is_null_or_nil(), SEXP::null()

pub fn is_nil(self) -> bool

Is this SEXP R’s NULL (R_NilValue)?

This is the check for an R value: an optional argument that defaults to NULL, an absent attribute, an empty list slot. It compares the address against the R_NilValue singleton and never dereferences self, so it is safe on a stale SEXP. A C null pointer is not R’s NULL; for that, use SEXP::is_null_ptr().

use miniextendr_api::SEXP;

// `x` is an argument whose R default is `NULL`: `f()` and `f(NULL)`
// both arrive as `R_NilValue`.
fn given(x: SEXP) -> bool {
    !x.is_nil()
}

See also: SEXP::nil(), SEXP::is_null_ptr(), SEXP::is_null_or_nil()

pub fn is_null_or_nil(self) -> bool

Is this SEXP either a C null pointer or R’s NULL?

For a slot that can hold either kind of “nothing”: unset (address zero) or set to R_NilValue, such as an external pointer’s protected value. For an R value alone, SEXP::is_nil() is the right check.

use miniextendr_api::SEXP;

// A slot that was never set counts as empty.
assert!(SEXP::null().is_null_or_nil());

See also: SEXP::is_nil(), SEXP::is_null_ptr()

pub fn as_ptr(self) -> *mut SEXPREC

Get the raw pointer.

pub unsafe fn altrep_data1_raw(self) -> SEXP

Get the raw SEXP in the ALTREP data1 slot.

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

pub unsafe fn altrep_data1_raw_unchecked(self) -> SEXP

Get the raw SEXP in the ALTREP data1 slot (unchecked — no thread routing).

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

pub unsafe fn set_altrep_data1(self, v: SEXP)

Set the ALTREP data1 slot.

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

pub unsafe fn altrep_data2_raw(self) -> SEXP

Get the raw SEXP in the ALTREP data2 slot.

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

pub unsafe fn altrep_data2_raw_unchecked(self) -> SEXP

Get the raw SEXP in the ALTREP data2 slot (unchecked — no thread routing).

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

pub unsafe fn set_altrep_data2(self, v: SEXP)

Set the ALTREP data2 slot.

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

pub unsafe fn set_altrep_data2_unchecked(self, v: SEXP)

Set the ALTREP data2 slot (unchecked — no thread routing).

Safety

• self must be a valid ALTREP SEXP
• Must be called from the R main thread

Trait Implementations

impl Deref for OwnedProtect

type Target = SEXP

The resulting type after dereferencing.

fn deref(&self) -> &Self::Target

Dereferences the value.

impl Drop for OwnedProtect

fn drop(&mut self)

Executes the destructor for this type.

fn pin_drop(self: Pin<&mut Self>)

🔬This is a nightly-only experimental API. (pin_ergonomics)

Execute the destructor for this type, but different to Drop::drop, it requires self to be pinned.

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference's “Type Layout” chapter for details on type layout guarantees.

Size: 16 bytes