Module allocator 

R-backed global allocator for Rust.

Allocations are backed by R RAWSXP objects and protected from GC via R_PreserveObject/R_ReleaseObject (R’s precious list).

Protection Strategy

This allocator uses R_PreserveObject directly because:

• Allocations may need to survive across multiple .Call invocations
• The SEXP (RAWSXP) is its own handle — zero Rust-side bookkeeping
• LIFO release pattern (recently allocated = first freed) means O(1) release in practice (R’s precious list scans from head)

See the crate-level documentation for an overview of miniextendr’s protection mechanisms.

Layout

Layout inside the RAWSXP (bytes): [optional leading pad][Header][user bytes…]

We always return a pointer aligned to at least: max(requested_align, align_of::<Header>()) so the Header placed immediately before the user pointer is always aligned.

⚠️ Warning: longjmp Risk

R’s Rf_allocVector can longjmp on allocation failure instead of returning NULL. If this happens, Rust destructors will NOT run, potentially causing:

• Resource leaks (files, locks, etc.)
• Corrupted state if allocation happens mid-operation

This allocator is best suited for:

• Short-lived operations within a single R API call
• Contexts where R_UnwindProtect is active (e.g., inside run_on_worker)

For long-lived allocations or critical cleanup requirements, consider using Rust’s standard allocator instead.

Structs

Header 🔒

Metadata stored immediately before the returned user pointer.

RAllocator

R-backed global allocator.

Constants

HEADER_ALIGN 🔒

HEADER_SIZE 🔒

Functions

alloc_main_thread 🔒 ^⚠

Allocate memory on the R main thread.

dealloc_main_thread 🔒 ^⚠

Deallocate memory on the R main thread.

realloc_main_thread 🔒 ^⚠

Reallocate memory on the R main thread.

sendable_data_ptr_get 🔒

sendable_data_ptr_is_null 🔒

sendable_data_ptr_new 🔒

sendable_data_ptr_null 🔒

with_r_thread_or_inline 🔒

Routes a closure to the R main thread if not already there.

Type Aliases

SendableDataPtr 🔒

Wrapper to make *mut u8 pointers Send for cross-thread routing.