tcc_callback: Register an R function as a callback

In Rtinycc: Builds the 'TinyCC' Command-Line Interface and Library for 'C' Scripting in 'R'

Register an R function as a callback

Description

Wraps an R function so it can be passed as a C function pointer to compiled code. The callback will be invoked via a trampoline that marshals arguments between C and R.

Usage

tcc_callback(fun, signature, threadsafe = FALSE)

Arguments

fun	An R function to be called from C
signature	C function signature string (e.g., "double (*)(int, double)")
threadsafe	Whether to enable thread-safe invocation (experimental)

Details

Thread safety: callbacks are executed on the R main thread only. Invoking a callback from a worker thread is unsupported and may crash R. The threadsafe flag is currently informational only.

If a callback raises an error, a warning is emitted and a type-appropriate default value is returned.

When binding callbacks with tcc_bind(), use a ⁠callback:<signature>⁠ argument type so a synchronous trampoline is generated. The trampoline expects a ⁠void*⁠ user-data pointer as its first argument; pass tcc_callback_ptr(cb) as the user-data argument to the C API. For thread-safe usage from worker threads, use ⁠callback_async:<signature>⁠ which schedules the call on the main thread and returns a default value.

Pointer arguments (e.g., double*, int*) are passed as external pointers. Lengths must be supplied separately if needed.

The return type may be any scalar type supported by the FFI mappings (e.g., i32, f64, bool, cstring), or SEXP to return an R object directly.

Callback lifetime: callbacks are eventually released by finalizers and package unload. Call tcc_callback_close() when you want deterministic invalidation and earlier release of the preserved R function.

Value

A tcc_callback object (externalptr wrapper)

Rtinycc documentation built on April 28, 2026, 1:07 a.m.