Type Alias mx_meth 

pub type mx_meth = unsafe extern "C" fn(data: *mut c_void, argc: i32, argv: *const SEXP) -> SEXP;

Method signature for trait vtable entries.

All trait methods are erased to this uniform signature:

• data: Pointer to the concrete object data
• argc: Number of arguments in argv
• argv: Array of SEXP arguments from R
• Returns: SEXP result to R

Argument Handling

The shim generated by #[miniextendr] on a trait is responsible for:

1. Checking argc matches expected arity
2. Converting each argv[i] via TryFromSexp
3. Calling the actual method
4. Converting the result via IntoR
5. Catching panics and converting to R errors

Safety

This function pointer is unsafe because:

• data must point to valid, properly-aligned data of the expected type
• argv must point to argc valid SEXP values
• Must be called on R’s main thread