Function XLENGTH 

unsafe fn XLENGTH(x: SEXP) -> R_xlen_t

Get the length of a SEXP as R_xlen_t (supports long vectors).

ALTREP-aware: will call ALTREP Length method if needed. Checked wrapper for XLENGTH. Calls XLENGTH_unchecked and routes through with_r_thread. Generated from source location line 2265, column 8. Generated from source file miniextendr-api/src/ffi.rs.