Function mx_get 

#[unsafe(no_mangle)]
pub unsafe extern "C-unwind" fn mx_get(sexp: SEXP) -> *mut mx_erased

Extract an erased object pointer from an R external pointer.

Returns null if the SEXP is not an external pointer or doesn’t carry the miniextendr tag.

Registered as "mx_get" via R_RegisterCCallable.

Safety

sexp must be a valid SEXP. Must be called on R’s main thread.