Function mx_query 

#[unsafe(no_mangle)]
pub unsafe extern "C-unwind" fn mx_query(
    sexp: SEXP,
    tag: mx_tag,
) -> *const c_void

Query an object for an interface vtable by tag.

Returns the vtable pointer, or null if the type does not implement the requested trait.

Registered as "mx_query" via R_RegisterCCallable.

Safety

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