Function jv 

pub unsafe extern "C" fn jv(list1: *mut K, list2: K) -> K

Append a q list object to a q list. Returns a pointer to the (potentially reallocated) K object.

use kdbplus::api::*;
use kdbplus::api::native::*;

#[no_mangle]
pub extern "C" fn concat_list(mut list1: K, list2: K) -> K{
  unsafe{
    jv(&mut list1, list2);
    r1(list1)
  }
}

q)glue: `libc_api_examples 2: (`concat_list; 2);
q)glue[(::; `metals; `fire); ("clay"; 316)]
::
`metals
`fire
"clay"
316
q)glue[1 2 3; 4 5]
1 2 3 4 5
q)glue[`a`b`c; `d`e]
`a`b`c`d`e