Function fz_pool_array_append 

pub unsafe extern "C" fn fz_pool_array_append(
    ctx: *mut fz_context,
    arr: *mut fz_pool_array,
    idx: *mut usize,
) -> *mut c_void

Append an element to the end of the array.

Returns a pointer to the new element (initially all 0’s), and
(optionally) the index of that element.