Empty stack trace for BatString.split depending on I don't know what.

missing_trace.ml

(*
   Both calls to BatString.split and List.assoc below
   raise Not_found. The stack trace shouldn't be empty
   in either case, but it is empty under certain mysterious
   circumstances for BatString.split.
   
   #use "topfind";;
   #require "batteries";;
*)

let debug_this () =
  (* Known to not produce a backtrace sometimes. Trying to find out
     under which conditions *)
  let split_test () =
    try
      ignore (BatString.split "" "x");
      false
    with e ->
      Printexc.get_backtrace () <> ""
  in

  (* Known to produce a backtrace even when BatString.split doesn't *)
  let assoc_test () =
    try
      ignore (List.assoc 0 []);
      false
    with e ->
      Printexc.get_backtrace () <> ""
  in

  Printexc.record_backtrace true;
  assert (assoc_test ());
  Printf.eprintf "***** %s\n%!"
    (if split_test () then "SUCCESS" else "FAILURE")