❯ cat manual_test.ml
(* Simple test program for line breakpoints *)

let add x y =           (* Line 3 *)
  x + y                 (* Line 4 *)

let factorial n =       (* Line 6 *)
  let rec loop acc n =  (* Line 7 *)
    if n <= 1 then      (* Line 8 *)
      acc               (* Line 9 *)
    else                (* Line 10 *)
      loop (acc * n) (n - 1)  (* Line 11 *)
  in
  loop 1 n              (* Line 13 *)

let fibonacci n =       (* Line 15 *)
  let rec fib a b n =   (* Line 16 *)
    if n = 0 then a     (* Line 17 *)
    else fib b (a + b) (n - 1)  (* Line 18 *)
  in
  fib 0 1 n             (* Line 20 *)

let () =
  Printf.printf "add 3 5 = %d\n" (add 3 5);
  Printf.printf "factorial 5 = %d\n" (factorial 5);
  Printf.printf "fibonacci 10 = %d\n" (fibonacci 10);
  ()

❯ ./runtime/ocamlrun ./ocamlc -g -I stdlib -use-runtime ./runtime/ocamlrun manual_test.ml -o manual_test
❯ CAML_LD_LIBRARY_PATH=otherlibs/unix:otherlibs/str:otherlibs/systhreads \
  ./runtime/ocamlrun ./debugger/ocamldebug -I stdlib -I otherlibs/unix manual_test
        OCaml Debugger version 5.5.0+dev0-2025-04-28

(ocd) break Manual_test:3
Loading program... done.
Breakpoint 1 at 3:188756: file manual_test.ml, line 4, characters 3-8
(ocd) break Manual_test:6
Breakpoint 2 at 3:188708: file manual_test.ml, line 7, characters 3-209
(ocd) break Manual_test:15
Breakpoint 3 at 3:188592: file manual_test.ml, line 16, characters 3-139
(ocd) info breakpoints
Num    Address  Where
  1 3:    188756  file manual_test.ml, line 4, characters 3-8
  2 3:    188708  file manual_test.ml, line 7, characters 3-209
  3 3:    188592  file manual_test.ml, line 16, characters 3-139
(ocd) run
Time: 18 - pc: 3:188756 - module Manual_test
Breakpoint: 1
4   <|b|>x + y                 (* Line 4 *)