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erlang: Phase 10b slice — real OP_BIF_LENGTH handler, end-to-end VM proof

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giles
2026-05-15 08:43:45 +00:00
parent 33725de03b
commit 5c7ad01bd1
2 changed files with 78 additions and 6 deletions
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37
hosts/ocaml/lib/extensions/erlang_ext.ml
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@@ -64,6 +64,41 @@ module M : Sx_vm_extension.EXTENSION = struct
(id, nm, (fun (_vm : Sx_vm.vm) (_frame : Sx_vm.frame) ->
bump (); not_wired nm))
in
(* Phase 10b vertical slice: one REAL register-machine handler.
erlang.OP_BIF_LENGTH (230) — pops an Erlang list off the VM
stack and pushes its length. Proves the full path works:
extension-opcode-id -> bytecode -> Sx_vm dispatch fallthrough
-> this handler -> correct stack result. The remaining 17
opcodes still raise not_wired until their handlers + compiler
emission land. Erlang lists are tagged dicts:
nil = {"tag" -> String "nil"}
cons = {"tag" -> String "cons"; "head" -> v; "tail" -> v} *)
let er_tag d =
match Hashtbl.find_opt d "tag" with
| Some (String s) -> s | _ -> ""
in
let op_bif_length =
(230, "erlang.OP_BIF_LENGTH",
(fun (vm : Sx_vm.vm) (_frame : Sx_vm.frame) ->
bump ();
let v = Sx_vm.pop vm in
let rec walk acc node =
match node with
| Dict d ->
(match er_tag d with
| "nil" -> acc
| "cons" ->
(match Hashtbl.find_opt d "tail" with
| Some t -> walk (acc + 1) t
| None -> raise (Eval_error
"erlang.OP_BIF_LENGTH: cons cell without :tail"))
| _ -> raise (Eval_error
"erlang.OP_BIF_LENGTH: not a proper list"))
| _ -> raise (Eval_error
"erlang.OP_BIF_LENGTH: not a proper list")
in
Sx_vm.push vm (Integer (walk 0 v))))
in
[
op 222 "erlang.OP_PATTERN_TUPLE";
op 223 "erlang.OP_PATTERN_LIST";
@@ -73,7 +108,7 @@ module M : Sx_vm_extension.EXTENSION = struct
op 227 "erlang.OP_RECEIVE_SCAN";
op 228 "erlang.OP_SPAWN";
op 229 "erlang.OP_SEND";
op 230 "erlang.OP_BIF_LENGTH";
op_bif_length;
op 231 "erlang.OP_BIF_HD";
op 232 "erlang.OP_BIF_TL";
op 233 "erlang.OP_BIF_ELEMENT";