ocaml: wire dynamic-wind through CEK — WindFrame + winders stack

- sx_types.ml: CallccContinuation gains winders depth int field
- sx_runtime.ml: make_callcc_continuation(captured, winders_len),
  callcc_continuation_winders_len accessor; get_val maps after-thunk,
  winders-len, body-result to cf_f/cf_extra/cf_name
- sx_ref.ml: step_limit/step_count restored; make_wind_after_frame and
  make_wind_return_frame now store their args in the CekFrame fields
- transpiler.sx: after-thunk→cf_f, winders-len→cf_extra,
  body-result→cf_name for future bootstrap runs
- 8 new dynamic-wind tests pass (OCaml), 235/235 no regressions

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hosts/ocaml/lib/sx_runtime.ml

@@ -46,7 +46,7 @@ let sx_call f args =
     !Sx_types._cek_eval_lambda_ref f args
   | Continuation (k, _) ->
     k (match args with x :: _ -> x | [] -> Nil)
-  | CallccContinuation _ ->
+  | CallccContinuation (_, _) ->
     raise (Eval_error "callcc continuations must be invoked through the CEK machine")
   | _ ->
     let nargs = List.length args in
@@ -156,6 +156,9 @@ let get_val container key =
      | "extra" -> f.cf_extra | "extra2" -> f.cf_extra2
      | "subscribers" -> f.cf_results
      | "prev-tracking" -> f.cf_extra
+     | "after-thunk" -> f.cf_f        (* wind-after frame *)
+     | "winders-len" -> f.cf_extra    (* wind-after frame *)
+     | "body-result" -> f.cf_name     (* wind-return frame *)
      | _ -> Nil)
   | VmFrame f, String k ->
     (match k with
@@ -381,15 +384,20 @@ let continuation_data v = match v with
   | _ -> raise (Eval_error "not a continuation")
 
 (* Callcc (undelimited) continuation support *)
-let callcc_continuation_p v = match v with CallccContinuation _ -> Bool true | _ -> Bool false
+let callcc_continuation_p v = match v with CallccContinuation (_, _) -> Bool true | _ -> Bool false
 
-let make_callcc_continuation captured =
+let make_callcc_continuation captured winders_len =
-  CallccContinuation (sx_to_list captured)
+  let n = match winders_len with Number f -> int_of_float f | Integer n -> n | _ -> 0 in
+  CallccContinuation (sx_to_list captured, n)
 
 let callcc_continuation_data v = match v with
-  | CallccContinuation frames -> List frames
+  | CallccContinuation (frames, _) -> List frames
   | _ -> raise (Eval_error "not a callcc continuation")
 
+let callcc_continuation_winders_len v = match v with
+  | CallccContinuation (_, n) -> Number (float_of_int n)
+  | _ -> Number 0.0
+
 (* Dynamic wind — simplified for OCaml (no async) *)
 let host_error msg =
   raise (Eval_error (value_to_str msg))

hosts/ocaml/lib/sx_types.ml

@@ -57,7 +57,7 @@ and value =
   | Macro  of macro
   | Thunk  of value * env
   | Continuation of (value -> value) * dict option
-  | CallccContinuation of value list  (** Undelimited continuation — captured kont frames *)
+  | CallccContinuation of value list * int  (** Undelimited continuation — captured kont frames + winders depth at capture *)
   | NativeFn of string * (value list -> value)
   | Signal of signal
   | RawHTML of string
@@ -476,7 +476,7 @@ let type_of = function
   | Macro _        -> "macro"
   | Thunk _        -> "thunk"
   | Continuation (_, _) -> "continuation"
-  | CallccContinuation _ -> "continuation"
+  | CallccContinuation (_, _) -> "continuation"
   | NativeFn _     -> "function"
   | Signal _       -> "signal"
   | RawHTML _      -> "raw-html"
@@ -506,7 +506,7 @@ let is_signal = function
 let is_record = function Record _ -> true | _ -> false
 
 let is_callable = function
-  | Lambda _ | NativeFn _ | Continuation (_, _) | CallccContinuation _ | VmClosure _ -> true
+  | Lambda _ | NativeFn _ | Continuation (_, _) | CallccContinuation (_, _) | VmClosure _ -> true
   | _ -> false
 
 
@@ -815,7 +815,7 @@ let rec inspect = function
     Printf.sprintf "<%s(%s)>" tag (String.concat ", " m.m_params)
   | Thunk _ -> "<thunk>"
   | Continuation (_, _) -> "<continuation>"
-  | CallccContinuation _ -> "<callcc-continuation>"
+  | CallccContinuation (_, _) -> "<callcc-continuation>"
   | NativeFn (name, _) -> Printf.sprintf "<native:%s>" name
   | Signal _ -> "<signal>"
   | RawHTML s -> Printf.sprintf "\"<raw-html:%d>\"" (String.length s)

hosts/ocaml/transpiler.sx

@@ -256,6 +256,7 @@
     "callcc-continuation?"
     "callcc-continuation-data"
     "make-callcc-continuation"
+    "callcc-continuation-winders-len"
     "dynamic-wind-call"
     "strip-prefix"
     "component-set-param-types!"
@@ -295,7 +296,8 @@
     "*bind-tracking*"
     "*provide-batch-depth*"
     "*provide-batch-queue*"
-    "*provide-subscribers*"))
+    "*provide-subscribers*"
+    "*winders*"))
 
 (define
   ml-is-mutable-global?
@@ -533,13 +535,13 @@
               "; cf_env = "
               (ef "env")
               "; cf_name = "
-              (if (= frame-type "if") (ef "else") (ef "name"))
+              (if (= frame-type "if") (ef "else") (cond (some (fn (k) (= k "body-result")) items) (ef "body-result") :else (ef "name")))
               "; cf_body = "
               (if (= frame-type "if") (ef "then") (ef "body"))
               "; cf_remaining = "
               (ef "remaining")
               "; cf_f = "
-              (ef "f")
+              (cond (some (fn (k) (= k "after-thunk")) items) (ef "after-thunk") (some (fn (k) (= k "f")) items) (ef "f") :else "Nil")
               "; cf_args = "
               (cond
                 (some (fn (k) (= k "evaled")) items)
@@ -582,6 +584,8 @@
                 (ef "prev-tracking")
                 (some (fn (k) (= k "extra")) items)
                 (ef "extra")
+                (some (fn (k) (= k "winders-len")) items)
+                (ef "winders-len")
                 :else "Nil")
               "; cf_extra2 = "
               (cond