Allowed the boot script to check multiple names for the chez executable.

JOLT_TRACE: map tail-frame history to ns/name (file:line)

bin/joltc

@@ -14,7 +14,28 @@
 # JOLT_PWD.
 root="$(CDPATH= cd -- "$(dirname -- "$0")/.." && pwd)"
 export JOLT_PWD="${JOLT_PWD:-$PWD}"
+
+# Identify the Chez Scheme executable
+while read -r CHEZ
+do
+    if [ `which ${CHEZ}` ]
+    then
+	break;
+    fi
+done <<EOF
+chez
+chezscheme
+EOF
+
+# If we failed to find one, whinge and exit.
+if [ ! `which ${CHEZ}` ]
+then
+    echo "No valid Chez Scheme executable found: please install Chez Scheme."
+    exit 1
+fi
+
 # Version for --version / banners: git describe of this checkout, else "dev".
 export JOLT_VERSION="${JOLT_VERSION:-$(git -C "$root" describe --tags --always --dirty 2>/dev/null || echo dev)}"
 cd "$root" || exit 1
-exec chez --script host/chez/cli.ss "$@"
+exec ${CHEZ} --script host/chez/cli.ss "$@"
+

host/chez/build-joltc.ss

@@ -145,11 +145,10 @@
 (scheme-start
   (lambda args
     (set-source-roots! (list \"jolt-core\" \"stdlib\"))
-    (guard (v (#t (jolt-report-throwable v (current-error-port))
+    ;; JOLT_TRACE at RUNTIME (the env is unset at heap-build), before any app ns
-                  (let ((bt (jolt-backtrace-string v)))
+    ;; compiles, so a `-M:run` traces the app's own code.
-                    (when bt (display \"  trace:\\n\" (current-error-port))
+    (jolt-trace-init-from-env!)
-                          (display bt (current-error-port))))
+    (guard (v (#t (jolt-report-throwable v (current-error-port)) (exit 1)))
-                  (exit 1)))
       (cond
         ((and (= (length args) 2) (string=? (car args) \"-e\"))
          (let ((result (jolt-final-str

host/chez/cli.ss

@@ -66,6 +66,9 @@
       (when bt (display "  trace:\n" port) (display bt port)))
     (exit 1)))
 
+;; JOLT_TRACE opt-in, at runtime (before any app ns compiles) so the app is traced.
+(jolt-trace-init-from-env!)
+
 (guard (v (#t (jolt-report-uncaught v)))
   (cond
     ;; -e EXPR — evaluate one expression and print it (blank for nil). Wrapped in

host/chez/compile-eval.ss

@@ -132,11 +132,16 @@
 ;; push is baked in at compile time, only code compiled after this call is traced —
 ;; which is exactly the code you eval / reload in a live session.
 (def-var! "jolt.host" "enable-trace!" jolt-enable-trace!)
-;; Explicit opt-in for a whole run (JOLT_TRACE=1): enable at load, BEFORE any app
+;; Explicit opt-in for a whole run (JOLT_TRACE=1): turn tracing on BEFORE any app
-;; namespace is compiled, so a plain `-M:run` traces the app's own code too. Only an
+;; namespace is compiled, so a plain `-M:run` traces the app's own code too. Called
-;; affirmative value (set, non-empty, not falsey) forces it on here.
+;; from the runtime entrypoints (cli.ss, and the built joltc launcher) — NOT at load
+;; time: a built joltc runs top-level forms at heap-build time, where JOLT_TRACE is
+;; always unset, so a load-time check would never see the user's runtime env. Only an
+;; affirmative value (set, non-empty, not falsey) forces it on.
+(define (jolt-trace-init-from-env!)
   (let ((e (getenv "JOLT_TRACE")))
-  (when (and e (fx>? (string-length e) 0) (not (jolt-trace-env-off? e))) (jolt-enable-trace!)))
+    (when (and e (fx>? (string-length e) 0) (not (jolt-trace-env-off? e)))
+      (jolt-enable-trace!))))
 
 ;; (with-meta sym m) -> sym, else x — an (ns ^:no-doc name …) yields the name with
 ;; reader metadata as a with-meta form; strip it to read the bare ns symbol.

host/chez/joltc-selfbuild-smoke.sh

@@ -42,6 +42,20 @@ if [ "$got_e" != "45" ]; then
   exit 1
 fi
 
+# 2b. JOLT_TRACE must take effect in the BUILT binary. The env check runs at
+# runtime (the launcher), NOT at heap-build where JOLT_TRACE is always unset — so
+# an uncaught error shows a tail-frame trace recovering the TCO-elided chain, and
+# exactly ONE trace block (the launcher must not double-print it).
+got_tr="$(env -i HOME="$HOME" JOLT_TRACE=1 "$joltc" -e '(defn a [x] (+ x 1)) (defn b [x] (a x)) (b :x)' 2>&1)"
+if ! printf '%s' "$got_tr" | grep -q '  trace:' || ! printf '%s' "$got_tr" | grep -q 'b'; then
+  echo "  FAIL: JOLT_TRACE=1 in the built joltc produced no tail-frame trace"
+  echo "--- got ---"; echo "$got_tr"; exit 1
+fi
+if [ "$(printf '%s' "$got_tr" | grep -c '  trace:')" != "1" ]; then
+  echo "  FAIL: built joltc double-printed the trace block"
+  echo "--- got ---"; echo "$got_tr"; exit 1
+fi
+
 # 3. Build an app through the distributed joltc with an EMPTY environment — no
 # PATH at all, so no chez, no cc, no shell tools are reachable. This is the core
 # guarantee: joltc compiles apps entirely on its own.

host/chez/smoke.sh

@@ -124,6 +124,21 @@ if printf '%s' "$err_stale" | grep -q 'h1'; then
 else
   pass=$((pass + 1))
 fi
+# A file-backed project run maps each runtime-compiled frame to ns/name (file:line)
+# — the eval path registers source in trace mode, so the trace isn't bare names.
+tr_proj="$(mktemp -d)"
+mkdir -p "$tr_proj/src/tp"
+printf '{:paths ["src"] :aliases {:run {:main-opts ["-m" "tp.core"]}}}\n' > "$tr_proj/deps.edn"
+printf '(ns tp.core)\n(defn deep [x] (+ x 1))\n(defn mid [x] (inc (deep x)))\n(defn -main [& _] (mid :nan))\n' > "$tr_proj/src/tp/core.clj"
+tr_out="$(JOLT_TRACE=1 JOLT_PWD="$tr_proj" bin/joltc -M:run 2>&1)"
+if printf '%s' "$tr_out" | grep -Eq 'tp\.core/deep \(.*/tp/core\.clj:2\)'; then
+  pass=$((pass + 1))
+else
+  echo "  FAIL: JOLT_TRACE trace should map a frame to ns/name (file:line)"
+  printf '%s\n' "$tr_out" | sed 's/^/    | /'
+  fails=$((fails + 1))
+fi
+rm -rf "$tr_proj"
 
 # --help prints usage, and lists the nREPL server under its real flag name.
 help_out="$(bin/joltc --help 2>/dev/null)"

jolt-core/jolt/backend_scheme.clj

@@ -790,6 +790,21 @@
        (returns-scheme-bool? (:body node) bools'))
      :else false)))
 
+;; In trace mode, a fn def also registers its source so the tail-frame history maps
+;; the recorded frame-name to "ns/name (file:line)" instead of a bare name. Keyed by
+;; the SAME munged name the entry push records (emit-fn's letrec self-binding = the
+;; fn's own name). Returns "" when off / not a positioned fn def, so trace-off output
+;; (seed mint, `jolt build`) is byte-identical. Direct-link builds already register
+;; via emit-def-cached; this covers the open-world eval path.
+(defn- trace-source-reg [node]
+  (let [init (:init node) pos (:pos node)]
+    (if (and @trace-frames? (= :fn (:op init)) (:name init) pos)
+      (str " (jolt-register-source! " (chez-str-lit (munge-name (:name init))) " "
+           (chez-str-lit (:ns node)) " " (chez-str-lit (:name node)) " "
+           (if (:file pos) (chez-str-lit (:file pos)) "jolt-nil") " "
+           (or (:line pos) 0) ")")
+      "")))
+
 (defn emit* [node]
   (case (:op node)
     :const (emit-const (:val node))
@@ -889,7 +904,8 @@
     :fn (emit-fn node)
     ;; (def name) with no init (declare): reserve the cell. A def with non-empty
     ;; reader metadata lowers to def-var-with-meta! (ported in a later increment).
-    :def (cond
+    :def (let [reg (trace-source-reg node)
+               d (cond
                    (:no-init node)
                    (str "(declare-var! " (chez-str-lit (:ns node)) " " (chez-str-lit (:name node)) ")")
                    (jmeta-nonempty? (:meta node))
@@ -897,7 +913,8 @@
                         (emit-with-cells #(emit (:init node))) " " (emit-def-meta node) ")")
                    :else
                    (str "(def-var! " (chez-str-lit (:ns node)) " " (chez-str-lit (:name node)) " "
-                (emit-with-cells #(emit (:init node))) ")"))
+                        (emit-with-cells #(emit (:init node))) ")"))]
+           (if (= reg "") d (str "(begin " d reg ")")))
     (throw (ex-info (str "emit: op not yet ported / unhandled: " (pr-str (:op node))) {}))))
 
 ;; ^:dynamic / ^:redef on a def opts it out of direct-linking: it stays redefinable,