vm: heap-force builtin-arg wrapper to plug arena-window ref leak

src/eigenscript.c

@@ -625,6 +625,22 @@ Value* make_list(int capacity) {
     return v;
 }
 
+/* Heap-forced list — for VM-internal wrappers that must outlive an arena
+ * window. An arena list freezes val_decref into a no-op, so any heap items
+ * it incref'd via list_append are leaked when the arena is reclaimed.
+ * Used by the builtin-arg packing path: the wrapper holds incref'd args,
+ * and val_decref(arg) must actually walk and release them on return. */
+Value* make_list_heap(int capacity) {
+    Value *v = xcalloc(1, sizeof(Value));
+    v->type = VAL_LIST;
+    v->data.list.capacity = capacity < 8 ? 8 : capacity;
+    v->data.list.items = xcalloc(v->data.list.capacity, sizeof(Value*));
+    v->data.list.count = 0;
+    v->refcount = 1;
+    v->arena = 0;
+    return v;
+}
+
 Value* make_text_builder(void) {
     Value *v = xcalloc(1, sizeof(Value));
     v->type = VAL_TEXT_BUILDER;

src/eigenscript.h

@@ -584,6 +584,7 @@ Value* make_str(const char *s);
 Value* make_str_owned(char *s);
 Value* make_null(void);
 Value* make_list(int capacity);
+Value* make_list_heap(int capacity);
 Value* make_text_builder(void);
 Value* make_fn(const char *name, char **params, int param_count, Env *closure);
 Value* make_builtin(BuiltinFn fn);

src/vm.c

@@ -1525,7 +1525,10 @@ int jit_helper_call(EigsChunk *caller_chunk, int argc, int resume_off) {
         arg = STK_AS_VAL(g_vm.sp - 1);
         val_incref(arg);
     } else {
-        arg = make_list(argc);
+        /* Wrapper must be heap: val_decref(arg) below has to actually
+         * release the list_append increfs on heap items, which an arena
+         * list silently swallows. */
+        arg = make_list_heap(argc);
         for (int i = 0; i < argc; i++) {
             list_append(arg, STK_AS_VAL(g_vm.sp - argc + i));
         }
@@ -2646,7 +2649,8 @@ static Value *vm_run(EigsChunk *chunk, Env *env) {
                 arg = STK_AS_VAL(g_vm.sp - 1);
                 val_incref(arg);
             } else {
-                arg = make_list(argc);
+                /* Heap-forced: see jit_helper_call wrapper rationale. */
+                arg = make_list_heap(argc);
                 for (int i = 0; i < argc; i++) {
                     list_append(arg, STK_AS_VAL(g_vm.sp - argc + i));
                 }