DUK_INTERNAL duk_bool_t duk_js_in(duk_hthread *thr, duk_tval *tv_x, duk_tval *tv_y) {
	duk_context *ctx = (duk_context *) thr;
	duk_bool_t retval;

	/*
	 *  Get the values onto the stack first.  It would be possible to cover
	 *  some normal cases without resorting to the value stack (e.g. if
	 *  lval is already a string).
	 */

	/* XXX: The ES5/5.1/6 specifications require that the key in 'key in obj'
	 * must be string coerced before the internal HasProperty() algorithm is
	 * invoked.  A fast path skipping coercion could be safely implemented for
	 * numbers (as number-to-string coercion has no side effects).  For ES6
	 * proxy behavior, the trap 'key' argument must be in a string coerced
	 * form (which is a shame).
	 */

	/* TypeError if rval is not an object (or lightfunc which should behave
	 * like a Function instance).
	 */
	duk_push_tval(ctx, tv_x);
	duk_push_tval(ctx, tv_y);
	duk_require_type_mask(ctx, -1, DUK_TYPE_MASK_OBJECT | DUK_TYPE_MASK_LIGHTFUNC);
	duk_to_string(ctx, -2);               /* coerce lval with ToString() */

	retval = duk_hobject_hasprop(thr, duk_get_tval(ctx, -1), duk_get_tval(ctx, -2));

	duk_pop_2(ctx);
	return retval;
}

DUK_LOCAL duk_ret_t duk__error_setter_helper(duk_context *ctx, duk_small_uint_t stridx_key) {
	/* Attempt to write 'stack', 'fileName', 'lineNumber' works as if
	 * user code called Object.defineProperty() to create an overriding
	 * own property.  This allows user code to overwrite .fileName etc
	 * intuitively as e.g. "err.fileName = 'dummy'" as one might expect.
	 * See https://github.com/svaarala/duktape/issues/387.
	 */

	DUK_ASSERT_TOP(ctx, 1);  /* fixed arg count: value */

	duk_push_this(ctx);
	duk_push_hstring_stridx(ctx, (duk_small_int_t) stridx_key);
	duk_dup_0(ctx);

	/* [ ... obj key value ] */

	DUK_DD(DUK_DDPRINT("error setter: %!T %!T %!T",
	                   duk_get_tval(ctx, -3), duk_get_tval(ctx, -2), duk_get_tval(ctx, -1)));

	duk_def_prop(ctx, -3, DUK_DEFPROP_HAVE_VALUE |
	                      DUK_DEFPROP_HAVE_WRITABLE | DUK_DEFPROP_WRITABLE |
	                      DUK_DEFPROP_HAVE_ENUMERABLE | /*not enumerable*/
	                      DUK_DEFPROP_HAVE_CONFIGURABLE | DUK_DEFPROP_CONFIGURABLE);
	return 0;
}

DUK_LOCAL void duk__add_compiler_error_line(duk_hthread *thr) {
	duk_context *ctx;

	/* Append a "(line NNN)" to the "message" property of any error
	 * thrown during compilation.  Usually compilation errors are
	 * SyntaxErrors but they can also be out-of-memory errors and
	 * the like.
	 */

	/* [ ... error ] */

	ctx = (duk_context *) thr;
	DUK_ASSERT(duk_is_object(ctx, -1));

	if (!(thr->compile_ctx != NULL && thr->compile_ctx->h_filename != NULL)) {
		return;
	}

	DUK_DDD(DUK_DDDPRINT("compile error, before adding line info: %!T",
	                     (duk_tval *) duk_get_tval(ctx, -1)));

	if (duk_get_prop_stridx(ctx, -1, DUK_STRIDX_MESSAGE)) {
		duk_push_sprintf(ctx, " (line %ld)", (long) thr->compile_ctx->curr_token.start_line);
		duk_concat(ctx, 2);
		duk_put_prop_stridx(ctx, -2, DUK_STRIDX_MESSAGE);
	} else {
		duk_pop(ctx);
	}

	DUK_DDD(DUK_DDDPRINT("compile error, after adding line info: %!T",
	                     (duk_tval *) duk_get_tval(ctx, -1)));
}

DUK_INTERNAL duk_ret_t duk_bi_function_prototype_call(duk_context *ctx) {
	duk_idx_t nargs;

	/* Step 1 is not necessary because duk_call_method() will take
	 * care of it.
	 */

	/* vararg function, thisArg needs special handling */
	nargs = duk_get_top(ctx);  /* = 1 + arg count */
	if (nargs == 0) {
		duk_push_undefined(ctx);
		nargs++;
	}
	DUK_ASSERT(nargs >= 1);

	/* [ thisArg arg1 ... argN ] */

	duk_push_this(ctx);  /* 'func' in the algorithm */
	duk_insert(ctx, 0);

	/* [ func thisArg arg1 ... argN ] */

	DUK_DDD(DUK_DDDPRINT("func=%!iT, thisArg=%!iT, argcount=%ld, top=%ld",
	                     (duk_tval *) duk_get_tval(ctx, 0),
	                     (duk_tval *) duk_get_tval(ctx, 1),
	                     (long) (nargs - 1),
	                     (long) duk_get_top(ctx)));
	duk_call_method(ctx, nargs - 1);
	return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_array_prototype_to_string(duk_context *ctx) {
	(void) duk_push_this_coercible_to_object(ctx);
	duk_get_prop_stridx(ctx, -1, DUK_STRIDX_JOIN);

	/* [ ... this func ] */
	if (!duk_is_callable(ctx, -1)) {
		/* Fall back to the initial (original) Object.toString().  We don't
		 * currently have pointers to the built-in functions, only the top
		 * level global objects (like "Array") so this is now done in a bit
		 * of a hacky manner.  It would be cleaner to push the (original)
		 * function and use duk_call_method().
		 */

		/* XXX: 'this' will be ToObject() coerced twice, which is incorrect
		 * but should have no visible side effects.
		 */
		DUK_DDD(DUK_DDDPRINT("this.join is not callable, fall back to (original) Object.toString"));
		duk_set_top(ctx, 0);
		return duk_bi_object_prototype_to_string(ctx);  /* has access to 'this' binding */
	}

	/* [ ... this func ] */

	duk_insert(ctx, -2);

	/* [ ... func this ] */

	DUK_DDD(DUK_DDDPRINT("calling: func=%!iT, this=%!iT",
	                     (duk_tval *) duk_get_tval(ctx, -2),
	                     (duk_tval *) duk_get_tval(ctx, -1)));
	duk_call_method(ctx, 0);

	return 1;
}

static duk_double_t duk__push_this_number_plain(duk_context *ctx) {
	duk_hobject *h;

	/* Number built-in accepts a plain number or a Number object (whose
	 * internal value is operated on).  Other types cause TypeError.
	 */

	duk_push_this(ctx);
	if (duk_is_number(ctx, -1)) {
		DUK_DDD(DUK_DDDPRINT("plain number value: %!T", (duk_tval *) duk_get_tval(ctx, -1)));
		goto done;
	}
	h = duk_get_hobject(ctx, -1);
	if (!h || 
	    (DUK_HOBJECT_GET_CLASS_NUMBER(h) != DUK_HOBJECT_CLASS_NUMBER)) {
		DUK_DDD(DUK_DDDPRINT("unacceptable this value: %!T", (duk_tval *) duk_get_tval(ctx, -1)));
		DUK_ERROR((duk_hthread *) ctx, DUK_ERR_TYPE_ERROR, "expected a number");
	}
	duk_get_prop_stridx(ctx, -1, DUK_STRIDX_INT_VALUE);
	DUK_ASSERT(duk_is_number(ctx, -1));
	DUK_DDD(DUK_DDDPRINT("number object: %!T, internal value: %!T",
	                     (duk_tval *) duk_get_tval(ctx, -2), (duk_tval *) duk_get_tval(ctx, -1)));
	duk_remove(ctx, -2);

 done:
	return duk_get_number(ctx, -1);
}

DUK_INTERNAL duk_ret_t duk_bi_function_prototype_apply(duk_context *ctx) {
	duk_idx_t len;
	duk_idx_t i;

	DUK_ASSERT_TOP(ctx, 2);  /* not a vararg function */

	duk_push_this(ctx);
	if (!duk_is_callable(ctx, -1)) {
		DUK_DDD(DUK_DDDPRINT("func is not callable"));
		goto type_error;
	}
	duk_insert(ctx, 0);
	DUK_ASSERT_TOP(ctx, 3);

	DUK_DDD(DUK_DDDPRINT("func=%!iT, thisArg=%!iT, argArray=%!iT",
	                     (duk_tval *) duk_get_tval(ctx, 0),
	                     (duk_tval *) duk_get_tval(ctx, 1),
	                     (duk_tval *) duk_get_tval(ctx, 2)));

	/* [ func thisArg argArray ] */

	if (duk_is_null_or_undefined(ctx, 2)) {
		DUK_DDD(DUK_DDDPRINT("argArray is null/undefined, no args"));
		len = 0;
	} else if (!duk_is_object(ctx, 2)) {
		goto type_error;
	} else {
		DUK_DDD(DUK_DDDPRINT("argArray is an object"));

		/* XXX: make this an internal helper */
		duk_get_prop_stridx(ctx, 2, DUK_STRIDX_LENGTH);
		len = (duk_idx_t) duk_to_uint32(ctx, -1);  /* ToUint32() coercion required */
		duk_pop(ctx);

		duk_require_stack(ctx, len);

		DUK_DDD(DUK_DDDPRINT("argArray length is %ld", (long) len));
		for (i = 0; i < len; i++) {
			duk_get_prop_index(ctx, 2, i);
		}
	}
	duk_remove(ctx, 2);
	DUK_ASSERT_TOP(ctx, 2 + len);

	/* [ func thisArg arg1 ... argN ] */

	DUK_DDD(DUK_DDDPRINT("apply, func=%!iT, thisArg=%!iT, len=%ld",
	                     (duk_tval *) duk_get_tval(ctx, 0),
	                     (duk_tval *) duk_get_tval(ctx, 1),
	                     (long) len));
	duk_call_method(ctx, len);
	return 1;

 type_error:
	return DUK_RET_TYPE_ERROR;
}

/* Shared helper to provide toString() and valueOf().  Checks 'this', gets
 * the primitive value to stack top, and optionally coerces with ToString().
 */
duk_ret_t duk_bi_boolean_prototype_tostring_shared(duk_context *ctx) {
	duk_tval *tv;
	duk_hobject *h;
	duk_small_int_t coerce_tostring = duk_get_magic(ctx);

	/* FIXME: there is room to use a shared helper here, many built-ins
	 * check the 'this' type, and if it's an object, check its class,
	 * then get its internal value, etc.
	 */

	duk_push_this(ctx);
	tv = duk_get_tval(ctx, -1);
	DUK_ASSERT(tv != NULL);

	if (DUK_TVAL_IS_BOOLEAN(tv)) {
		goto type_ok;
	} else if (DUK_TVAL_IS_OBJECT(tv)) {
		h = DUK_TVAL_GET_OBJECT(tv);
		DUK_ASSERT(h != NULL);

		if (DUK_HOBJECT_GET_CLASS_NUMBER(h) == DUK_HOBJECT_CLASS_BOOLEAN) {
			duk_get_prop_stridx(ctx, -1, DUK_STRIDX_INT_VALUE);
			DUK_ASSERT(duk_is_boolean(ctx, -1));
			goto type_ok;
		}
	}

	return DUK_RET_TYPE_ERROR;

 type_ok:
	if (coerce_tostring) {
		duk_to_string(ctx, -1);
	}
	return 1;
}

/* Prepare value stack for a method call through an object property.
 * May currently throw an error e.g. when getting the property.
 */
DUK_LOCAL void duk__call_prop_prep_stack(duk_context *ctx, duk_idx_t normalized_obj_idx, duk_idx_t nargs) {
	DUK_ASSERT_CTX_VALID(ctx);

	DUK_DDD(DUK_DDDPRINT("duk__call_prop_prep_stack, normalized_obj_idx=%ld, nargs=%ld, stacktop=%ld",
	                     (long) normalized_obj_idx, (long) nargs, (long) duk_get_top(ctx)));

	/* [... key arg1 ... argN] */

	/* duplicate key */
	duk_dup(ctx, -nargs - 1);  /* Note: -nargs alone would fail for nargs == 0, this is OK */
	duk_get_prop(ctx, normalized_obj_idx);

	DUK_DDD(DUK_DDDPRINT("func: %!T", (duk_tval *) duk_get_tval(ctx, -1)));

	/* [... key arg1 ... argN func] */

	duk_replace(ctx, -nargs - 2);

	/* [... func arg1 ... argN] */

	duk_dup(ctx, normalized_obj_idx);
	duk_insert(ctx, -nargs - 1);

	/* [... func this arg1 ... argN] */
}

DUK_INTERNAL duk_ret_t duk_bi_string_prototype_char_code_at(duk_context *ctx) {
	duk_hthread *thr = (duk_hthread *) ctx;
	duk_int_t pos;
	duk_hstring *h;
	duk_bool_t clamped;

	/* XXX: faster implementation */

	DUK_DDD(DUK_DDDPRINT("arg=%!T", (duk_tval *) duk_get_tval(ctx, 0)));

	h = duk_push_this_coercible_to_string(ctx);
	DUK_ASSERT(h != NULL);

	pos = duk_to_int_clamped_raw(ctx,
	                             0 /*index*/,
	                             0 /*min(incl)*/,
	                             DUK_HSTRING_GET_CHARLEN(h) - 1 /*max(incl)*/,
	                             &clamped /*out_clamped*/);
	if (clamped) {
		duk_push_number(ctx, DUK_DOUBLE_NAN);
		return 1;
	}

	duk_push_u32(ctx, (duk_uint32_t) duk_hstring_char_code_at_raw(thr, h, pos));
	return 1;
}

DUK_EXTERNAL void duk_dump_function(duk_context *ctx) {
	duk_hthread *thr;
	duk_hcompiledfunction *func;
	duk_bufwriter_ctx bw_ctx_alloc;
	duk_bufwriter_ctx *bw_ctx = &bw_ctx_alloc;
	duk_uint8_t *p;

	DUK_ASSERT(ctx != NULL);
	thr = (duk_hthread *) ctx;

	/* Bound functions don't have all properties so we'd either need to
	 * lookup the non-bound target function or reject bound functions.
	 * For now, bound functions are rejected.
	 */
	func = duk_require_hcompiledfunction(ctx, -1);
	DUK_ASSERT(func != NULL);
	DUK_ASSERT(!DUK_HOBJECT_HAS_BOUND(&func->obj));

	/* Estimating the result size beforehand would be costly, so
	 * start with a reasonable size and extend as needed.
	 */
	DUK_BW_INIT_PUSHBUF(thr, bw_ctx, DUK__BYTECODE_INITIAL_ALLOC);
	p = DUK_BW_GET_PTR(thr, bw_ctx);
	*p++ = DUK__SER_MARKER;
	*p++ = DUK__SER_VERSION;
	p = duk__dump_func(ctx, func, bw_ctx, p);
	DUK_BW_SET_PTR(thr, bw_ctx, p);
	DUK_BW_COMPACT(thr, bw_ctx);

	DUK_DD(DUK_DDPRINT("serialized result: %!T", duk_get_tval(ctx, -1)));

	duk_remove(ctx, -2);  /* [ ... func buf ] -> [ ... buf ] */
}

DUK_INTERNAL void duk_hobject_run_finalizer(duk_hthread *thr, duk_hobject *obj) {
	duk_context *ctx = (duk_context *) thr;
	duk_ret_t rc;
#if defined(DUK_USE_ASSERTIONS)
	duk_idx_t entry_top;
#endif

	DUK_DDD(DUK_DDDPRINT("running object finalizer for object: %p", (void *) obj));

	DUK_ASSERT(thr != NULL);
	DUK_ASSERT(ctx != NULL);
	DUK_ASSERT(obj != NULL);
	DUK_ASSERT_VALSTACK_SPACE(thr, 1);

#if defined(DUK_USE_ASSERTIONS)
	entry_top = duk_get_top(ctx);
#endif
	/*
	 *  Get and call the finalizer.  All of this must be wrapped
	 *  in a protected call, because even getting the finalizer
	 *  may trigger an error (getter may throw one, for instance).
	 */

	DUK_ASSERT(!DUK_HEAPHDR_HAS_READONLY((duk_heaphdr *) obj));
	if (DUK_HEAPHDR_HAS_FINALIZED((duk_heaphdr *) obj)) {
		DUK_D(DUK_DPRINT("object already finalized, avoid running finalizer twice: %!O", obj));
		return;
	}
	DUK_HEAPHDR_SET_FINALIZED((duk_heaphdr *) obj);  /* ensure never re-entered until rescue cycle complete */
	if (DUK_HOBJECT_HAS_EXOTIC_PROXYOBJ(obj)) {
		/* This shouldn't happen; call sites should avoid looking up
		 * _Finalizer "through" a Proxy, but ignore if we come here
		 * with a Proxy to avoid finalizer re-entry.
		 */
		DUK_D(DUK_DPRINT("object is a proxy, skip finalizer call"));
		return;
	}

	/* XXX: use a NULL error handler for the finalizer call? */

	DUK_DDD(DUK_DDDPRINT("-> finalizer found, calling wrapped finalize helper"));
	duk_push_hobject(ctx, obj);  /* this also increases refcount by one */
	rc = duk_safe_call(ctx, duk__finalize_helper, NULL /*udata*/, 0 /*nargs*/, 1 /*nrets*/);  /* -> [... obj retval/error] */
	DUK_ASSERT_TOP(ctx, entry_top + 2);  /* duk_safe_call discipline */

	if (rc != DUK_EXEC_SUCCESS) {
		/* Note: we ask for one return value from duk_safe_call to get this
		 * error debugging here.
		 */
		DUK_D(DUK_DPRINT("wrapped finalizer call failed for object %p (ignored); error: %!T",
		                 (void *) obj, (duk_tval *) duk_get_tval(ctx, -1)));
	}
	duk_pop_2(ctx);  /* -> [...] */

	DUK_ASSERT_TOP(ctx, entry_top);
}

DUK_LOCAL duk_ret_t duk__refcount_fake_finalizer(duk_context *ctx) {
	DUK_UNREF(ctx);
	DUK_D(DUK_DPRINT("fake refcount torture finalizer executed"));
#if 0
	DUK_DD(DUK_DDPRINT("fake torture finalizer for: %!T", duk_get_tval(ctx, 0)));
#endif
	/* Require a lot of stack to force a value stack grow/shrink. */
	duk_require_stack(ctx, 100000);

	/* XXX: do something to force a callstack grow/shrink, perhaps
	 * just a manual forced resize?
	 */
	return 0;
}

int duk_builtin_duk_object_addr(duk_context *ctx) {
	duk_tval *tv;
	void *p;

	tv = duk_get_tval(ctx, 0);
	if (!tv || !DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
		return 0;  /* undefined */
	}
	p = (void *) DUK_TVAL_GET_HEAPHDR(tv);

	/* any heap allocated value (string, object, buffer) has a stable pointer */
	duk_push_sprintf(ctx, "%p", p);
	return 1;
}

int duk_builtin_object_constructor_create(duk_context *ctx) {
	duk_hthread *thr = (duk_hthread *) ctx;
	duk_tval *tv;
	duk_hobject *proto = NULL;
	duk_hobject *h;

	DUK_ASSERT_TOP(ctx, 2);

	tv = duk_get_tval(ctx, 0);
	DUK_ASSERT(tv != NULL);
	if (DUK_TVAL_IS_NULL(tv)) {
		;
	} else if (DUK_TVAL_IS_OBJECT(tv)) {
		proto = DUK_TVAL_GET_OBJECT(tv);
		DUK_ASSERT(proto != NULL);
	} else {
		return DUK_RET_TYPE_ERROR;
	}

	/* FIXME: direct helper to create with specific prototype */
	(void) duk_push_object_helper(ctx,
	                              DUK_HOBJECT_FLAG_EXTENSIBLE |
	                              DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_OBJECT),
	                              -1);
	h = duk_get_hobject(ctx, -1);
	DUK_ASSERT(h != NULL);
	DUK_ASSERT(h->prototype == NULL);
	DUK_HOBJECT_SET_PROTOTYPE(thr, h, proto);

	if (!duk_is_undefined(ctx, 1)) {
		/* [ O Properties obj ] */

		/* Use original function.  No need to get it explicitly,
		 * just call the helper.
		 */

		duk_replace(ctx, 0);

		/* [ obj Properties ] */

		return duk_hobject_object_define_properties(ctx);
	}

	/* [ O Properties obj ] */

	return 1;
}

int duk_builtin_duk_object_refc(duk_context *ctx) {
#ifdef DUK_USE_REFERENCE_COUNTING
	duk_tval *tv = duk_get_tval(ctx, 0);
	duk_heaphdr *h;
	if (!tv) {
		return 0;
	}
	if (!DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
		return 0;
	}
	h = DUK_TVAL_GET_HEAPHDR(tv);
	duk_push_int(ctx, DUK_HEAPHDR_GET_REFCOUNT(h));
	return 1;
#else
	return 0;
#endif
}

void duk_hobject_run_finalizer(duk_hthread *thr, duk_hobject *obj) {
	duk_context *ctx = (duk_context *) thr;
	int rc;
#ifdef DUK_USE_ASSERTIONS
	int entry_top;
#endif

	DUK_DDDPRINT("running object finalizer for object: %p", (void *) obj);

	DUK_ASSERT(thr != NULL);
	DUK_ASSERT(ctx != NULL);
	DUK_ASSERT(obj != NULL);

	/* FIXME: assert stack space */

#ifdef DUK_USE_ASSERTIONS
	entry_top = duk_get_top(ctx);
#endif
	/*
	 *  Get and call the finalizer.  All of this must be wrapped
	 *  in a protected call, because even getting the finalizer
	 *  may trigger an error (getter may throw one, for instance).
	 */

	/* FIXME: use a NULL error handler for the finalizer call? */

	DUK_DDDPRINT("-> finalizer found, calling wrapped finalize helper");
	duk_push_hobject(ctx, obj);  /* this also increases refcount by one */
	rc = duk_safe_call(ctx, _finalize_helper, 0 /*nargs*/, 1 /*nrets*/, DUK_INVALID_INDEX);  /* -> [... obj retval/error] */
	DUK_ASSERT_TOP(ctx, entry_top + 2);  /* duk_safe_call discipline */

	if (rc != DUK_ERR_EXEC_SUCCESS) {
		/* Note: we ask for one return value from duk_safe_call to get this
		 * error debugging here.
		 */
		DUK_DPRINT("wrapped finalizer call failed for object %p (ignored); error: %!T",
		           (void *) obj, duk_get_tval(ctx, -1));
	}
	duk_pop_2(ctx);  /* -> [...] */

	DUK_ASSERT_TOP(ctx, entry_top);
}

/* Magic: 0=charCodeAt, 1=codePointAt */
DUK_INTERNAL duk_ret_t duk_bi_string_prototype_char_code_at(duk_context *ctx) {
	duk_hthread *thr = (duk_hthread *) ctx;
	duk_int_t pos;
	duk_hstring *h;
	duk_bool_t clamped;
	duk_uint32_t cp;
	duk_int_t magic;

	/* XXX: faster implementation */

	DUK_DDD(DUK_DDDPRINT("arg=%!T", (duk_tval *) duk_get_tval(ctx, 0)));

	h = duk_push_this_coercible_to_string(ctx);
	DUK_ASSERT(h != NULL);

	pos = duk_to_int_clamped_raw(ctx,
	                             0 /*index*/,
	                             0 /*min(incl)*/,
	                             DUK_HSTRING_GET_CHARLEN(h) - 1 /*max(incl)*/,
	                             &clamped /*out_clamped*/);
#if defined(DUK_USE_ES6)
	magic = duk_get_current_magic(ctx);
#else
	DUK_ASSERT(duk_get_current_magic(ctx) == 0);
	magic = 0;
#endif
	if (clamped) {
		/* For out-of-bounds indices .charCodeAt() returns NaN and
		 * .codePointAt() returns undefined.
		 */
		if (magic != 0) {
			return 0;
		}
		duk_push_nan(ctx);
	} else {
		cp = (duk_uint32_t) duk_hstring_char_code_at_raw(thr, h, pos, (duk_bool_t) magic /*surrogate_aware*/);
		duk_push_u32(ctx, cp);
	}
	return 1;
}

DUK_INTERNAL duk_ret_t duk_bi_object_constructor_create(duk_context *ctx) {
	duk_tval *tv;
	duk_hobject *proto = NULL;

	DUK_ASSERT_TOP(ctx, 2);

	tv = duk_get_tval(ctx, 0);
	DUK_ASSERT(tv != NULL);
	if (DUK_TVAL_IS_NULL(tv)) {
		;
	} else if (DUK_TVAL_IS_OBJECT(tv)) {
		proto = DUK_TVAL_GET_OBJECT(tv);
		DUK_ASSERT(proto != NULL);
	} else {
		return DUK_RET_TYPE_ERROR;
	}

	(void) duk_push_object_helper_proto(ctx,
	                                    DUK_HOBJECT_FLAG_EXTENSIBLE |
	                                    DUK_HOBJECT_CLASS_AS_FLAGS(DUK_HOBJECT_CLASS_OBJECT),
	                                    proto);

	if (!duk_is_undefined(ctx, 1)) {
		/* [ O Properties obj ] */

		/* Use original function.  No need to get it explicitly,
		 * just call the helper.
		 */

		duk_replace(ctx, 0);

		/* [ obj Properties ] */

		return duk_hobject_object_define_properties(ctx);
	}

	/* [ O Properties obj ] */

	return 1;
}

/* Raw helper to extract internal information / statistics about a value.
 * The return values are version specific and must not expose anything
 * that would lead to security issues (e.g. exposing compiled function
 * 'data' buffer might be an issue).  Currently only counts and sizes and
 * such are given so there should not be a security impact.
 */
duk_ret_t duk_bi_duktape_object_info(duk_context *ctx) {
	duk_tval *tv;
	duk_heaphdr *h;
	duk_int_t i, n;

	tv = duk_get_tval(ctx, 0);
	DUK_ASSERT(tv != NULL);  /* because arg count is 1 */

	duk_push_array(ctx);  /* -> [ val arr ] */

	/* type tag (public) */
	duk_push_int(ctx, duk_get_type(ctx, 0));

	/* address */
	if (DUK_TVAL_IS_HEAP_ALLOCATED(tv)) {
		h = DUK_TVAL_GET_HEAPHDR(tv);
		duk_push_pointer(ctx, (void *) h);
	} else {
		goto done;
	}
	DUK_ASSERT(h != NULL);

	/* refcount */
#ifdef DUK_USE_REFERENCE_COUNTING
	duk_push_int(ctx, DUK_HEAPHDR_GET_REFCOUNT(h));
#else
	duk_push_undefined(ctx);
#endif

	/* heaphdr size and additional allocation size, followed by
	 * type specific stuff (with varying value count)
	 */
	switch ((duk_small_int_t) DUK_HEAPHDR_GET_TYPE(h)) {
	case DUK_HTYPE_STRING: {
		duk_hstring *h_str = (duk_hstring *) h;
		duk_push_int(ctx, (int) (sizeof(duk_hstring) + DUK_HSTRING_GET_BYTELEN(h_str) + 1));
		break;
	}
	case DUK_HTYPE_OBJECT: {
		duk_hobject *h_obj = (duk_hobject *) h;
		duk_int_t hdr_size;
		if (DUK_HOBJECT_IS_COMPILEDFUNCTION(h_obj)) {
			hdr_size = (duk_int_t) sizeof(duk_hcompiledfunction);
		} else if (DUK_HOBJECT_IS_NATIVEFUNCTION(h_obj)) {
			hdr_size = (duk_int_t) sizeof(duk_hnativefunction);
		} else if (DUK_HOBJECT_IS_THREAD(h_obj)) {
			hdr_size = (duk_int_t) sizeof(duk_hthread);
		} else {
			hdr_size = (duk_int_t) sizeof(duk_hobject);
		}
		duk_push_int(ctx, (int) hdr_size);
		duk_push_int(ctx, (int) DUK_HOBJECT_E_ALLOC_SIZE(h_obj));
		duk_push_int(ctx, (int) h_obj->e_size);
		duk_push_int(ctx, (int) h_obj->e_used);
		duk_push_int(ctx, (int) h_obj->a_size);
		duk_push_int(ctx, (int) h_obj->h_size);
		if (DUK_HOBJECT_IS_COMPILEDFUNCTION(h_obj)) {
			duk_hbuffer *h_data = ((duk_hcompiledfunction *) h_obj)->data;
			if (h_data) {
				duk_push_int(ctx, DUK_HBUFFER_GET_SIZE(h_data));
			} else {
				duk_push_int(ctx, 0);
			}
		}
		break;
	}
	case DUK_HTYPE_BUFFER: {
		duk_hbuffer *h_buf = (duk_hbuffer *) h;
		if (DUK_HBUFFER_HAS_DYNAMIC(h_buf)) {
			/* XXX: when usable_size == 0, dynamic buf ptr may now be NULL, in which case
			 * the second allocation does not exist.
			 */
			duk_hbuffer_dynamic *h_dyn = (duk_hbuffer_dynamic *) h;
			duk_push_int(ctx, (int) (sizeof(duk_hbuffer_dynamic)));
			duk_push_int(ctx, (int) (DUK_HBUFFER_DYNAMIC_GET_ALLOC_SIZE(h_dyn)));
		} else {
			duk_push_int(ctx, (int) (sizeof(duk_hbuffer_fixed) + DUK_HBUFFER_GET_SIZE(h_buf) + 1));
		}
		break;

	}
	}

 done:
	/* set values into ret array */
	/* FIXME: primitive to make array from valstack slice */
	n = duk_get_top(ctx);
	for (i = 2; i < n; i++) {
		duk_dup(ctx, i);
		duk_put_prop_index(ctx, 1, i - 2);
	}
	duk_dup(ctx, 1);
	return 1;
}