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Add WeakRef implementation

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1. Refactor JSObject weak reference list to support different kind of weak reference
2. Support Symbol as WeakMap key
This commit is contained in:
landerlyoung 2024-07-24 18:00:55 +08:00
parent 012451d5f3
commit 2ecaf6cf97
7 changed files with 371 additions and 60 deletions
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4
doc/quickjs.texi
View file

@ -281,9 +281,7 @@ The following features are not supported yet:
@item Tail calls@footnote{We believe the current specification of tails calls is too complicated and presents limited practical interests.}
@item WeakRef and FinalizationRegistry objects
@item Symbols as WeakMap keys
@item FinalizationRegistry objects
@end itemize

1
qjsc.c
View file

@ -77,6 +77,7 @@ static const FeatureEntry feature_list[] = {
#define FE_MODULE_LOADER 9
{ "module-loader", NULL },
{ "bigint", "BigInt" },
{ "weakref", "WeakRef" },
};
void namelist_add(namelist_t *lp, const char *name, const char *short_name,

1
quickjs-atom.h
View file

@ -269,5 +269,6 @@ DEF(Symbol_asyncIterator, "Symbol.asyncIterator")
#ifdef CONFIG_BIGNUM
DEF(Symbol_operatorSet, "Symbol.operatorSet")
#endif
DEF(WeakRef, "WeakRef")
#endif /* DEF */

364
quickjs.c
View file

@ -176,6 +176,7 @@ enum {
JS_CLASS_ASYNC_FROM_SYNC_ITERATOR, /* u.async_from_sync_iterator_data */
JS_CLASS_ASYNC_GENERATOR_FUNCTION, /* u.func */
JS_CLASS_ASYNC_GENERATOR, /* u.async_generator_data */
JS_CLASS_WEAKREF, /* u.weakref */
JS_CLASS_INIT_COUNT, /* last entry for predefined classes */
};
@ -494,6 +495,7 @@ struct JSString {
uint32_t hash : 30;
uint8_t atom_type : 2; /* != 0 if atom, JS_ATOM_TYPE_x */
uint32_t hash_next; /* atom_index for JS_ATOM_TYPE_SYMBOL */
struct list_head *weak_ref_list; /* list of JSWeakRecord */ /* XXX: use a bit and an external hash table? */
#ifdef DUMP_LEAKS
struct list_head link; /* string list */
#endif
@ -883,6 +885,30 @@ struct JSShape {
JSShapeProperty prop[0]; /* prop_size elements */
};
typedef struct JSWeakRecord {
/* operations for given type of weak record, this actually act as a vtable */
const struct JSWeakRecordOperations *operations;
struct list_head list;
} JSWeakRecord;
typedef struct JSWeakRecordOperations {
/* first pass to remove the records from the weak_ref_list
note: implementation CAN NOT touch js context here, eg. new/free js object
*/
void (*reset_weak_ref_first_pass)(JSRuntime *rt, struct JSWeakRecord *wr);
/* second pass to free the values to avoid modifying the weak
reference list while traversing it.
note: implementation is responsible to free node in here. */
void (*reset_weak_ref_second_pass)(JSRuntime *rt, struct JSWeakRecord *wr);
} JSWeakRecordOperations;
typedef struct JSWeakRef {
JSWeakRecord record;
JSObject *this_obj;
JSValueConst target;
} JSWeakRef;
struct JSObject {
union {
JSGCObjectHeader header;
@ -905,7 +931,7 @@ struct JSObject {
JSShape *shape; /* prototype and property names + flag */
JSProperty *prop; /* array of properties */
/* byte offsets: 24/40 */
struct JSMapRecord *first_weak_ref; /* XXX: use a bit and an external hash table? */
struct list_head *weak_ref_list; /* list of JSWeakRecord */ /* XXX: use a bit and an external hash table? */
/* byte offsets: 28/48 */
union {
void *opaque;
@ -929,6 +955,7 @@ struct JSObject {
struct JSAsyncFunctionState *async_function_data; /* JS_CLASS_ASYNC_FUNCTION_RESOLVE, JS_CLASS_ASYNC_FUNCTION_REJECT */
struct JSAsyncFromSyncIteratorData *async_from_sync_iterator_data; /* JS_CLASS_ASYNC_FROM_SYNC_ITERATOR */
struct JSAsyncGeneratorData *async_generator_data; /* JS_CLASS_ASYNC_GENERATOR */
struct JSWeakRef *weakref; /* JS_CLASS_WEAKREF */
struct { /* JS_CLASS_BYTECODE_FUNCTION: 12/24 bytes */
/* also used by JS_CLASS_GENERATOR_FUNCTION, JS_CLASS_ASYNC_FUNCTION and JS_CLASS_ASYNC_GENERATOR_FUNCTION */
struct JSFunctionBytecode *function_bytecode;
@ -1184,7 +1211,6 @@ static int JS_CreateProperty(JSContext *ctx, JSObject *p,
JSValueConst getter, JSValueConst setter,
int flags);
static int js_string_memcmp(const JSString *p1, const JSString *p2, int len);
static void reset_weak_ref(JSRuntime *rt, JSObject *p);
static JSValue js_array_buffer_constructor3(JSContext *ctx,
JSValueConst new_target,
uint64_t len, JSClassID class_id,
@ -1279,6 +1305,21 @@ static JSValue JS_InstantiateFunctionListItem2(JSContext *ctx, JSObject *p,
JSAtom atom, void *opaque);
static JSValue js_object_groupBy(JSContext *ctx, JSValueConst this_val,
int argc, JSValueConst *argv, int is_map);
static void js_init_weak_record(struct JSWeakRecord *wr, const struct JSWeakRecordOperations* operations);
struct list_head **js_get_target_weak_ref_list(JSContext *ctx, JSValueConst target);
static BOOL js_add_weak_ref(JSContext *ctx, struct list_head **weak_ref_list, JSWeakRecord *wr);
static void js_unlink_weak_ref(JSWeakRecord *wr);
static void js_reset_weak_ref(JSRuntime *rt, struct list_head **weak_ref_list);
static inline void js_object_reset_weak_ref(JSRuntime *rt, JSObject *p)
{
assert(p->weak_ref_list);
js_reset_weak_ref(rt, &p->weak_ref_list);
}
static inline void js_atom_reset_weak_ref(JSRuntime *rt, JSAtomStruct *p)
{
assert(p->weak_ref_list);
js_reset_weak_ref(rt, &p->weak_ref_list);
}
static const JSClassExoticMethods js_arguments_exotic_methods;
static const JSClassExoticMethods js_string_exotic_methods;
@ -1901,6 +1942,7 @@ static JSString *js_alloc_string_rt(JSRuntime *rt, int max_len, int is_wide_char
str->atom_type = 0;
str->hash = 0; /* optional but costless */
str->hash_next = 0; /* optional */
str->weak_ref_list = NULL;
#ifdef DUMP_LEAKS
list_add_tail(&str->link, &rt->string_list);
#endif
@ -2070,6 +2112,10 @@ void JS_FreeRuntime(JSRuntime *rt)
for(i = 0; i < rt->atom_size; i++) {
JSAtomStruct *p = rt->atom_array[i];
if (!atom_is_free(p)) {
/* reset weak reference */
if (p->weak_ref_list) {
js_atom_reset_weak_ref(rt, p);
}
#ifdef DUMP_LEAKS
list_del(&p->link);
#endif
@ -2179,6 +2225,7 @@ JSContext *JS_NewContext(JSRuntime *rt)
JS_AddIntrinsicTypedArrays(ctx);
JS_AddIntrinsicPromise(ctx);
JS_AddIntrinsicBigInt(ctx);
JS_AddIntrinsicWeakRef(ctx);
return ctx;
}
@ -2769,6 +2816,7 @@ static JSAtom __JS_NewAtom(JSRuntime *rt, JSString *str, int atom_type)
}
p->header.ref_count = 1; /* not refcounted */
p->atom_type = JS_ATOM_TYPE_SYMBOL;
p->weak_ref_list = NULL;
#ifdef DUMP_LEAKS
list_add_tail(&p->link, &rt->string_list);
#endif
@ -2802,6 +2850,7 @@ static JSAtom __JS_NewAtom(JSRuntime *rt, JSString *str, int atom_type)
p->header.ref_count = 1;
p->is_wide_char = str->is_wide_char;
p->len = str->len;
p->weak_ref_list = NULL;
#ifdef DUMP_LEAKS
list_add_tail(&p->link, &rt->string_list);
#endif
@ -2816,6 +2865,7 @@ static JSAtom __JS_NewAtom(JSRuntime *rt, JSString *str, int atom_type)
p->header.ref_count = 1;
p->is_wide_char = 1; /* Hack to represent NULL as a JSString */
p->len = 0;
p->weak_ref_list = NULL;
#ifdef DUMP_LEAKS
list_add_tail(&p->link, &rt->string_list);
#endif
@ -2924,6 +2974,12 @@ static void JS_FreeAtomStruct(JSRuntime *rt, JSAtomStruct *p)
/* insert in free atom list */
rt->atom_array[i] = atom_set_free(rt->atom_free_index);
rt->atom_free_index = i;
/* release WeakRecord referencing to p */
if (unlikely(p->weak_ref_list)) {
js_atom_reset_weak_ref(rt, p);
}
/* free the string structure */
#ifdef DUMP_LEAKS
list_del(&p->link);
@ -4771,7 +4827,7 @@ static JSValue JS_NewObjectFromShape(JSContext *ctx, JSShape *sh, JSClassID clas
p->is_uncatchable_error = 0;
p->tmp_mark = 0;
p->is_HTMLDDA = 0;
p->first_weak_ref = NULL;
p->weak_ref_list = NULL;
p->u.opaque = NULL;
p->shape = sh;
p->prop = js_malloc(ctx, sizeof(JSProperty) * sh->prop_size);
@ -5459,8 +5515,9 @@ static void free_object(JSRuntime *rt, JSObject *p)
p->shape = NULL;
p->prop = NULL;
if (unlikely(p->first_weak_ref)) {
reset_weak_ref(rt, p);
/* release WeakRecord referencing to p */
if (unlikely(p->weak_ref_list)) {
js_object_reset_weak_ref(rt, p);
}
finalizer = rt->class_array[p->class_id].finalizer;
@ -46971,13 +47028,229 @@ static const JSCFunctionListEntry js_symbol_funcs[] = {
JS_CFUNC_DEF("keyFor", 1, js_symbol_keyFor ),
};
/* JSObject/Atom weak support */
static void js_init_weak_record(struct JSWeakRecord *wr, const struct JSWeakRecordOperations* operations)
{
assert(operations);
init_list_head(&wr->list);
wr->operations = operations;
}
/* find the weak_ref_list of a Object or Symbol/Atom,
on failure: return NULL and throw exception */
struct list_head **js_get_target_weak_ref_list(JSContext *ctx, JSValueConst target)
{
/* the spec says: Thrown if target is not an object or a non-registered symbol. */
if (JS_IsSymbol(target)) {
JSAtomStruct *p = JS_VALUE_GET_PTR(target);
if (p->atom_type == JS_ATOM_TYPE_GLOBAL_SYMBOL) {
JS_ThrowTypeError(ctx, "registered symbol is not allowed");
return NULL;
}
return &p->weak_ref_list;
} else if (JS_IsObject(target)) {
JSObject *p = JS_VALUE_GET_OBJ(target);
return &p->weak_ref_list;
} else {
JS_ThrowTypeError(ctx, "not a valid target");
return NULL;
}
}
/* Add weak record to object's weak reference list, on failure return FALSE and throw exception */
static BOOL js_add_weak_ref(JSContext *ctx, struct list_head **weak_ref_list, JSWeakRecord *wr)
{
if(likely(!*weak_ref_list)) {
struct list_head *list = js_malloc(ctx, sizeof(*list));
if (unlikely(!list)) {
return FALSE;
}
init_list_head(list);
*weak_ref_list = list;
}
list_add(&wr->list, *weak_ref_list);
return TRUE;
}
/* unlink the weak reference from the object weak reference list
eg. JSObject.u.weak_ref_list or JSString.weak_ref_list */
static void js_unlink_weak_ref(JSWeakRecord *wr)
{
list_del(&wr->list);
}
/* reset object weak reference record, and do clean up */
static void js_reset_weak_ref(JSRuntime *rt, struct list_head **weak_ref_list)
{
struct list_head *list = *weak_ref_list;
struct list_head *el, *el1;
/* first pass to remove the records from the Weak... lists */
list_for_each(el, list) {
JSWeakRecord *wr = list_entry(el, JSWeakRecord, list);
assert(wr->operations);
wr->operations->reset_weak_ref_first_pass(rt, wr);
}
/* second pass to free the values to avoid modifying the weak
reference list while traversing it. */
list_for_each_safe(el, el1, list) {
JSWeakRecord *wr = list_entry(el, JSWeakRecord, list);
list_del(el);
assert(wr->operations);
wr->operations->reset_weak_ref_second_pass(rt, wr);
}
js_free_rt(rt, list);
*weak_ref_list = NULL; /* fail safe */
}
/* WeakRef support */
static void js_weakref_reset_weak_ref_first_pass(JSRuntime *rt, JSWeakRecord *wr)
{
JSWeakRef *ref = container_of(wr, JSWeakRef, record);
JSObject *this_obj = ref->this_obj;
assert(this_obj->u.weakref == ref);
assert(!JS_IsUndefined(ref->target));
/* target object deleted, reset weakref */
this_obj->u.weakref = NULL;
}
static void js_weakref_reset_weak_ref_second_pass(JSRuntime *rt, JSWeakRecord *wr)
{
/* delete record */
JSWeakRef *ref = container_of(wr, JSWeakRef, record);
js_free_rt(rt, ref);
}
static const struct JSWeakRecordOperations js_weak_ref_operations = {
js_weakref_reset_weak_ref_first_pass,
js_weakref_reset_weak_ref_second_pass
};
static JSValue js_new_weak_ref_internal(JSContext *ctx, JSValueConst ctor, JSValueConst target)
{
JSValue weak_ref = JS_UNDEFINED;
struct list_head **weak_ref_list = NULL;
weak_ref_list = js_get_target_weak_ref_list(ctx, target);
if (!weak_ref_list) {
goto fail;
}
weak_ref = js_create_from_ctor(ctx, ctor, JS_CLASS_WEAKREF);
if (!JS_IsException(weak_ref)) {
JSObject *obj = JS_VALUE_GET_OBJ(weak_ref);
JSWeakRef *ref = js_malloc(ctx, sizeof(*ref));
if (!ref) {
goto fail;
}
js_init_weak_record(&ref->record, &js_weak_ref_operations);
ref->this_obj = obj;
ref->target = target;
obj->u.weakref = ref;
if (!js_add_weak_ref(ctx, weak_ref_list, &ref->record)) {
goto fail;
}
}
return weak_ref;
fail:
JS_FreeValue(ctx, weak_ref);
return JS_EXCEPTION;
}
JSValue JS_NewWeakRef(JSContext *ctx, JSValueConst target)
{
if (unlikely(!JS_IsRegisteredClass(ctx->rt, JS_CLASS_WEAKREF))) {
return JS_ThrowInternalError(ctx, "WeakRef intrinsic is not added");
}
return js_new_weak_ref_internal(ctx, JS_UNDEFINED, target);
}
JSValue JS_DerefWeakRef(JSContext *ctx, JSValueConst weakref)
{
JSObject *p;
if (!JS_IsObject(weakref)) {
goto fail;
}
p = JS_VALUE_GET_OBJ(weakref);
if (p->class_id != JS_CLASS_WEAKREF) {
goto fail;
}
if (p->u.weakref) {
JSValueConst target = p->u.weakref->target;
return JS_DupValue(ctx, target);
}
return JS_UNDEFINED;
fail:
return JS_ThrowTypeError(ctx, "not a WeakRef");
}
static JSValue js_weakref_constructor(JSContext *ctx, JSValueConst new_target,
int argc, JSValueConst *argv)
{
return js_new_weak_ref_internal(ctx, new_target, argv[0]);
}
static JSValue js_weakref_deref(JSContext *ctx, JSValueConst this_val,
int argc, JSValueConst *argv)
{
return JS_DerefWeakRef(ctx, this_val);
}
static void js_weakref_finalizer(JSRuntime *rt, JSValue val)
{
JSObject *p = JS_VALUE_GET_OBJ(val);
JSWeakRef *ref = p->u.weakref;
if (ref) {
JSWeakRecord *record = &ref->record;
js_unlink_weak_ref(record);
js_free_rt(rt, ref);
}
}
static const JSCFunctionListEntry js_weakref_proto_funcs[] = {
JS_CFUNC_DEF("deref", 0, js_weakref_deref),
JS_PROP_STRING_DEF("[Symbol.toStringTag]", "WeakRef", JS_PROP_CONFIGURABLE ),
};
static const JSClassShortDef js_weak_class_def[] = {
{ JS_ATOM_WeakRef, js_weakref_finalizer, NULL },
};
void JS_AddIntrinsicWeakRef(JSContext *ctx)
{
JSValue proto;
if (!JS_IsRegisteredClass(ctx->rt, JS_CLASS_WEAKREF)) {
init_class_range(ctx->rt, js_weak_class_def, JS_CLASS_WEAKREF,
countof(js_weak_class_def));
}
proto = JS_NewObject(ctx);
ctx->class_proto[JS_CLASS_WEAKREF] = proto;
JS_SetPropertyFunctionList(ctx, proto,
js_weakref_proto_funcs,
countof(js_weakref_proto_funcs));
JS_NewGlobalCConstructorOnly(ctx, "WeakRef",
js_weakref_constructor, 1,
proto);
}
/* Set/Map/WeakSet/WeakMap */
typedef struct JSMapRecord {
int ref_count; /* used during enumeration to avoid freeing the record */
BOOL empty; /* TRUE if the record is deleted */
struct JSMapState *map;
struct JSMapRecord *next_weak_ref;
JSWeakRecord weak_record; /* managed by JSObject.weak_ref_list */
struct list_head link;
struct list_head hash_link;
JSValue key;
@ -47205,6 +47478,14 @@ static void map_hash_resize(JSContext *ctx, JSMapState *s)
s->record_count_threshold = new_hash_size * 2;
}
static void js_map_reset_weak_ref_first_pass(JSRuntime *rt, JSWeakRecord *wr);
static void js_map_reset_weak_ref_second_pass(JSRuntime *rt, JSWeakRecord *wr);
static const JSWeakRecordOperations js_map_weak_operations = {
js_map_reset_weak_ref_first_pass,
js_map_reset_weak_ref_second_pass,
};
static JSMapRecord *map_add_record(JSContext *ctx, JSMapState *s,
JSValueConst key)
{
@ -47218,10 +47499,13 @@ static JSMapRecord *map_add_record(JSContext *ctx, JSMapState *s,
mr->map = s;
mr->empty = FALSE;
if (s->is_weak) {
JSObject *p = JS_VALUE_GET_OBJ(key);
struct list_head **weak_ref_list = js_get_target_weak_ref_list(ctx, key);
js_init_weak_record(&mr->weak_record, &js_map_weak_operations);
/* Add the weak reference */
mr->next_weak_ref = p->first_weak_ref;
p->first_weak_ref = mr;
if (!weak_ref_list || !js_add_weak_ref(ctx, weak_ref_list, &mr->weak_record)) {
js_free(ctx, mr);
return NULL;
}
} else {
JS_DupValue(ctx, key);
}
@ -47236,34 +47520,13 @@ static JSMapRecord *map_add_record(JSContext *ctx, JSMapState *s,
return mr;
}
/* Remove the weak reference from the object weak
reference list. we don't use a doubly linked list to
save space, assuming a given object has few weak
references to it */
static void delete_weak_ref(JSRuntime *rt, JSMapRecord *mr)
{
JSMapRecord **pmr, *mr1;
JSObject *p;
p = JS_VALUE_GET_OBJ(mr->key);
pmr = &p->first_weak_ref;
for(;;) {
mr1 = *pmr;
assert(mr1 != NULL);
if (mr1 == mr)
break;
pmr = &mr1->next_weak_ref;
}
*pmr = mr1->next_weak_ref;
}
static void map_delete_record(JSRuntime *rt, JSMapState *s, JSMapRecord *mr)
{
if (mr->empty)
return;
list_del(&mr->hash_link);
if (s->is_weak) {
delete_weak_ref(rt, mr);
js_unlink_weak_ref(&mr->weak_record);
} else {
JS_FreeValueRT(rt, mr->key);
}
@ -47290,30 +47553,21 @@ static void map_decref_record(JSRuntime *rt, JSMapRecord *mr)
}
}
static void reset_weak_ref(JSRuntime *rt, JSObject *p)
static void js_map_reset_weak_ref_first_pass(JSRuntime *rt, JSWeakRecord *wr)
{
JSMapRecord *mr, *mr_next;
JSMapState *s;
JSMapRecord *mr = container_of(wr, JSMapRecord, weak_record);
JSMapState *s = mr->map;
assert(s->is_weak);
assert(!mr->empty); /* no iterator on WeakMap/WeakSet */
list_del(&mr->hash_link);
list_del(&mr->link);
}
/* first pass to remove the records from the WeakMap/WeakSet
lists */
for(mr = p->first_weak_ref; mr != NULL; mr = mr->next_weak_ref) {
s = mr->map;
assert(s->is_weak);
assert(!mr->empty); /* no iterator on WeakMap/WeakSet */
list_del(&mr->hash_link);
list_del(&mr->link);
}
/* second pass to free the values to avoid modifying the weak
reference list while traversing it. */
for(mr = p->first_weak_ref; mr != NULL; mr = mr_next) {
mr_next = mr->next_weak_ref;
JS_FreeValueRT(rt, mr->value);
js_free_rt(rt, mr);
}
p->first_weak_ref = NULL; /* fail safe */
static void js_map_reset_weak_ref_second_pass(JSRuntime *rt, JSWeakRecord *wr)
{
JSMapRecord *mr = container_of(wr, JSMapRecord, weak_record);
JS_FreeValueRT(rt, mr->value);
js_free_rt(rt, mr);
}
static JSValue js_map_set(JSContext *ctx, JSValueConst this_val,
@ -47326,8 +47580,6 @@ static JSValue js_map_set(JSContext *ctx, JSValueConst this_val,
if (!s)
return JS_EXCEPTION;
key = map_normalize_key(ctx, argv[0]);
if (s->is_weak && !JS_IsObject(key))
return JS_ThrowTypeErrorNotAnObject(ctx);
if (magic & MAGIC_SET)
value = JS_UNDEFINED;
else
@ -47597,7 +47849,7 @@ static void js_map_finalizer(JSRuntime *rt, JSValue val)
mr = list_entry(el, JSMapRecord, link);
if (!mr->empty) {
if (s->is_weak)
delete_weak_ref(rt, mr);
js_unlink_weak_ref(&mr->weak_record);
else
JS_FreeValueRT(rt, mr->key);
JS_FreeValueRT(rt, mr->value);

5
quickjs.h
View file

@ -376,6 +376,7 @@ void JS_AddIntrinsicPromise(JSContext *ctx);
void JS_AddIntrinsicBigInt(JSContext *ctx);
void JS_AddIntrinsicBigFloat(JSContext *ctx);
void JS_AddIntrinsicBigDecimal(JSContext *ctx);
void JS_AddIntrinsicWeakRef(JSContext *ctx);
/* enable operator overloading */
void JS_AddIntrinsicOperators(JSContext *ctx);
/* enable "use math" */
@ -1077,6 +1078,10 @@ int JS_SetModuleExport(JSContext *ctx, JSModuleDef *m, const char *export_name,
int JS_SetModuleExportList(JSContext *ctx, JSModuleDef *m,
const JSCFunctionListEntry *tab, int len);
/* WeakRef support */
JSValue JS_NewWeakRef(JSContext *ctx, JSValueConst target);
JSValue JS_DerefWeakRef(JSContext *ctx, JSValueConst weakref);
#undef js_unlikely
#undef js_force_inline

2
test262.conf
View file

@ -204,7 +204,7 @@ Uint32Array
Uint8Array
Uint8ClampedArray
WeakMap
WeakRef=skip
WeakRef
WeakSet
well-formed-json-stringify

54
tests/test_builtin.js
View file

@ -779,6 +779,59 @@ function test_weak_map()
tab[i][0] = null; /* should remove the object from the WeakMap too */
}
/* the WeakMap should be empty here */
// test symbol as key
var symbol_key = Symbol("key");
a = new WeakMap();
a.set(symbol_key, "hello");
assert(a.has(symbol_key), true);
assert(a.get(symbol_key), "hello");
symbol_key = undefined;
assert(a.has(symbol_key), false);
assert(a.get(symbol_key), undefined);
}
function test_weak_ref()
{
var obj = {};
var ref = new WeakRef(obj);
var ref2 = new WeakRef(obj);
assert(ref.deref(), obj);
assert(ref2.deref(), obj);
obj = undefined;
/* weak ref should be released */
assert(ref.deref(), undefined);
assert(ref2.deref(), undefined);
// symbol
var sym = Symbol("sym")
var ref3 = new WeakRef(sym);
assert(ref3.deref(), sym);
new WeakRef(Symbol.hasInstance);
sym = undefined;
assert(ref3.deref(), undefined);
function should_fail(block) {
try {
block()
} catch (e) {
return
}
throw_error("weak ref should throw exception, but it not");
}
should_fail(() => new WeakRef("string"));
should_fail(() => new WeakRef(/* number */0));
should_fail(() => new WeakRef(/* registered symbol */ Symbol.for("test")));
/* cyclic ref */
obj = {};
ref = new WeakRef(obj);
obj["x"] = ref;
}
function test_generator()
@ -855,4 +908,5 @@ test_regexp();
test_symbol();
test_map();
test_weak_map();
test_weak_ref();
test_generator();