summaryrefslogtreecommitdiffstats
path: root/js/src/vm/Realm.cpp
blob: 4e3eba5677f4c3825c684245cb50c4fcf2f2dbe0 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*-
 * vim: set ts=8 sts=2 et sw=2 tw=80:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "js/shadow/Realm.h"  // JS::shadow::Realm
#include "vm/Realm-inl.h"

#include "mozilla/MemoryReporting.h"

#include <stddef.h>

#include "jsfriendapi.h"

#include "builtin/WrappedFunctionObject.h"
#include "debugger/DebugAPI.h"
#include "debugger/Debugger.h"
#include "gc/GC.h"
#include "jit/JitRuntime.h"
#include "js/CallAndConstruct.h"      // JS::IsCallable
#include "js/friend/ErrorMessages.h"  // js::GetErrorMessage, JSMSG_*
#include "js/GCVariant.h"
#include "js/Proxy.h"
#include "js/RootingAPI.h"
#include "js/Wrapper.h"
#include "vm/Compartment.h"
#include "vm/DateTime.h"
#include "vm/Iteration.h"
#include "vm/JSContext.h"
#include "vm/PIC.h"

#include "gc/Marking-inl.h"
#include "vm/JSObject-inl.h"

using namespace js;

Realm::DebuggerVectorEntry::DebuggerVectorEntry(js::Debugger* dbg_,
                                                JSObject* link)
    : dbg(dbg_), debuggerLink(link) {}

ObjectRealm::ObjectRealm(JS::Zone* zone)
    : innerViews(zone, zone), iteratorCache(zone) {}

Realm::Realm(Compartment* comp, const JS::RealmOptions& options)
    : JS::shadow::Realm(comp),
      zone_(comp->zone()),
      runtime_(comp->runtimeFromMainThread()),
      creationOptions_(options.creationOptions()),
      behaviors_(options.behaviors()),
      objects_(zone_),
      randomKeyGenerator_(runtime_->forkRandomKeyGenerator()),
      debuggers_(zone_),
      allocatedDuringIncrementalGC_(zone_->isGCMarkingOrSweeping() ||
                                    zone_->isGCFinished()),
      wasm(runtime_) {
  runtime_->numRealms++;
}

Realm::~Realm() {
  MOZ_ASSERT(!hasBeenEnteredIgnoringJit());
  MOZ_ASSERT(!isDebuggee());

  // Write the code coverage information in a file.
  if (lcovRealm_) {
    runtime_->lcovOutput().writeLCovResult(*lcovRealm_);
  }

  if (allocationMetadataBuilder_) {
    forgetAllocationMetadataBuilder();
  }

  MOZ_ASSERT(runtime_->numRealms > 0);
  runtime_->numRealms--;
}

void Realm::init(JSContext* cx, JSPrincipals* principals) {
  /*
   * As a hack, we clear our timezone cache every time we create a new realm.
   * This ensures that the cache is always relatively fresh, but shouldn't
   * interfere with benchmarks that create tons of date objects (unless they
   * also create tons of iframes, which seems unlikely).
   */
  js::ResetTimeZoneInternal(ResetTimeZoneMode::DontResetIfOffsetUnchanged);

  if (principals) {
    // Any realm with the trusted principals -- and there can be
    // multiple -- is a system realm.
    isSystem_ = (principals == cx->runtime()->trustedPrincipals());
    JS_HoldPrincipals(principals);
    principals_ = principals;
  }
}

bool JSRuntime::createJitRuntime(JSContext* cx) {
  using namespace js::jit;

  MOZ_ASSERT(!jitRuntime_);

  if (!CanLikelyAllocateMoreExecutableMemory()) {
    // Try to release memory first instead of potentially reporting OOM below.
    if (OnLargeAllocationFailure) {
      OnLargeAllocationFailure();
    }
  }

  jit::JitRuntime* jrt = cx->new_<jit::JitRuntime>();
  if (!jrt) {
    return false;
  }

  // Unfortunately, initialization depends on jitRuntime_ being non-null, so
  // we can't just wait to assign jitRuntime_.
  jitRuntime_ = jrt;

  if (!jitRuntime_->initialize(cx)) {
    js_delete(jitRuntime_.ref());
    jitRuntime_ = nullptr;
    return false;
  }

  return true;
}

#ifdef JSGC_HASH_TABLE_CHECKS

void js::DtoaCache::checkCacheAfterMovingGC() {
  MOZ_ASSERT(!str || !IsForwarded(str));
}

#endif  // JSGC_HASH_TABLE_CHECKS

NonSyntacticLexicalEnvironmentObject*
ObjectRealm::getOrCreateNonSyntacticLexicalEnvironment(JSContext* cx,
                                                       HandleObject enclosing,
                                                       HandleObject key,
                                                       HandleObject thisv) {
  MOZ_ASSERT(&ObjectRealm::get(enclosing) == this);

  if (!nonSyntacticLexicalEnvironments_) {
    auto map = cx->make_unique<ObjectWeakMap>(cx);
    if (!map) {
      return nullptr;
    }

    nonSyntacticLexicalEnvironments_ = std::move(map);
  }

  RootedObject lexicalEnv(cx, nonSyntacticLexicalEnvironments_->lookup(key));

  if (!lexicalEnv) {
    MOZ_ASSERT(key->is<NonSyntacticVariablesObject>() ||
               !key->is<EnvironmentObject>());
    lexicalEnv =
        NonSyntacticLexicalEnvironmentObject::create(cx, enclosing, thisv);
    if (!lexicalEnv) {
      return nullptr;
    }
    if (!nonSyntacticLexicalEnvironments_->add(cx, key, lexicalEnv)) {
      return nullptr;
    }
  }

  return &lexicalEnv->as<NonSyntacticLexicalEnvironmentObject>();
}

NonSyntacticLexicalEnvironmentObject*
ObjectRealm::getOrCreateNonSyntacticLexicalEnvironment(JSContext* cx,
                                                       HandleObject enclosing) {
  // If a wrapped WithEnvironmentObject was passed in, unwrap it, as we may
  // be creating different WithEnvironmentObject wrappers each time.
  RootedObject key(cx, enclosing);
  if (enclosing->is<WithEnvironmentObject>()) {
    MOZ_ASSERT(!enclosing->as<WithEnvironmentObject>().isSyntactic());
    key = &enclosing->as<WithEnvironmentObject>().object();
  }

  // NOTE: The default global |this| value is set to key for compatibility
  // with existing users of the lexical environment cache.
  //  - When used by shared-global JSM loader, |this| must be the
  //    NonSyntacticVariablesObject passed as enclosing.
  //  - When used by SubscriptLoader, |this| must be the target object of
  //    the WithEnvironmentObject wrapper.
  //  - When used by XBL/DOM Events, we execute directly as a function and
  //    do not access the |this| value.
  // See js::GetFunctionThis / js::GetNonSyntacticGlobalThis
  return getOrCreateNonSyntacticLexicalEnvironment(cx, enclosing, key,
                                                   /*thisv = */ key);
}

NonSyntacticLexicalEnvironmentObject*
ObjectRealm::getNonSyntacticLexicalEnvironment(JSObject* key) const {
  MOZ_ASSERT(&ObjectRealm::get(key) == this);

  if (!nonSyntacticLexicalEnvironments_) {
    return nullptr;
  }
  // If a wrapped WithEnvironmentObject was passed in, unwrap it as in
  // getOrCreateNonSyntacticLexicalEnvironment.
  if (key->is<WithEnvironmentObject>()) {
    MOZ_ASSERT(!key->as<WithEnvironmentObject>().isSyntactic());
    key = &key->as<WithEnvironmentObject>().object();
  }
  JSObject* lexicalEnv = nonSyntacticLexicalEnvironments_->lookup(key);
  if (!lexicalEnv) {
    return nullptr;
  }
  return &lexicalEnv->as<NonSyntacticLexicalEnvironmentObject>();
}

void Realm::traceGlobalData(JSTracer* trc) {
  // Trace things reachable from the realm's global. Note that these edges
  // must be swept too in case the realm is live but the global is not.

  savedStacks_.trace(trc);

  DebugAPI::traceFromRealm(trc, this);
}

void ObjectRealm::trace(JSTracer* trc) {
  if (objectMetadataTable) {
    objectMetadataTable->trace(trc);
  }

  if (nonSyntacticLexicalEnvironments_) {
    nonSyntacticLexicalEnvironments_->trace(trc);
  }
}

void Realm::traceRoots(JSTracer* trc,
                       js::gc::GCRuntime::TraceOrMarkRuntime traceOrMark) {
  // It's not possible to trigger a GC between allocating the pending object and
  // setting its meta data in ~AutoSetNewObjectMetadata.
  MOZ_RELEASE_ASSERT(!objectPendingMetadata_);

  if (!JS::RuntimeHeapIsMinorCollecting()) {
    // The global is never nursery allocated, so we don't need to
    // trace it when doing a minor collection.
    //
    // If a realm is on-stack, we mark its global so that JSContext::global()
    // remains valid.
    if (shouldTraceGlobal() && global_) {
      TraceRoot(trc, global_.unbarrieredAddress(), "on-stack realm global");
    }

    // If the realm is still being initialized we set a flag so that it doesn't
    // get deleted, since there may be GC things that contain pointers to it.
    if (shouldTraceGlobal() && initializingGlobal_) {
      allocatedDuringIncrementalGC_ = true;
    }
  }

  // Nothing below here needs to be treated as a root if we aren't marking
  // this zone for a collection.
  if (traceOrMark == js::gc::GCRuntime::MarkRuntime &&
      !zone()->isCollectingFromAnyThread()) {
    return;
  }

  /* Mark debug scopes, if present */
  if (debugEnvs_) {
    debugEnvs_->trace(trc);
  }

  objects_.trace(trc);
}

void ObjectRealm::finishRoots() {
  if (objectMetadataTable) {
    objectMetadataTable->clear();
  }

  if (nonSyntacticLexicalEnvironments_) {
    nonSyntacticLexicalEnvironments_->clear();
  }
}

void Realm::finishRoots() {
  if (debugEnvs_) {
    debugEnvs_->finish();
  }

  objects_.finishRoots();
}

void ObjectRealm::sweepAfterMinorGC(JSTracer* trc) {
  InnerViewTable& table = innerViews.get();
  if (table.needsSweepAfterMinorGC()) {
    table.sweepAfterMinorGC(trc);
  }
}

void Realm::sweepAfterMinorGC(JSTracer* trc) {
  globalWriteBarriered = 0;
  dtoaCache.purge();
  objects_.sweepAfterMinorGC(trc);
}

void Realm::traceWeakSavedStacks(JSTracer* trc) { savedStacks_.traceWeak(trc); }

void Realm::traceWeakGlobalEdge(JSTracer* trc) {
  // If the global is dead, free its GlobalObjectData.
  auto result = TraceWeakEdge(trc, &global_, "Realm::global_");
  if (result.isDead()) {
    result.initialTarget()->releaseData(runtime_->gcContext());
  }
}

void Realm::traceWeakDebugEnvironmentEdges(JSTracer* trc) {
  if (debugEnvs_) {
    debugEnvs_->traceWeak(trc);
  }
}

void Realm::fixupAfterMovingGC(JSTracer* trc) {
  purge();
  traceWeakGlobalEdge(trc);
}

void Realm::purge() {
  dtoaCache.purge();
  newProxyCache.purge();
  newPlainObjectWithPropsCache.purge();
  plainObjectAssignCache.purge();
  objects_.iteratorCache.clearAndCompact();
  arraySpeciesLookup.purge();
  promiseLookup.purge();

  if (zone()->isGCPreparing()) {
    purgeForOfPicChain();
  }
}

void Realm::purgeForOfPicChain() {
  if (GlobalObject* global = global_.unbarrieredGet()) {
    if (NativeObject* object = global->getForOfPICObject()) {
      ForOfPIC::Chain* chain = ForOfPIC::fromJSObject(object);
      chain->freeAllStubs(runtime_->gcContext());
    }
  }
}

// Check to see if this individual realm is recording allocations. Debuggers or
// runtimes can try and record allocations, so this method can check to see if
// any initialization is needed.
bool Realm::isRecordingAllocations() { return !!allocationMetadataBuilder_; }

void Realm::setAllocationMetadataBuilder(
    const js::AllocationMetadataBuilder* builder) {
  // Clear any jitcode in the runtime, which behaves differently depending on
  // whether there is a creation callback.
  if (bool(allocationMetadataBuilder_) != bool(builder)) {
    ReleaseAllJITCode(runtime_->gcContext());
    if (builder) {
      zone()->incNumRealmsWithAllocMetadataBuilder();
    } else {
      zone()->decNumRealmsWithAllocMetadataBuilder();
    }
  }

  allocationMetadataBuilder_ = builder;
}

void Realm::forgetAllocationMetadataBuilder() {
  if (!allocationMetadataBuilder_) {
    return;
  }

  // Unlike setAllocationMetadataBuilder, we don't have to discard all JIT
  // code here (code is still valid, just a bit slower because it doesn't do
  // inline GC allocations when a metadata builder is present), but we do want
  // to cancel off-thread Ion compilations to avoid races when Ion accesses
  // numRealmsWithAllocMetadataBuilder_ off-thread.
  CancelOffThreadIonCompile(zone());

  zone()->decNumRealmsWithAllocMetadataBuilder();

  allocationMetadataBuilder_ = nullptr;
}

void Realm::setNewObjectMetadata(JSContext* cx, HandleObject obj) {
  MOZ_ASSERT(obj->maybeCCWRealm() == this);
  cx->check(compartment(), obj);

  AutoEnterOOMUnsafeRegion oomUnsafe;
  if (JSObject* metadata =
          allocationMetadataBuilder_->build(cx, obj, oomUnsafe)) {
    MOZ_ASSERT(metadata->maybeCCWRealm() == obj->maybeCCWRealm());
    cx->check(metadata);

    if (!objects_.objectMetadataTable) {
      auto table = cx->make_unique<ObjectWeakMap>(cx);
      if (!table) {
        oomUnsafe.crash("setNewObjectMetadata");
      }

      objects_.objectMetadataTable = std::move(table);
    }

    if (!objects_.objectMetadataTable->add(cx, obj, metadata)) {
      oomUnsafe.crash("setNewObjectMetadata");
    }
  }
}

void Realm::updateDebuggerObservesFlag(unsigned flag) {
  MOZ_ASSERT(isDebuggee());
  MOZ_ASSERT(flag == DebuggerObservesAllExecution ||
             flag == DebuggerObservesCoverage ||
             flag == DebuggerObservesAsmJS || flag == DebuggerObservesWasm ||
             flag == DebuggerObservesNativeCall);

  GlobalObject* global =
      zone()->runtimeFromMainThread()->gc.isForegroundSweeping()
          ? unsafeUnbarrieredMaybeGlobal()
          : maybeGlobal();
  bool observes = false;
  if (flag == DebuggerObservesAllExecution) {
    observes = DebugAPI::debuggerObservesAllExecution(global);
  } else if (flag == DebuggerObservesCoverage) {
    observes = DebugAPI::debuggerObservesCoverage(global);
  } else if (flag == DebuggerObservesAsmJS) {
    observes = DebugAPI::debuggerObservesAsmJS(global);
  } else if (flag == DebuggerObservesWasm) {
    observes = DebugAPI::debuggerObservesWasm(global);
  } else if (flag == DebuggerObservesNativeCall) {
    observes = DebugAPI::debuggerObservesNativeCall(global);
  }

  if (observes) {
    debugModeBits_ |= flag;
  } else {
    debugModeBits_ &= ~flag;
  }
}

void Realm::setIsDebuggee() {
  if (!isDebuggee()) {
    debugModeBits_ |= IsDebuggee;
    runtimeFromMainThread()->incrementNumDebuggeeRealms();
  }
}

void Realm::unsetIsDebuggee() {
  if (isDebuggee()) {
    if (debuggerObservesCoverage()) {
      runtime_->decrementNumDebuggeeRealmsObservingCoverage();
    }
    debugModeBits_ = 0;
    DebugEnvironments::onRealmUnsetIsDebuggee(this);
    runtimeFromMainThread()->decrementNumDebuggeeRealms();
  }
}

void Realm::updateDebuggerObservesCoverage() {
  bool previousState = debuggerObservesCoverage();
  updateDebuggerObservesFlag(DebuggerObservesCoverage);
  if (previousState == debuggerObservesCoverage()) {
    return;
  }

  if (debuggerObservesCoverage()) {
    // Interrupt any running interpreter frame. The scriptCounts are
    // allocated on demand when a script resumes its execution.
    JSContext* cx = TlsContext.get();
    for (ActivationIterator iter(cx); !iter.done(); ++iter) {
      if (iter->isInterpreter()) {
        iter->asInterpreter()->enableInterruptsUnconditionally();
      }
    }
    runtime_->incrementNumDebuggeeRealmsObservingCoverage();
    return;
  }

  runtime_->decrementNumDebuggeeRealmsObservingCoverage();

  // If code coverage is enabled by any other means, keep it.
  if (collectCoverageForDebug()) {
    return;
  }

  clearScriptCounts();
  clearScriptLCov();
}

coverage::LCovRealm* Realm::lcovRealm() {
  if (!lcovRealm_) {
    lcovRealm_ = js::MakeUnique<coverage::LCovRealm>(this);
  }
  return lcovRealm_.get();
}

bool Realm::collectCoverageForDebug() const {
  return debuggerObservesCoverage() || coverage::IsLCovEnabled();
}

void Realm::clearScriptCounts() { zone()->clearScriptCounts(this); }

void Realm::clearScriptLCov() { zone()->clearScriptLCov(this); }

const char* Realm::getLocale() const {
  if (RefPtr<LocaleString> locale = creationOptions_.locale()) {
    return locale->chars();
  }

  return runtime_->getDefaultLocale();
}

void ObjectRealm::addSizeOfExcludingThis(
    mozilla::MallocSizeOf mallocSizeOf, size_t* innerViewsArg,
    size_t* objectMetadataTablesArg,
    size_t* nonSyntacticLexicalEnvironmentsArg) {
  *innerViewsArg += innerViews.sizeOfExcludingThis(mallocSizeOf);

  if (objectMetadataTable) {
    *objectMetadataTablesArg +=
        objectMetadataTable->sizeOfIncludingThis(mallocSizeOf);
  }

  if (auto& map = nonSyntacticLexicalEnvironments_) {
    *nonSyntacticLexicalEnvironmentsArg +=
        map->sizeOfIncludingThis(mallocSizeOf);
  }
}

void Realm::addSizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf,
                                   size_t* realmObject, size_t* realmTables,
                                   size_t* innerViewsArg,
                                   size_t* objectMetadataTablesArg,
                                   size_t* savedStacksSet,
                                   size_t* nonSyntacticLexicalEnvironmentsArg) {
  *realmObject += mallocSizeOf(this);
  wasm.addSizeOfExcludingThis(mallocSizeOf, realmTables);

  objects_.addSizeOfExcludingThis(mallocSizeOf, innerViewsArg,
                                  objectMetadataTablesArg,
                                  nonSyntacticLexicalEnvironmentsArg);

  *savedStacksSet += savedStacks_.sizeOfExcludingThis(mallocSizeOf);
}

bool Realm::shouldCaptureStackForThrow() {
  // Determine whether a stack trace should be captured for throw-statements (or
  // similar) in JS code in this realm. We don't want to do this unconditionally
  // because capturing stacks is slow and some scripts throw a lot of
  // exceptions.
  //
  // Note: this is unrelated to Error.stack! That property is observable from
  // JS code so we can't use these heuristics there. The code here is mostly
  // relevant for uncaught exceptions that are not Error objects.

  // To match other browsers, we always capture a stack trace if the realm is a
  // debuggee (this includes the devtools console being open) or if unlimited
  // stack traces have been enabled for this realm (used in automation).
  if (isDebuggee() || isUnlimitedStacksCapturingEnabled) {
    return true;
  }

  // Also always capture for chrome code. This is code we control and this helps
  // debugging.
  if (principals() &&
      principals() == runtimeFromMainThread()->trustedPrincipals()) {
    return true;
  }

  // Else, capture the stack only for the first N exceptions so that we can
  // still show stack traces for scripts that don't throw a lot of exceptions
  // (if the console is opened later).
  static constexpr uint16_t MaxStacksCapturedForThrow = 50;
  if (numStacksCapturedForThrow_ > MaxStacksCapturedForThrow) {
    return false;
  }
  numStacksCapturedForThrow_++;
  return true;
}

mozilla::HashCodeScrambler Realm::randomHashCodeScrambler() {
  return mozilla::HashCodeScrambler(randomKeyGenerator_.next(),
                                    randomKeyGenerator_.next());
}

void AutoSetNewObjectMetadata::setPendingMetadata() {
  JSObject* obj = cx_->realm()->getAndClearObjectPendingMetadata();
  if (!obj) {
    return;
  }

  MOZ_ASSERT(obj->getClass()->shouldDelayMetadataBuilder());

  if (cx_->isExceptionPending()) {
    return;
  }

  // This function is called from a destructor that often runs upon exit from
  // a function that is returning an unrooted pointer to a Cell. The
  // allocation metadata callback often allocates; if it causes a GC, then the
  // Cell pointer being returned won't be traced or relocated.
  //
  // The only extant callbacks are those internal to SpiderMonkey that
  // capture the JS stack. In fact, we're considering removing general
  // callbacks altogther in bug 1236748. Since it's not running arbitrary
  // code, it's adequate to simply suppress GC while we run the callback.
  gc::AutoSuppressGC autoSuppressGC(cx_);

  (void)SetNewObjectMetadata(cx_, obj);
}

JS_PUBLIC_API void gc::TraceRealm(JSTracer* trc, JS::Realm* realm,
                                  const char* name) {
  // The way GC works with compartments is basically incomprehensible.
  // For Realms, what we want is very simple: each Realm has a strong
  // reference to its GlobalObject, and vice versa.
  //
  // Here we simply trace our side of that edge. During GC,
  // GCRuntime::traceRuntimeCommon() marks all other realm roots, for
  // all realms.
  realm->traceGlobalData(trc);
}

JS_PUBLIC_API JS::Realm* JS::GetCurrentRealmOrNull(JSContext* cx) {
  return cx->realm();
}

JS_PUBLIC_API JS::Realm* JS::GetObjectRealmOrNull(JSObject* obj) {
  return IsCrossCompartmentWrapper(obj) ? nullptr : obj->nonCCWRealm();
}

JS_PUBLIC_API void* JS::GetRealmPrivate(JS::Realm* realm) {
  return realm->realmPrivate();
}

JS_PUBLIC_API void JS::SetRealmPrivate(JS::Realm* realm, void* data) {
  realm->setRealmPrivate(data);
}

JS_PUBLIC_API void JS::SetDestroyRealmCallback(
    JSContext* cx, JS::DestroyRealmCallback callback) {
  cx->runtime()->destroyRealmCallback = callback;
}

JS_PUBLIC_API void JS::SetRealmNameCallback(JSContext* cx,
                                            JS::RealmNameCallback callback) {
  cx->runtime()->realmNameCallback = callback;
}

JS_PUBLIC_API JSObject* JS::GetRealmGlobalOrNull(JS::Realm* realm) {
  return realm->maybeGlobal();
}

JS_PUBLIC_API bool JS::InitRealmStandardClasses(JSContext* cx) {
  MOZ_ASSERT(!cx->zone()->isAtomsZone());
  AssertHeapIsIdle();
  CHECK_THREAD(cx);
  return GlobalObject::initStandardClasses(cx, cx->global());
}

JS_PUBLIC_API bool JS::MaybeFreezeCtorAndPrototype(JSContext* cx,
                                                   HandleObject ctor,
                                                   HandleObject maybeProto) {
  if (MOZ_LIKELY(!cx->realm()->creationOptions().freezeBuiltins())) {
    return true;
  }
  if (!SetIntegrityLevel(cx, ctor, IntegrityLevel::Frozen)) {
    return false;
  }
  if (maybeProto) {
    if (!SetIntegrityLevel(cx, maybeProto, IntegrityLevel::Sealed)) {
      return false;
    }
  }
  return true;
}

JS_PUBLIC_API JSObject* JS::GetRealmObjectPrototype(JSContext* cx) {
  CHECK_THREAD(cx);
  return &cx->global()->getObjectPrototype();
}

JS_PUBLIC_API JS::Handle<JSObject*> JS::GetRealmObjectPrototypeHandle(
    JSContext* cx) {
  return cx->global()->getObjectPrototypeHandle();
}

JS_PUBLIC_API JSObject* JS::GetRealmFunctionPrototype(JSContext* cx) {
  CHECK_THREAD(cx);
  return &cx->global()->getFunctionPrototype();
}

JS_PUBLIC_API JSObject* JS::GetRealmArrayPrototype(JSContext* cx) {
  CHECK_THREAD(cx);
  return GlobalObject::getOrCreateArrayPrototype(cx, cx->global());
}

JS_PUBLIC_API JSObject* JS::GetRealmErrorPrototype(JSContext* cx) {
  CHECK_THREAD(cx);
  return GlobalObject::getOrCreateCustomErrorPrototype(cx, cx->global(),
                                                       JSEXN_ERR);
}

JS_PUBLIC_API JSObject* JS::GetRealmIteratorPrototype(JSContext* cx) {
  CHECK_THREAD(cx);
  return GlobalObject::getOrCreateIteratorPrototype(cx, cx->global());
}

JS_PUBLIC_API JSObject* JS::GetRealmAsyncIteratorPrototype(JSContext* cx) {
  CHECK_THREAD(cx);
  return GlobalObject::getOrCreateAsyncIteratorPrototype(cx, cx->global());
}

JS_PUBLIC_API JSObject* JS::GetRealmKeyObject(JSContext* cx) {
  return GlobalObject::getOrCreateRealmKeyObject(cx, cx->global());
}

JS_PUBLIC_API Realm* JS::GetFunctionRealm(JSContext* cx, HandleObject objArg) {
  // https://tc39.github.io/ecma262/#sec-getfunctionrealm
  // 7.3.22 GetFunctionRealm ( obj )

  CHECK_THREAD(cx);
  cx->check(objArg);

  RootedObject obj(cx, objArg);
  while (true) {
    obj = CheckedUnwrapStatic(obj);
    if (!obj) {
      ReportAccessDenied(cx);
      return nullptr;
    }

    // Step 1.
    MOZ_ASSERT(IsCallable(obj));

    // Steps 2 and 3. We use a loop instead of recursion to unwrap bound
    // functions.
    if (obj->is<JSFunction>()) {
      return obj->as<JSFunction>().realm();
    }
    if (obj->is<BoundFunctionObject>()) {
      obj = obj->as<BoundFunctionObject>().getTarget();
      continue;
    }

    // WrappedFunctionObjects also have a [[Realm]] internal slot,
    // which is the nonCCWRealm by construction.
    if (obj->is<WrappedFunctionObject>()) {
      return obj->nonCCWRealm();
    }

    // Step 4.
    if (IsScriptedProxy(obj)) {
      // Steps 4.a-b.
      JSObject* proxyTarget = GetProxyTargetObject(obj);
      if (!proxyTarget) {
        JS_ReportErrorNumberASCII(cx, GetErrorMessage, nullptr,
                                  JSMSG_PROXY_REVOKED);
        return nullptr;
      }

      // Step 4.c.
      obj = proxyTarget;
      continue;
    }

    // Step 5.
    return cx->realm();
  }
}