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 // Copyright 2021 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef INCLUDE_V8_ISOLATE_H_
 #define INCLUDE_V8_ISOLATE_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
 #include <memory>
 #include <string>
 #include <utility>
 
 #include "cppgc/common.h"
 #include "v8-array-buffer.h"       // NOLINT(build/include_directory)
 #include "v8-callbacks.h"          // NOLINT(build/include_directory)
 #include "v8-data.h"               // NOLINT(build/include_directory)
 #include "v8-debug.h"              // NOLINT(build/include_directory)
 #include "v8-embedder-heap.h"      // NOLINT(build/include_directory)
 #include "v8-exception.h"          // NOLINT(build/include_directory)
 #include "v8-function-callback.h"  // NOLINT(build/include_directory)
 #include "v8-internal.h"           // NOLINT(build/include_directory)
 #include "v8-local-handle.h"       // NOLINT(build/include_directory)
 #include "v8-microtask.h"          // NOLINT(build/include_directory)
 #include "v8-persistent-handle.h"  // NOLINT(build/include_directory)
 #include "v8-primitive.h"          // NOLINT(build/include_directory)
 #include "v8-statistics.h"         // NOLINT(build/include_directory)
 #include "v8-unwinder.h"           // NOLINT(build/include_directory)
 #include "v8config.h"              // NOLINT(build/include_directory)
 
 namespace v8 {
 
 class CppHeap;
 class HeapProfiler;
 class MicrotaskQueue;
 class StartupData;
 class ScriptOrModule;
 class SharedArrayBuffer;
 
 namespace internal {
 class MicrotaskQueue;
 class ThreadLocalTop;
 }  // namespace internal
 
 namespace metrics {
 class Recorder;
 }  // namespace metrics
 
 /**
  * A set of constraints that specifies the limits of the runtime's memory use.
  * You must set the heap size before initializing the VM - the size cannot be
  * adjusted after the VM is initialized.
  *
  * If you are using threads then you should hold the V8::Locker lock while
  * setting the stack limit and you must set a non-default stack limit separately
  * for each thread.
  *
  * The arguments for set_max_semi_space_size, set_max_old_space_size,
  * set_max_executable_size, set_code_range_size specify limits in MB.
  *
  * The argument for set_max_semi_space_size_in_kb is in KB.
  */
 class V8_EXPORT ResourceConstraints {
  public:
   /**
    * Configures the constraints with reasonable default values based on the
    * provided heap size limit. The heap size includes both the young and
    * the old generation.
    *
    * \param initial_heap_size_in_bytes The initial heap size or zero.
    *    By default V8 starts with a small heap and dynamically grows it to
    *    match the set of live objects. This may lead to ineffective
    *    garbage collections at startup if the live set is large.
    *    Setting the initial heap size avoids such garbage collections.
    *    Note that this does not affect young generation garbage collections.
    *
    * \param maximum_heap_size_in_bytes The hard limit for the heap size.
    *    When the heap size approaches this limit, V8 will perform series of
    *    garbage collections and invoke the NearHeapLimitCallback. If the garbage
    *    collections do not help and the callback does not increase the limit,
    *    then V8 will crash with V8::FatalProcessOutOfMemory.
    */
   void ConfigureDefaultsFromHeapSize(size_t initial_heap_size_in_bytes,
                                      size_t maximum_heap_size_in_bytes);
 
   /**
    * Configures the constraints with reasonable default values based on the
    * capabilities of the current device the VM is running on.
    *
    * \param physical_memory The total amount of physical memory on the current
    *   device, in bytes.
    * \param virtual_memory_limit The amount of virtual memory on the current
    *   device, in bytes, or zero, if there is no limit.
    */
   void ConfigureDefaults(uint64_t physical_memory,
                          uint64_t virtual_memory_limit);
 
   /**
    * The address beyond which the VM's stack may not grow.
    */
   uint32_t* stack_limit() const { return stack_limit_; }
   void set_stack_limit(uint32_t* value) { stack_limit_ = value; }
 
   /**
    * The amount of virtual memory reserved for generated code. This is relevant
    * for 64-bit architectures that rely on code range for calls in code.
    *
    * When V8_COMPRESS_POINTERS_IN_SHARED_CAGE is defined, there is a shared
    * process-wide code range that is lazily initialized. This value is used to
    * configure that shared code range when the first Isolate is
    * created. Subsequent Isolates ignore this value.
    */
   size_t code_range_size_in_bytes() const { return code_range_size_; }
   void set_code_range_size_in_bytes(size_t limit) { code_range_size_ = limit; }
 
   /**
    * The maximum size of the old generation.
    * When the old generation approaches this limit, V8 will perform series of
    * garbage collections and invoke the NearHeapLimitCallback.
    * If the garbage collections do not help and the callback does not
    * increase the limit, then V8 will crash with V8::FatalProcessOutOfMemory.
    */
   size_t max_old_generation_size_in_bytes() const {
     return max_old_generation_size_;
   }
   void set_max_old_generation_size_in_bytes(size_t limit) {
     max_old_generation_size_ = limit;
   }
 
   /**
    * The maximum size of the young generation, which consists of two semi-spaces
    * and a large object space. This affects frequency of Scavenge garbage
    * collections and should be typically much smaller that the old generation.
    */
   size_t max_young_generation_size_in_bytes() const {
     return max_young_generation_size_;
   }
   void set_max_young_generation_size_in_bytes(size_t limit) {
     max_young_generation_size_ = limit;
   }
 
   size_t initial_old_generation_size_in_bytes() const {
     return initial_old_generation_size_;
   }
   void set_initial_old_generation_size_in_bytes(size_t initial_size) {
     initial_old_generation_size_ = initial_size;
   }
 
   size_t initial_young_generation_size_in_bytes() const {
     return initial_young_generation_size_;
   }
   void set_initial_young_generation_size_in_bytes(size_t initial_size) {
     initial_young_generation_size_ = initial_size;
   }
 
  private:
   static constexpr size_t kMB = 1048576u;
   size_t code_range_size_ = 0;
   size_t max_old_generation_size_ = 0;
   size_t max_young_generation_size_ = 0;
   size_t initial_old_generation_size_ = 0;
   size_t initial_young_generation_size_ = 0;
   uint32_t* stack_limit_ = nullptr;
 };
 
 /**
  * Memory pressure level for the MemoryPressureNotification.
  * kNone hints V8 that there is no memory pressure.
  * kModerate hints V8 to speed up incremental garbage collection at the cost of
  * of higher latency due to garbage collection pauses.
  * kCritical hints V8 to free memory as soon as possible. Garbage collection
  * pauses at this level will be large.
  */
 enum class MemoryPressureLevel { kNone, kModerate, kCritical };
 
 /**
  * Signal for dependants of contexts. Useful for
  * `ContextDisposedNotification()` to implement different strategies.
  */
 enum class ContextDependants {
   /** Context has no dependants. These are usually top-level contexts. */
   kNoDependants,
   /** Context has some dependants, i.e., it may depend on other contexts. This
      is usually the case for inner contexts.  */
   kSomeDependants
 };
 
 /**
  * Indicator for the stack state.
  */
 using StackState = cppgc::EmbedderStackState;
 
 /**
  * The set of V8 isolates in a process is partitioned into groups. Each group
  * has its own sandbox (if V8 was configured with support for the sandbox) and
  * pointer-compression cage (if configured with pointer compression).
  *
  * By default, all isolates are placed in the same group. This is the most
  * efficient configuration in terms of speed and memory use. However, with
  * pointer compression enabled, total heap usage of isolates in a group
  * cannot exceed 4 GB, not counting array buffers and other off-heap storage.
  * Using multiple isolate groups can allow embedders to allocate more than 4GB
  * of objects with pointer compression enabled, if the embedder's use case can
  * span multiple isolates.
  *
  * Creating an isolate group reserves a range of virtual memory addresses. A
  * group's memory mapping will be released when the last isolate in the group is
  * disposed, and there are no more live IsolateGroup objects that refer to it.
  *
  * Note that Isolate groups are reference counted, and
  * the IsolateGroup type is a reference to one.
  *
  * Note that it's not going to be possible to pass shared JS objects
  * across IsolateGroup boundary.
  *
  */
 class V8_EXPORT IsolateGroup {
  public:
   /**
    * Get the default isolate group. If this V8's build configuration only
    * supports a single group, this is a reference to that single group.
    * Otherwise this is a group like any other, distinguished only
    * in that it is the first group.
    */
   static IsolateGroup GetDefault();
 
   /**
    * Return true if new isolate groups can be created at run-time, or false if
    * all isolates must be in the same group.
    */
   static bool CanCreateNewGroups();
 
   /**
    * Create a new isolate group. If this V8's build configuration only supports
    * a single group, abort.
    */
   static IsolateGroup Create();
 
   IsolateGroup(IsolateGroup&& other);
   IsolateGroup& operator=(IsolateGroup&& other);
 
   IsolateGroup(const IsolateGroup&);
   IsolateGroup& operator=(const IsolateGroup&);
 
   ~IsolateGroup();
 
   bool operator==(const IsolateGroup& other) const {
     return isolate_group_ == other.isolate_group_;
   }
 
   bool operator!=(const IsolateGroup& other) const {
     return !operator==(other);
   }
 
  private:
   friend class Isolate;
   friend class ArrayBuffer::Allocator;
 
   // The isolate_group pointer should be already acquired.
   explicit IsolateGroup(internal::IsolateGroup*&& isolate_group);
 
   internal::IsolateGroup* isolate_group_;
 };
 
 /**
  * Isolate represents an isolated instance of the V8 engine.  V8 isolates have
  * completely separate states.  Objects from one isolate must not be used in
  * other isolates.  The embedder can create multiple isolates and use them in
  * parallel in multiple threads.  An isolate can be entered by at most one
  * thread at any given time.  The Locker/Unlocker API must be used to
  * synchronize.
  */
 class V8_EXPORT Isolate {
  public:
   /**
    * Initial configuration parameters for a new Isolate.
    */
   struct V8_EXPORT CreateParams {
     CreateParams();
     ~CreateParams();
 
     ALLOW_COPY_AND_MOVE_WITH_DEPRECATED_FIELDS(CreateParams)
 
     /**
      * Allows the host application to provide the address of a function that is
      * notified each time code is added, moved or removed.
      */
     JitCodeEventHandler code_event_handler = nullptr;
 
     /**
      * ResourceConstraints to use for the new Isolate.
      */
     ResourceConstraints constraints;
 
     /**
      * Explicitly specify a startup snapshot blob. The embedder owns the blob.
      * The embedder *must* ensure that the snapshot is from a trusted source.
      */
     const StartupData* snapshot_blob = nullptr;
 
     /**
      * Enables the host application to provide a mechanism for recording
      * statistics counters.
      */
     CounterLookupCallback counter_lookup_callback = nullptr;
 
     /**
      * Enables the host application to provide a mechanism for recording
      * histograms. The CreateHistogram function returns a
      * histogram which will later be passed to the AddHistogramSample
      * function.
      */
     CreateHistogramCallback create_histogram_callback = nullptr;
     AddHistogramSampleCallback add_histogram_sample_callback = nullptr;
 
     /**
      * The ArrayBuffer::Allocator to use for allocating and freeing the backing
      * store of ArrayBuffers.
      *
      * If the shared_ptr version is used, the Isolate instance and every
      * |BackingStore| allocated using this allocator hold a std::shared_ptr
      * to the allocator, in order to facilitate lifetime
      * management for the allocator instance.
      */
     ArrayBuffer::Allocator* array_buffer_allocator = nullptr;
     std::shared_ptr<ArrayBuffer::Allocator> array_buffer_allocator_shared;
 
     /**
      * Specifies an optional nullptr-terminated array of raw addresses in the
      * embedder that V8 can match against during serialization and use for
      * deserialization. This array and its content must stay valid for the
      * entire lifetime of the isolate.
      */
     const intptr_t* external_references = nullptr;
 
     /**
      * Whether calling Atomics.wait (a function that may block) is allowed in
      * this isolate. This can also be configured via SetAllowAtomicsWait.
      */
     bool allow_atomics_wait = true;
 
     /**
      * The following parameters describe the offsets for addressing type info
      * for wrapped API objects and are used by the fast C API
      * (for details see v8-fast-api-calls.h).
      */
     int embedder_wrapper_type_index = -1;
     int embedder_wrapper_object_index = -1;
 
     /**
      * Callbacks to invoke in case of fatal or OOM errors.
      */
     FatalErrorCallback fatal_error_callback = nullptr;
     OOMErrorCallback oom_error_callback = nullptr;
 
     /**
      * A CppHeap used to construct the Isolate. V8 takes ownership of the
      * CppHeap passed this way.
      */
     CppHeap* cpp_heap = nullptr;
   };
 
   /**
    * Stack-allocated class which sets the isolate for all operations
    * executed within a local scope.
    */
   class V8_EXPORT V8_NODISCARD Scope {
    public:
     explicit Scope(Isolate* isolate) : v8_isolate_(isolate) {
       v8_isolate_->Enter();
     }
 
     ~Scope() { v8_isolate_->Exit(); }
 
     // Prevent copying of Scope objects.
     Scope(const Scope&) = delete;
     Scope& operator=(const Scope&) = delete;
 
    private:
     Isolate* const v8_isolate_;
   };
 
   /**
    * Assert that no Javascript code is invoked.
    */
   class V8_EXPORT V8_NODISCARD DisallowJavascriptExecutionScope {
    public:
     enum OnFailure { CRASH_ON_FAILURE, THROW_ON_FAILURE, DUMP_ON_FAILURE };
 
     DisallowJavascriptExecutionScope(Isolate* isolate, OnFailure on_failure);
     ~DisallowJavascriptExecutionScope();
 
     // Prevent copying of Scope objects.
     DisallowJavascriptExecutionScope(const DisallowJavascriptExecutionScope&) =
         delete;
     DisallowJavascriptExecutionScope& operator=(
         const DisallowJavascriptExecutionScope&) = delete;
 
    private:
     v8::Isolate* const v8_isolate_;
     const OnFailure on_failure_;
     bool was_execution_allowed_;
   };
 
   /**
    * Introduce exception to DisallowJavascriptExecutionScope.
    */
   class V8_EXPORT V8_NODISCARD AllowJavascriptExecutionScope {
    public:
     explicit AllowJavascriptExecutionScope(Isolate* isolate);
     ~AllowJavascriptExecutionScope();
 
     // Prevent copying of Scope objects.
     AllowJavascriptExecutionScope(const AllowJavascriptExecutionScope&) =
         delete;
     AllowJavascriptExecutionScope& operator=(
         const AllowJavascriptExecutionScope&) = delete;
 
    private:
     Isolate* const v8_isolate_;
     bool was_execution_allowed_assert_;
     bool was_execution_allowed_throws_;
     bool was_execution_allowed_dump_;
   };
 
   /**
    * Do not run microtasks while this scope is active, even if microtasks are
    * automatically executed otherwise.
    */
   class V8_EXPORT V8_NODISCARD SuppressMicrotaskExecutionScope {
    public:
     explicit SuppressMicrotaskExecutionScope(
         Isolate* isolate, MicrotaskQueue* microtask_queue = nullptr);
     ~SuppressMicrotaskExecutionScope();
 
     // Prevent copying of Scope objects.
     SuppressMicrotaskExecutionScope(const SuppressMicrotaskExecutionScope&) =
         delete;
     SuppressMicrotaskExecutionScope& operator=(
         const SuppressMicrotaskExecutionScope&) = delete;
 
    private:
     internal::Isolate* const i_isolate_;
     internal::MicrotaskQueue* const microtask_queue_;
     internal::Address previous_stack_height_;
 
     friend class internal::ThreadLocalTop;
   };
 
   /**
    * Types of garbage collections that can be requested via
    * RequestGarbageCollectionForTesting.
    */
   enum GarbageCollectionType {
     kFullGarbageCollection,
     kMinorGarbageCollection
   };
 
   /**
    * Features reported via the SetUseCounterCallback callback. Do not change
    * assigned numbers of existing items; add new features to the end of this
    * list.
    * Dead features can be marked `V8_DEPRECATE_SOON`, then `V8_DEPRECATED`, and
    * then finally be renamed to `kOBSOLETE_...` to stop embedders from using
    * them.
    */
   enum UseCounterFeature {
     kUseAsm = 0,
     kBreakIterator = 1,
     kOBSOLETE_LegacyConst = 2,
     kOBSOLETE_MarkDequeOverflow = 3,
     kOBSOLETE_StoreBufferOverflow = 4,
     kOBSOLETE_SlotsBufferOverflow = 5,
     kOBSOLETE_ObjectObserve = 6,
     kForcedGC = 7,
     kSloppyMode = 8,
     kStrictMode = 9,
     kOBSOLETE_StrongMode = 10,
     kRegExpPrototypeStickyGetter = 11,
     kRegExpPrototypeToString = 12,
     kRegExpPrototypeUnicodeGetter = 13,
     kOBSOLETE_IntlV8Parse = 14,
     kOBSOLETE_IntlPattern = 15,
     kOBSOLETE_IntlResolved = 16,
     kOBSOLETE_PromiseChain = 17,
     kOBSOLETE_PromiseAccept = 18,
     kOBSOLETE_PromiseDefer = 19,
     kHtmlCommentInExternalScript = 20,
     kHtmlComment = 21,
     kSloppyModeBlockScopedFunctionRedefinition = 22,
     kForInInitializer = 23,
     kOBSOLETE_ArrayProtectorDirtied = 24,
     kArraySpeciesModified = 25,
     kArrayPrototypeConstructorModified = 26,
     kOBSOLETE_ArrayInstanceProtoModified = 27,
     kArrayInstanceConstructorModified = 28,
     kOBSOLETE_LegacyFunctionDeclaration = 29,
     kOBSOLETE_RegExpPrototypeSourceGetter = 30,
     kOBSOLETE_RegExpPrototypeOldFlagGetter = 31,
     kDecimalWithLeadingZeroInStrictMode = 32,
     kLegacyDateParser = 33,
     kDefineGetterOrSetterWouldThrow = 34,
     kFunctionConstructorReturnedUndefined = 35,
     kAssigmentExpressionLHSIsCallInSloppy = 36,
     kAssigmentExpressionLHSIsCallInStrict = 37,
     kPromiseConstructorReturnedUndefined = 38,
     kOBSOLETE_ConstructorNonUndefinedPrimitiveReturn = 39,
     kOBSOLETE_LabeledExpressionStatement = 40,
     kOBSOLETE_LineOrParagraphSeparatorAsLineTerminator = 41,
     kIndexAccessor = 42,
     kErrorCaptureStackTrace = 43,
     kErrorPrepareStackTrace = 44,
     kErrorStackTraceLimit = 45,
     kWebAssemblyInstantiation = 46,
     kDeoptimizerDisableSpeculation = 47,
     kOBSOLETE_ArrayPrototypeSortJSArrayModifiedPrototype = 48,
     kFunctionTokenOffsetTooLongForToString = 49,
     kWasmSharedMemory = 50,
     kWasmThreadOpcodes = 51,
     kOBSOLETE_AtomicsNotify = 52,
     kOBSOLETE_AtomicsWake = 53,
     kCollator = 54,
     kNumberFormat = 55,
     kDateTimeFormat = 56,
     kPluralRules = 57,
     kRelativeTimeFormat = 58,
     kLocale = 59,
     kListFormat = 60,
     kSegmenter = 61,
     kStringLocaleCompare = 62,
     kOBSOLETE_StringToLocaleUpperCase = 63,
     kStringToLocaleLowerCase = 64,
     kNumberToLocaleString = 65,
     kDateToLocaleString = 66,
     kDateToLocaleDateString = 67,
     kDateToLocaleTimeString = 68,
     kAttemptOverrideReadOnlyOnPrototypeSloppy = 69,
     kAttemptOverrideReadOnlyOnPrototypeStrict = 70,
     kOBSOLETE_OptimizedFunctionWithOneShotBytecode = 71,
     kRegExpMatchIsTrueishOnNonJSRegExp = 72,
     kRegExpMatchIsFalseishOnJSRegExp = 73,
     kOBSOLETE_DateGetTimezoneOffset = 74,
     kStringNormalize = 75,
     kCallSiteAPIGetFunctionSloppyCall = 76,
     kCallSiteAPIGetThisSloppyCall = 77,
     kOBSOLETE_RegExpMatchAllWithNonGlobalRegExp = 78,
     kRegExpExecCalledOnSlowRegExp = 79,
     kRegExpReplaceCalledOnSlowRegExp = 80,
     kDisplayNames = 81,
     kSharedArrayBufferConstructed = 82,
     kArrayPrototypeHasElements = 83,
     kObjectPrototypeHasElements = 84,
     kNumberFormatStyleUnit = 85,
     kDateTimeFormatRange = 86,
     kDateTimeFormatDateTimeStyle = 87,
     kBreakIteratorTypeWord = 88,
     kBreakIteratorTypeLine = 89,
     kInvalidatedArrayBufferDetachingProtector = 90,
     kInvalidatedArrayConstructorProtector = 91,
     kInvalidatedArrayIteratorLookupChainProtector = 92,
     kInvalidatedArraySpeciesLookupChainProtector = 93,
     kInvalidatedIsConcatSpreadableLookupChainProtector = 94,
     kInvalidatedMapIteratorLookupChainProtector = 95,
     kInvalidatedNoElementsProtector = 96,
     kInvalidatedPromiseHookProtector = 97,
     kInvalidatedPromiseResolveLookupChainProtector = 98,
     kInvalidatedPromiseSpeciesLookupChainProtector = 99,
     kInvalidatedPromiseThenLookupChainProtector = 100,
     kInvalidatedRegExpSpeciesLookupChainProtector = 101,
     kInvalidatedSetIteratorLookupChainProtector = 102,
     kInvalidatedStringIteratorLookupChainProtector = 103,
     kInvalidatedStringLengthOverflowLookupChainProtector = 104,
     kInvalidatedTypedArraySpeciesLookupChainProtector = 105,
     kWasmSimdOpcodes = 106,
     kVarRedeclaredCatchBinding = 107,
     kWasmRefTypes = 108,
     kOBSOLETE_WasmBulkMemory = 109,
     kOBSOLETE_WasmMultiValue = 110,
     kWasmExceptionHandling = 111,
     kInvalidatedMegaDOMProtector = 112,
     kFunctionPrototypeArguments = 113,
     kFunctionPrototypeCaller = 114,
     kTurboFanOsrCompileStarted = 115,
     kAsyncStackTaggingCreateTaskCall = 116,
     kDurationFormat = 117,
     kInvalidatedNumberStringNotRegexpLikeProtector = 118,
     kOBSOLETE_RegExpUnicodeSetIncompatibilitiesWithUnicodeMode = 119,
     kOBSOLETE_ImportAssertionDeprecatedSyntax = 120,
     kLocaleInfoObsoletedGetters = 121,
     kLocaleInfoFunctions = 122,
     kCompileHintsMagicAll = 123,
     kInvalidatedNoProfilingProtector = 124,
     kWasmMemory64 = 125,
     kWasmMultiMemory = 126,
     kWasmGC = 127,
     kWasmImportedStrings = 128,
     kSourceMappingUrlMagicCommentAtSign = 129,
     kTemporalObject = 130,
     kWasmModuleCompilation = 131,
     kInvalidatedNoUndetectableObjectsProtector = 132,
     kWasmJavaScriptPromiseIntegration = 133,
     kWasmReturnCall = 134,
     kWasmExtendedConst = 135,
     kWasmRelaxedSimd = 136,
     kWasmTypeReflection = 137,
     kWasmExnRef = 138,
     kWasmTypedFuncRef = 139,
     kInvalidatedStringWrapperToPrimitiveProtector = 140,
     kDocumentAllLegacyCall = 141,
     kDocumentAllLegacyConstruct = 142,
     kConsoleContext = 143,
     kWasmImportedStringsUtf8 = 144,
     kResizableArrayBuffer = 145,
     kGrowableSharedArrayBuffer = 146,
     kArrayByCopy = 147,
     kArrayFromAsync = 148,
     kIteratorMethods = 149,
     kPromiseAny = 150,
     kSetMethods = 151,
     kArrayFindLast = 152,
     kArrayGroup = 153,
     kArrayBufferTransfer = 154,
     kPromiseWithResolvers = 155,
     kAtomicsWaitAsync = 156,
     kExtendingNonExtensibleWithPrivate = 157,
     kPromiseTry = 158,
     kStringReplaceAll = 159,
     kStringWellFormed = 160,
     kWeakReferences = 161,
     kErrorIsError = 162,
     kInvalidatedTypedArrayLengthLookupChainProtector = 163,
     kRegExpEscape = 164,
     kFloat16Array = 165,
     kExplicitResourceManagement = 166,
     kWasmBranchHinting = 167,
 
     // If you add new values here, you'll also need to update Chromium's:
     // web_feature.mojom, use_counter_callback.cc, and enums.xml. V8 changes to
     // this list need to be landed first, then changes on the Chromium side.
     kUseCounterFeatureCount  // This enum value must be last.
   };
 
   enum MessageErrorLevel {
     kMessageLog = (1 << 0),
     kMessageDebug = (1 << 1),
     kMessageInfo = (1 << 2),
     kMessageError = (1 << 3),
     kMessageWarning = (1 << 4),
     kMessageAll = kMessageLog | kMessageDebug | kMessageInfo | kMessageError |
                   kMessageWarning,
   };
 
   // The different priorities that an isolate can have.
   enum class Priority {
     // The isolate does not relate to content that is currently important
     // to the user. Lowest priority.
     kBestEffort,
 
     // The isolate contributes to content that is visible to the user, like a
     // visible iframe that's not interacted directly with. High priority.
     kUserVisible,
 
     // The isolate contributes to content that is of the utmost importance to
     // the user, like visible content in the focused window. Highest priority.
     kUserBlocking,
   };
 
   using UseCounterCallback = void (*)(Isolate* isolate,
                                       UseCounterFeature feature);
 
   /**
    * Allocates a new isolate but does not initialize it. Does not change the
    * currently entered isolate.
    *
    * Only Isolate::GetData() and Isolate::SetData(), which access the
    * embedder-controlled parts of the isolate, as well as Isolate::GetGroup(),
    * are allowed to be called on the uninitialized isolate. To initialize the
    * isolate, call `Isolate::Initialize()` or initialize a `SnapshotCreator`.
    *
    * When an isolate is no longer used its resources should be freed
    * by calling Dispose().  Using the delete operator is not allowed.
    *
    * V8::Initialize() must have run prior to this.
    */
   static Isolate* Allocate();
   static Isolate* Allocate(const IsolateGroup& group);
 
   /**
    * Return the group for this isolate.
    */
   IsolateGroup GetGroup() const;
 
   /**
    * Initialize an Isolate previously allocated by Isolate::Allocate().
    */
   static void Initialize(Isolate* isolate, const CreateParams& params);
 
   /**
    * Creates a new isolate.  Does not change the currently entered
    * isolate.
    *
    * When an isolate is no longer used its resources should be freed
    * by calling Dispose().  Using the delete operator is not allowed.
    *
    * V8::Initialize() must have run prior to this.
    */
   static Isolate* New(const CreateParams& params);
   static Isolate* New(const IsolateGroup& group, const CreateParams& params);
 
   /**
    * Returns the entered isolate for the current thread or NULL in
    * case there is no current isolate.
    *
    * This method must not be invoked before V8::Initialize() was invoked.
    */
   static Isolate* GetCurrent();
 
   /**
    * Returns the entered isolate for the current thread or NULL in
    * case there is no current isolate.
    *
    * No checks are performed by this method.
    */
   static Isolate* TryGetCurrent();
 
   /**
    * Return true if this isolate is currently active.
    **/
   bool IsCurrent() const;
 
   /**
    * Clears the set of objects held strongly by the heap. This set of
    * objects are originally built when a WeakRef is created or
    * successfully dereferenced.
    *
    * This is invoked automatically after microtasks are run. See
    * MicrotasksPolicy for when microtasks are run.
    *
    * This needs to be manually invoked only if the embedder is manually running
    * microtasks via a custom MicrotaskQueue class's PerformCheckpoint. In that
    * case, it is the embedder's responsibility to make this call at a time which
    * does not interrupt synchronous ECMAScript code execution.
    */
   void ClearKeptObjects();
 
   /**
    * Custom callback used by embedders to help V8 determine if it should abort
    * when it throws and no internal handler is predicted to catch the
    * exception. If --abort-on-uncaught-exception is used on the command line,
    * then V8 will abort if either:
    * - no custom callback is set.
    * - the custom callback set returns true.
    * Otherwise, the custom callback will not be called and V8 will not abort.
    */
   using AbortOnUncaughtExceptionCallback = bool (*)(Isolate*);
   void SetAbortOnUncaughtExceptionCallback(
       AbortOnUncaughtExceptionCallback callback);
 
   /**
    * This specifies the callback called by the upcoming dynamic
    * import() language feature to load modules.
    */
   void SetHostImportModuleDynamicallyCallback(
       HostImportModuleDynamicallyCallback callback);
 
   /**
    * This specifies the callback called by the upcoming dynamic
    * import() and import.source() language feature to load modules.
    *
    * This API is experimental and is expected to be changed or removed in the
    * future. The callback is currently only called when for source-phase
    * imports. Evaluation-phase imports use the existing
    * HostImportModuleDynamicallyCallback callback.
    */
   void SetHostImportModuleWithPhaseDynamicallyCallback(
       HostImportModuleWithPhaseDynamicallyCallback callback);
 
   /**
    * This specifies the callback called by the upcoming import.meta
    * language feature to retrieve host-defined meta data for a module.
    */
   void SetHostInitializeImportMetaObjectCallback(
       HostInitializeImportMetaObjectCallback callback);
 
   /**
    * This specifies the callback called by the upcoming ShadowRealm
    * construction language feature to retrieve host created globals.
    */
   void SetHostCreateShadowRealmContextCallback(
       HostCreateShadowRealmContextCallback callback);
 
   /**
    * Set the callback that checks whether a Error.isError should return true for
    * a JSApiWrapper object, i.e. whether it represents a native JS error. For
    * example, in an HTML embedder, DOMExceptions are considered native errors.
    */
   void SetIsJSApiWrapperNativeErrorCallback(
       IsJSApiWrapperNativeErrorCallback callback);
 
   /**
    * This specifies the callback called when the stack property of Error
    * is accessed.
    */
   void SetPrepareStackTraceCallback(PrepareStackTraceCallback callback);
 
   /**
    * Get the stackTraceLimit property of Error.
    */
   int GetStackTraceLimit();
 
 #if defined(V8_OS_WIN)
   /**
    * This specifies the callback called when an ETW tracing session starts.
    */
   V8_DEPRECATE_SOON("Use SetFilterETWSessionByURL2Callback instead")
   void SetFilterETWSessionByURLCallback(FilterETWSessionByURLCallback callback);
   void SetFilterETWSessionByURL2Callback(
       FilterETWSessionByURL2Callback callback);
 #endif  // V8_OS_WIN
 
   /**
    * Optional notification that the system is running low on memory.
    * V8 uses these notifications to guide heuristics.
    * It is allowed to call this function from another thread while
    * the isolate is executing long running JavaScript code.
    */
   void MemoryPressureNotification(MemoryPressureLevel level);
 
   /**
    * Optional request from the embedder to tune v8 towards energy efficiency
    * rather than speed if `battery_saver_mode_enabled` is true, because the
    * embedder is in battery saver mode. If false, the correct tuning is left
    * to v8 to decide.
    */
   void SetBatterySaverMode(bool battery_saver_mode_enabled);
 
   /**
    * Optional request from the embedder to tune v8 towards memory efficiency
    * rather than speed if `memory_saver_mode_enabled` is true, because the
    * embedder is in memory saver mode. If false, the correct tuning is left
    * to v8 to decide.
    */
   void SetMemorySaverMode(bool memory_saver_mode_enabled);
 
   /**
    * Drop non-essential caches. Should only be called from testing code.
    * The method can potentially block for a long time and does not necessarily
    * trigger GC.
    */
   void ClearCachesForTesting();
 
   /**
    * Methods below this point require holding a lock (using Locker) in
    * a multi-threaded environment.
    */
 
   /**
    * Sets this isolate as the entered one for the current thread.
    * Saves the previously entered one (if any), so that it can be
    * restored when exiting.  Re-entering an isolate is allowed.
    */
   void Enter();
 
   /**
    * Exits this isolate by restoring the previously entered one in the
    * current thread.  The isolate may still stay the same, if it was
    * entered more than once.
    *
    * Requires: this == Isolate::GetCurrent().
    */
   void Exit();
 
   /**
    * Deinitializes and frees the isolate. The isolate must not be entered by any
    * thread to be disposable.
    */
   void Dispose();
 
   /**
    * Deinitializes the isolate, but does not free the address. The isolate must
    * not be entered by any thread to be deinitializable. Embedders must call
    * Isolate::Free() to free the isolate afterwards.
    */
   void Deinitialize();
 
   /**
    * Frees the memory allocated for the isolate. Can only be called after the
    * Isolate has already been deinitialized with Isolate::Deinitialize(). After
    * the isolate is freed, the next call to Isolate::New() or
    * Isolate::Allocate() might return the same address that just get freed.
    */
   static void Free(Isolate* isolate);
 
   /**
    * Dumps activated low-level V8 internal stats. This can be used instead
    * of performing a full isolate disposal.
    */
   void DumpAndResetStats();
 
   /**
    * Discards all V8 thread-specific data for the Isolate. Should be used
    * if a thread is terminating and it has used an Isolate that will outlive
    * the thread -- all thread-specific data for an Isolate is discarded when
    * an Isolate is disposed so this call is pointless if an Isolate is about
    * to be Disposed.
    */
   void DiscardThreadSpecificMetadata();
 
   /**
    * Associate embedder-specific data with the isolate. |slot| has to be
    * between 0 and GetNumberOfDataSlots() - 1.
    */
   V8_INLINE void SetData(uint32_t slot, void* data);
 
   /**
    * Retrieve embedder-specific data from the isolate.
    * Returns NULL if SetData has never been called for the given |slot|.
    */
   V8_INLINE void* GetData(uint32_t slot);
 
   /**
    * Returns the maximum number of available embedder data slots. Valid slots
    * are in the range of 0 - GetNumberOfDataSlots() - 1.
    */
   V8_INLINE static uint32_t GetNumberOfDataSlots();
 
   /**
    * Return data that was previously attached to the isolate snapshot via
    * SnapshotCreator, and removes the reference to it.
    * Repeated call with the same index returns an empty MaybeLocal.
    */
   template <class T>
   V8_INLINE MaybeLocal<T> GetDataFromSnapshotOnce(size_t index);
 
   /**
    * Returns the value that was set or restored by
    * SetContinuationPreservedEmbedderData(), if any.
    */
   Local<Value> GetContinuationPreservedEmbedderData();
 
   /**
    * Sets a value that will be stored on continuations and reset while the
    * continuation runs.
    */
   void SetContinuationPreservedEmbedderData(Local<Value> data);
 
   /**
    * Get statistics about the heap memory usage.
    */
   void GetHeapStatistics(HeapStatistics* heap_statistics);
 
   /**
    * Returns the number of spaces in the heap.
    */
   size_t NumberOfHeapSpaces();
 
   /**
    * Get the memory usage of a space in the heap.
    *
    * \param space_statistics The HeapSpaceStatistics object to fill in
    *   statistics.
    * \param index The index of the space to get statistics from, which ranges
    *   from 0 to NumberOfHeapSpaces() - 1.
    * \returns true on success.
    */
   bool GetHeapSpaceStatistics(HeapSpaceStatistics* space_statistics,
                               size_t index);
 
   /**
    * Returns the number of types of objects tracked in the heap at GC.
    */
   size_t NumberOfTrackedHeapObjectTypes();
 
   /**
    * Get statistics about objects in the heap.
    *
    * \param object_statistics The HeapObjectStatistics object to fill in
    *   statistics of objects of given type, which were live in the previous GC.
    * \param type_index The index of the type of object to fill details about,
    *   which ranges from 0 to NumberOfTrackedHeapObjectTypes() - 1.
    * \returns true on success.
    */
   bool GetHeapObjectStatisticsAtLastGC(HeapObjectStatistics* object_statistics,
                                        size_t type_index);
 
   /**
    * Get statistics about code and its metadata in the heap.
    *
    * \param object_statistics The HeapCodeStatistics object to fill in
    *   statistics of code, bytecode and their metadata.
    * \returns true on success.
    */
   bool GetHeapCodeAndMetadataStatistics(HeapCodeStatistics* object_statistics);
 
   /**
    * This API is experimental and may change significantly.
    *
    * Enqueues a memory measurement request and invokes the delegate with the
    * results.
    *
    * \param delegate the delegate that defines which contexts to measure and
    *   reports the results.
    *
    * \param execution promptness executing the memory measurement.
    *   The kEager value is expected to be used only in tests.
    */
   bool MeasureMemory(
       std::unique_ptr<MeasureMemoryDelegate> delegate,
       MeasureMemoryExecution execution = MeasureMemoryExecution::kDefault);
 
   /**
    * Get a call stack sample from the isolate.
    * \param state Execution state.
    * \param frames Caller allocated buffer to store stack frames.
    * \param frames_limit Maximum number of frames to capture. The buffer must
    *                     be large enough to hold the number of frames.
    * \param sample_info The sample info is filled up by the function
    *                    provides number of actual captured stack frames and
    *                    the current VM state.
    * \note GetStackSample should only be called when the JS thread is paused or
    *       interrupted. Otherwise the behavior is undefined.
    */
   void GetStackSample(const RegisterState& state, void** frames,
                       size_t frames_limit, SampleInfo* sample_info);
 
   /**
    * Adjusts the amount of registered external memory.
    *
    * \param change_in_bytes the change in externally allocated memory that is
    *   kept alive by JavaScript objects.
    * \returns the adjusted value.
    */
   V8_DEPRECATE_SOON("Use ExternalMemoryAccounter instead.")
   int64_t AdjustAmountOfExternalAllocatedMemory(int64_t change_in_bytes);
 
   /**
    * Returns heap profiler for this isolate. Will return NULL until the isolate
    * is initialized.
    */
   HeapProfiler* GetHeapProfiler();
 
   /**
    * Tells the VM whether the embedder is idle or not.
    */
   void SetIdle(bool is_idle);
 
   /** Returns the ArrayBuffer::Allocator used in this isolate. */
   ArrayBuffer::Allocator* GetArrayBufferAllocator();
 
   /** Returns true if this isolate has a current context. */
   bool InContext();
 
   /**
    * Returns the context of the currently running JavaScript, or the context
    * on the top of the stack if no JavaScript is running.
    */
   Local<Context> GetCurrentContext();
 
   /**
    * Returns either the last context entered through V8's C++ API, or the
    * context of the currently running microtask while processing microtasks.
    * If a context is entered while executing a microtask, that context is
    * returned.
    */
   Local<Context> GetEnteredOrMicrotaskContext();
 
   /**
    * Returns the Context that corresponds to the Incumbent realm in HTML spec.
    * https://html.spec.whatwg.org/multipage/webappapis.html#incumbent
    */
   Local<Context> GetIncumbentContext();
 
   /**
    * Returns the host defined options set for currently running script or
    * module, if available.
    */
   MaybeLocal<Data> GetCurrentHostDefinedOptions();
 
   /**
    * Schedules a v8::Exception::Error with the given message.
    * See ThrowException for more details. Templatized to provide compile-time
    * errors in case of too long strings (see v8::String::NewFromUtf8Literal).
    */
   template <int N>
   Local<Value> ThrowError(const char (&message)[N]) {
     return ThrowError(String::NewFromUtf8Literal(this, message));
   }
   Local<Value> ThrowError(Local<String> message);
 
   /**
    * Schedules an exception to be thrown when returning to JavaScript.  When an
    * exception has been scheduled it is illegal to invoke any JavaScript
    * operation; the caller must return immediately and only after the exception
    * has been handled does it become legal to invoke JavaScript operations.
    */
   Local<Value> ThrowException(Local<Value> exception);
 
   /**
    * Returns true if an exception was thrown but not processed yet by an
    * exception handler on JavaScript side or by v8::TryCatch handler.
    *
    * This is an experimental feature and may still change significantly.
    */
   bool HasPendingException();
 
   using GCCallback = void (*)(Isolate* isolate, GCType type,
                               GCCallbackFlags flags);
   using GCCallbackWithData = void (*)(Isolate* isolate, GCType type,
                                       GCCallbackFlags flags, void* data);
 
   /**
    * Enables the host application to receive a notification before a
    * garbage collection.
    *
    * \param callback The callback to be invoked. The callback is allowed to
    *     allocate but invocation is not re-entrant: a callback triggering
    *     garbage collection will not be called again. JS execution is prohibited
    *     from these callbacks. A single callback may only be registered once.
    * \param gc_type_filter A filter in case it should be applied.
    */
   void AddGCPrologueCallback(GCCallback callback,
                              GCType gc_type_filter = kGCTypeAll);
 
   /**
    * \copydoc AddGCPrologueCallback(GCCallback, GCType)
    *
    * \param data Additional data that should be passed to the callback.
    */
   void AddGCPrologueCallback(GCCallbackWithData callback, void* data = nullptr,
                              GCType gc_type_filter = kGCTypeAll);
 
   /**
    * This function removes a callback which was added by
    * `AddGCPrologueCallback`.
    *
    * \param callback the callback to remove.
    */
   void RemoveGCPrologueCallback(GCCallback callback);
 
   /**
    * \copydoc AddGCPrologueCallback(GCCallback)
    *
    * \param data Additional data that was used to install the callback.
    */
   void RemoveGCPrologueCallback(GCCallbackWithData, void* data = nullptr);
 
   /**
    * Enables the host application to receive a notification after a
    * garbage collection.
    *
    * \copydetails AddGCPrologueCallback(GCCallback, GCType)
    */
   void AddGCEpilogueCallback(GCCallback callback,
                              GCType gc_type_filter = kGCTypeAll);
 
   /**
    * \copydoc AddGCEpilogueCallback(GCCallback, GCType)
    *
    * \param data Additional data that should be passed to the callback.
    */
   void AddGCEpilogueCallback(GCCallbackWithData callback, void* data = nullptr,
                              GCType gc_type_filter = kGCTypeAll);
 
   /**
    * This function removes a callback which was added by
    * `AddGCEpilogueCallback`.
    *
    * \param callback the callback to remove.
    */
   void RemoveGCEpilogueCallback(GCCallback callback);
 
   /**
    * \copydoc RemoveGCEpilogueCallback(GCCallback)
    *
    * \param data Additional data that was used to install the callback.
    */
   void RemoveGCEpilogueCallback(GCCallbackWithData callback,
                                 void* data = nullptr);
 
   /**
    * Sets an embedder roots handle that V8 should consider when performing
    * non-unified heap garbage collections. The intended use case is for setting
    * a custom handler after invoking `AttachCppHeap()`.
    *
    * V8 does not take ownership of the handler.
    */
   void SetEmbedderRootsHandler(EmbedderRootsHandler* handler);
 
   using ReleaseCppHeapCallback = void (*)(std::unique_ptr<CppHeap>);
 
   /**
    * Sets a callback on the isolate that gets called when the CppHeap gets
    * detached. The callback can then either take ownership of the CppHeap, or
    * the CppHeap gets deallocated.
    */
   void SetReleaseCppHeapCallbackForTesting(ReleaseCppHeapCallback callback);
 
   /**
    * \returns the C++ heap managed by V8. Only available if such a heap has been
    *   attached using `AttachCppHeap()`.
    */
   CppHeap* GetCppHeap() const;
 
   using GetExternallyAllocatedMemoryInBytesCallback = size_t (*)();
 
   /**
    * Set the callback that tells V8 how much memory is currently allocated
    * externally of the V8 heap. Ideally this memory is somehow connected to V8
    * objects and may get freed-up when the corresponding V8 objects get
    * collected by a V8 garbage collection.
    */
   void SetGetExternallyAllocatedMemoryInBytesCallback(
       GetExternallyAllocatedMemoryInBytesCallback callback);
 
   /**
    * Forcefully terminate the current thread of JavaScript execution
    * in the given isolate.
    *
    * This method can be used by any thread even if that thread has not
    * acquired the V8 lock with a Locker object.
    */
   void TerminateExecution();
 
   /**
    * Is V8 terminating JavaScript execution.
    *
    * Returns true if JavaScript execution is currently terminating
    * because of a call to TerminateExecution.  In that case there are
    * still JavaScript frames on the stack and the termination
    * exception is still active.
    */
   bool IsExecutionTerminating();
 
   /**
    * Resume execution capability in the given isolate, whose execution
    * was previously forcefully terminated using TerminateExecution().
    *
    * When execution is forcefully terminated using TerminateExecution(),
    * the isolate can not resume execution until all JavaScript frames
    * have propagated the uncatchable exception which is generated.  This
    * method allows the program embedding the engine to handle the
    * termination event and resume execution capability, even if
    * JavaScript frames remain on the stack.
    *
    * This method can be used by any thread even if that thread has not
    * acquired the V8 lock with a Locker object.
    */
   void CancelTerminateExecution();
 
   /**
    * Request V8 to interrupt long running JavaScript code and invoke
    * the given |callback| passing the given |data| to it. After |callback|
    * returns control will be returned to the JavaScript code.
    * There may be a number of interrupt requests in flight.
    * Can be called from another thread without acquiring a |Locker|.
    * Registered |callback| must not reenter interrupted Isolate.
    */
   void RequestInterrupt(InterruptCallback callback, void* data);
 
   /**
    * Returns true if there is ongoing background work within V8 that will
    * eventually post a foreground task, like asynchronous WebAssembly
    * compilation.
    */
   bool HasPendingBackgroundTasks();
 
   /**
    * Request garbage collection in this Isolate. It is only valid to call this
    * function if --expose_gc was specified.
    *
    * This should only be used for testing purposes and not to enforce a garbage
    * collection schedule. It has strong negative impact on the garbage
    * collection performance. Use MemoryPressureNotification() instead to
    * influence the garbage collection schedule.
    */
   void RequestGarbageCollectionForTesting(GarbageCollectionType type);
 
   /**
    * Request garbage collection with a specific embedderstack state in this
    * Isolate. It is only valid to call this function if --expose_gc was
    * specified.
    *
    * This should only be used for testing purposes and not to enforce a garbage
    * collection schedule. It has strong negative impact on the garbage
    * collection performance. Use MemoryPressureNotification() instead to
    * influence the garbage collection schedule.
    */
   void RequestGarbageCollectionForTesting(GarbageCollectionType type,
                                           StackState stack_state);
 
   /**
    * Set the callback to invoke for logging event.
    */
   void SetEventLogger(LogEventCallback that);
 
   /**
    * Adds a callback to notify the host application right before a script
    * is about to run. If a script re-enters the runtime during executing, the
    * BeforeCallEnteredCallback is invoked for each re-entrance.
    * Executing scripts inside the callback will re-trigger the callback.
    */
   void AddBeforeCallEnteredCallback(BeforeCallEnteredCallback callback);
 
   /**
    * Removes callback that was installed by AddBeforeCallEnteredCallback.
    */
   void RemoveBeforeCallEnteredCallback(BeforeCallEnteredCallback callback);
 
   /**
    * Adds a callback to notify the host application when a script finished
    * running.  If a script re-enters the runtime during executing, the
    * CallCompletedCallback is only invoked when the outer-most script
    * execution ends.  Executing scripts inside the callback do not trigger
    * further callbacks.
    */
   void AddCallCompletedCallback(CallCompletedCallback callback);
 
   /**
    * Removes callback that was installed by AddCallCompletedCallback.
    */
   void RemoveCallCompletedCallback(CallCompletedCallback callback);
 
   /**
    * Set the PromiseHook callback for various promise lifecycle
    * events.
    */
   void SetPromiseHook(PromiseHook hook);
 
   /**
    * Set callback to notify about promise reject with no handler, or
    * revocation of such a previous notification once the handler is added.
    */
   void SetPromiseRejectCallback(PromiseRejectCallback callback);
 
   /**
    * This is a part of experimental Api and might be changed without further
    * notice.
    * Do not use it.
    *
    * Set callback to notify about a new exception being thrown.
    */
   void SetExceptionPropagationCallback(ExceptionPropagationCallback callback);
 
   /**
    * Runs the default MicrotaskQueue until it gets empty and perform other
    * microtask checkpoint steps, such as calling ClearKeptObjects. Asserts that
    * the MicrotasksPolicy is not kScoped. Any exceptions thrown by microtask
    * callbacks are swallowed.
    */
   void PerformMicrotaskCheckpoint();
 
   /**
    * Enqueues the callback to the default MicrotaskQueue
    */
   void EnqueueMicrotask(Local<Function> microtask);
 
   /**
    * Enqueues the callback to the default MicrotaskQueue
    */
   void EnqueueMicrotask(MicrotaskCallback callback, void* data = nullptr);
 
   /**
    * Controls how Microtasks are invoked. See MicrotasksPolicy for details.
    */
   void SetMicrotasksPolicy(MicrotasksPolicy policy);
 
   /**
    * Returns the policy controlling how Microtasks are invoked.
    */
   MicrotasksPolicy GetMicrotasksPolicy() const;
 
   /**
    * Adds a callback to notify the host application after
    * microtasks were run on the default MicrotaskQueue. The callback is
    * triggered by explicit RunMicrotasks call or automatic microtasks execution
    * (see SetMicrotaskPolicy).
    *
    * Callback will trigger even if microtasks were attempted to run,
    * but the microtasks queue was empty and no single microtask was actually
    * executed.
    *
    * Executing scripts inside the callback will not re-trigger microtasks and
    * the callback.
    */
   void AddMicrotasksCompletedCallback(
       MicrotasksCompletedCallbackWithData callback, void* data = nullptr);
 
   /**
    * Removes callback that was installed by AddMicrotasksCompletedCallback.
    */
   void RemoveMicrotasksCompletedCallback(
       MicrotasksCompletedCallbackWithData callback, void* data = nullptr);
 
   /**
    * Sets a callback for counting the number of times a feature of V8 is used.
    */
   void SetUseCounterCallback(UseCounterCallback callback);
 
   /**
    * Enables the host application to provide a mechanism for recording
    * statistics counters.
    */
   void SetCounterFunction(CounterLookupCallback);
 
   /**
    * Enables the host application to provide a mechanism for recording
    * histograms. The CreateHistogram function returns a
    * histogram which will later be passed to the AddHistogramSample
    * function.
    */
   void SetCreateHistogramFunction(CreateHistogramCallback);
   void SetAddHistogramSampleFunction(AddHistogramSampleCallback);
 
   /**
    * Enables the host application to provide a mechanism for recording
    * event based metrics. In order to use this interface
    *   include/v8-metrics.h
    * needs to be included and the recorder needs to be derived from the
    * Recorder base class defined there.
    * This method can only be called once per isolate and must happen during
    * isolate initialization before background threads are spawned.
    */
   void SetMetricsRecorder(
       const std::shared_ptr<metrics::Recorder>& metrics_recorder);
 
   /**
    * Enables the host application to provide a mechanism for recording a
    * predefined set of data as crash keys to be used in postmortem debugging in
    * case of a crash.
    */
   void SetAddCrashKeyCallback(AddCrashKeyCallback);
 
   /**
    * Optional notification that the system is running low on memory.
    * V8 uses these notifications to attempt to free memory.
    */
   void LowMemoryNotification();
 
   /**
    * Optional notification that a context has been disposed. V8 uses these
    * notifications to guide the GC heuristic and cancel FinalizationRegistry
    * cleanup tasks. Returns the number of context disposals - including this one
    * - since the last time V8 had a chance to clean up.
    *
    * The optional parameter |dependant_context| specifies whether the disposed
    * context was depending on state from other contexts or not.
    */
   V8_DEPRECATE_SOON("Use version that passes ContextDependants.")
   int ContextDisposedNotification(bool dependant_context = true);
 
   /**
    * Optional notification that a context has been disposed. V8 uses these
    * notifications to guide heuristics on e.g. GC or compilers.
    *
    * \param dependants A signal on whether this context possibly had any
    *     dependants.
    */
   void ContextDisposedNotification(ContextDependants dependants);
 
   /**
    * Optional notification that the isolate switched to the foreground.
    * V8 uses these notifications to guide heuristics.
    */
   V8_DEPRECATE_SOON("Use SetPriority(Priority::kUserBlocking) instead")
   void IsolateInForegroundNotification();
 
   /**
    * Optional notification that the isolate switched to the background.
    * V8 uses these notifications to guide heuristics.
    */
   V8_DEPRECATE_SOON("Use SetPriority(Priority::kBestEffort) instead")
   void IsolateInBackgroundNotification();
 
   /**
    * Optional notification that the isolate changed `priority`.
    * V8 uses the priority value to guide heuristics.
    */
   void SetPriority(Priority priority);
 
   /**
    * Optional notification to tell V8 whether the embedder is currently loading
    * resources. If the embedder uses this notification, it should call
    * SetIsLoading(true) when loading starts and SetIsLoading(false) when it
    * ends.
    * It's valid to call SetIsLoading(true) again while loading, which will
    * update the timestamp when V8 considers the load started. Calling
    * SetIsLoading(false) while not loading does nothing.
    * V8 uses these notifications to guide heuristics.
    * This is an unfinished experimental feature. Semantics and implementation
    * may change frequently.
    */
   void SetIsLoading(bool is_loading);
 
   /**
    * Optional notification to tell V8 whether the embedder is currently frozen.
    * V8 uses these notifications to guide heuristics.
    * This is an unfinished experimental feature. Semantics and implementation
    * may change frequently.
    */
   void Freeze(bool is_frozen);
 
   /**
    * Optional notification to tell V8 the current isolate is used for debugging
    * and requires higher heap limit.
    */
   void IncreaseHeapLimitForDebugging();
 
   /**
    * Restores the original heap limit after IncreaseHeapLimitForDebugging().
    */
   void RestoreOriginalHeapLimit();
 
   /**
    * Returns true if the heap limit was increased for debugging and the
    * original heap limit was not restored yet.
    */
   bool IsHeapLimitIncreasedForDebugging();
 
   /**
    * Allows the host application to provide the address of a function that is
    * notified each time code is added, moved or removed.
    *
    * \param options options for the JIT code event handler.
    * \param event_handler the JIT code event handler, which will be invoked
    *     each time code is added, moved or removed.
    * \note \p event_handler won't get notified of existent code.
    * \note since code removal notifications are not currently issued, the
    *     \p event_handler may get notifications of code that overlaps earlier
    *     code notifications. This happens when code areas are reused, and the
    *     earlier overlapping code areas should therefore be discarded.
    * \note the events passed to \p event_handler and the strings they point to
    *     are not guaranteed to live past each call. The \p event_handler must
    *     copy strings and other parameters it needs to keep around.
    * \note the set of events declared in JitCodeEvent::EventType is expected to
    *     grow over time, and the JitCodeEvent structure is expected to accrue
    *     new members. The \p event_handler function must ignore event codes
    *     it does not recognize to maintain future compatibility.
    * \note Use Isolate::CreateParams to get events for code executed during
    *     Isolate setup.
    */
   void SetJitCodeEventHandler(JitCodeEventOptions options,
                               JitCodeEventHandler event_handler);
 
   /**
    * Modifies the stack limit for this Isolate.
    *
    * \param stack_limit An address beyond which the Vm's stack may not grow.
    *
    * \note  If you are using threads then you should hold the V8::Locker lock
    *     while setting the stack limit and you must set a non-default stack
    *     limit separately for each thread.
    */
   void SetStackLimit(uintptr_t stack_limit);
 
   /**
    * Returns a memory range that can potentially contain jitted code. Code for
    * V8's 'builtins' will not be in this range if embedded builtins is enabled.
    *
    * On Win64, embedders are advised to install function table callbacks for
    * these ranges, as default SEH won't be able to unwind through jitted code.
    * The first page of the code range is reserved for the embedder and is
    * committed, writable, and executable, to be used to store unwind data, as
    * documented in
    * https://docs.microsoft.com/en-us/cpp/build/exception-handling-x64.
    *
    * Might be empty on other platforms.
    *
    * https://code.google.com/p/v8/issues/detail?id=3598
    */
   void GetCodeRange(void** start, size_t* length_in_bytes);
 
   /**
    * As GetCodeRange, but for embedded builtins (these live in a distinct
    * memory region from other V8 Code objects).
    */
   void GetEmbeddedCodeRange(const void** start, size_t* length_in_bytes);
 
   /**
    * Returns the JSEntryStubs necessary for use with the Unwinder API.
    */
   JSEntryStubs GetJSEntryStubs();
 
   static constexpr size_t kMinCodePagesBufferSize = 32;
 
   /**
    * Copies the code heap pages currently in use by V8 into |code_pages_out|.
    * |code_pages_out| must have at least kMinCodePagesBufferSize capacity and
    * must be empty.
    *
    * Signal-safe, does not allocate, does not access the V8 heap.
    * No code on the stack can rely on pages that might be missing.
    *
    * Returns the number of pages available to be copied, which might be greater
    * than |capacity|. In this case, only |capacity| pages will be copied into
    * |code_pages_out|. The caller should provide a bigger buffer on the next
    * call in order to get all available code pages, but this is not required.
    */
   size_t CopyCodePages(size_t capacity, MemoryRange* code_pages_out);
 
   /** Set the callback to invoke in case of fatal errors. */
   void SetFatalErrorHandler(FatalErrorCallback that);
 
   /** Set the callback to invoke in case of OOM errors. */
   void SetOOMErrorHandler(OOMErrorCallback that);
 
   /**
    * Add a callback to invoke in case the heap size is close to the heap limit.
    * If multiple callbacks are added, only the most recently added callback is
    * invoked.
    */
   void AddNearHeapLimitCallback(NearHeapLimitCallback callback, void* data);
 
   /**
    * Remove the given callback and restore the heap limit to the
    * given limit. If the given limit is zero, then it is ignored.
    * If the current heap size is greater than the given limit,
    * then the heap limit is restored to the minimal limit that
    * is possible for the current heap size.
    */
   void RemoveNearHeapLimitCallback(NearHeapLimitCallback callback,
                                    size_t heap_limit);
 
   /**
    * If the heap limit was changed by the NearHeapLimitCallback, then the
    * initial heap limit will be restored once the heap size falls below the
    * given threshold percentage of the initial heap limit.
    * The threshold percentage is a number in (0.0, 1.0) range.
    */
   void AutomaticallyRestoreInitialHeapLimit(double threshold_percent = 0.5);
 
   /**
    * Set the callback to invoke to check if code generation from
    * strings should be allowed.
    */
   void SetModifyCodeGenerationFromStringsCallback(
       ModifyCodeGenerationFromStringsCallback2 callback);
 
   /**
    * Set the callback to invoke to check if wasm code generation should
    * be allowed.
    */
   void SetAllowWasmCodeGenerationCallback(
       AllowWasmCodeGenerationCallback callback);
 
   /**
    * Embedder over{ride|load} injection points for wasm APIs. The expectation
    * is that the embedder sets them at most once.
    */
   void SetWasmModuleCallback(ExtensionCallback callback);
   void SetWasmInstanceCallback(ExtensionCallback callback);
 
   void SetWasmStreamingCallback(WasmStreamingCallback callback);
 
   void SetWasmAsyncResolvePromiseCallback(
       WasmAsyncResolvePromiseCallback callback);
 
   void SetWasmLoadSourceMapCallback(WasmLoadSourceMapCallback callback);
 
   void SetWasmImportedStringsEnabledCallback(
       WasmImportedStringsEnabledCallback callback);
 
   void SetSharedArrayBufferConstructorEnabledCallback(
       SharedArrayBufferConstructorEnabledCallback callback);
 
   void SetWasmJSPIEnabledCallback(WasmJSPIEnabledCallback callback);
 
   /**
    * Register callback to control whether compile hints magic comments are
    * enabled.
    */
   V8_DEPRECATED(
       "Will be removed, use ScriptCompiler::CompileOptions for enabling the "
       "compile hints magic comments")
   void SetJavaScriptCompileHintsMagicEnabledCallback(
       JavaScriptCompileHintsMagicEnabledCallback callback);
 
   /**
    * This function can be called by the embedder to signal V8 that the dynamic
    * enabling of features has finished. V8 can now set up dynamically added
    * features.
    */
   void InstallConditionalFeatures(Local<Context> context);
 
   /**
    * Check if V8 is dead and therefore unusable.  This is the case after
    * fatal errors such as out-of-memory situations.
    */
   bool IsDead();
 
   /**
    * Adds a message listener (errors only).
    *
    * The same message listener can be added more than once and in that
    * case it will be called more than once for each message.
    *
    * If data is specified, it will be passed to the callback when it is called.
    * Otherwise, the exception object will be passed to the callback instead.
    */
   bool AddMessageListener(MessageCallback that,
                           Local<Value> data = Local<Value>());
 
   /**
    * Adds a message listener.
    *
    * The same message listener can be added more than once and in that
    * case it will be called more than once for each message.
    *
    * If data is specified, it will be passed to the callback when it is called.
    * Otherwise, the exception object will be passed to the callback instead.
    *
    * A listener can listen for particular error levels by providing a mask.
    */
   bool AddMessageListenerWithErrorLevel(MessageCallback that,
                                         int message_levels,
                                         Local<Value> data = Local<Value>());
 
   /**
    * Remove all message listeners from the specified callback function.
    */
   void RemoveMessageListeners(MessageCallback that);
 
   /** Callback function for reporting failed access checks.*/
   void SetFailedAccessCheckCallbackFunction(FailedAccessCheckCallback);
 
   /**
    * Tells V8 to capture current stack trace when uncaught exception occurs
    * and report it to the message listeners. The option is off by default.
    */
   void SetCaptureStackTraceForUncaughtExceptions(
       bool capture, int frame_limit = 10,
       StackTrace::StackTraceOptions options = StackTrace::kOverview);
 
   /**
    * Check if this isolate is in use.
    * True if at least one thread Enter'ed this isolate.
    */
   bool IsInUse();
 
   /**
    * Set whether calling Atomics.wait (a function that may block) is allowed in
    * this isolate. This can also be configured via
    * CreateParams::allow_atomics_wait.
    */
   void SetAllowAtomicsWait(bool allow);
 
   /**
    * Time zone redetection indicator for
    * DateTimeConfigurationChangeNotification.
    *
    * kSkip indicates V8 that the notification should not trigger redetecting
    * host time zone. kRedetect indicates V8 that host time zone should be
    * redetected, and used to set the default time zone.
    *
    * The host time zone detection may require file system access or similar
    * operations unlikely to be available inside a sandbox. If v8 is run inside a
    * sandbox, the host time zone has to be detected outside the sandbox before
    * calling DateTimeConfigurationChangeNotification function.
    */
   enum class TimeZoneDetection { kSkip, kRedetect };
 
   /**
    * Notification that the embedder has changed the time zone, daylight savings
    * time or other date / time configuration parameters. V8 keeps a cache of
    * various values used for date / time computation. This notification will
    * reset those cached values for the current context so that date / time
    * configuration changes would be reflected.
    *
    * This API should not be called more than needed as it will negatively impact
    * the performance of date operations.
    */
   void DateTimeConfigurationChangeNotification(
       TimeZoneDetection time_zone_detection = TimeZoneDetection::kSkip);
 
   /**
    * Notification that the embedder has changed the locale. V8 keeps a cache of
    * various values used for locale computation. This notification will reset
    * those cached values for the current context so that locale configuration
    * changes would be reflected.
    *
    * This API should not be called more than needed as it will negatively impact
    * the performance of locale operations.
    */
   void LocaleConfigurationChangeNotification();
 
   /**
    * Returns the default locale in a string if Intl support is enabled.
    * Otherwise returns an empty string.
    */
   std::string GetDefaultLocale();
 
   /**
    * Returns the hash seed for that isolate, for testing purposes.
    */
   uint64_t GetHashSeed();
 
   Isolate() = delete;
   ~Isolate() = delete;
   Isolate(const Isolate&) = delete;
   Isolate& operator=(const Isolate&) = delete;
   // Deleting operator new and delete here is allowed as ctor and dtor is also
   // deleted.
   void* operator new(size_t size) = delete;
   void* operator new[](size_t size) = delete;
   void operator delete(void*, size_t) = delete;
   void operator delete[](void*, size_t) = delete;
 
  private:
   template <class K, class V, class Traits>
   friend class PersistentValueMapBase;
   friend class ExternalMemoryAccounter;
 
   internal::ValueHelper::InternalRepresentationType GetDataFromSnapshotOnce(
       size_t index);
   int64_t AdjustAmountOfExternalAllocatedMemoryImpl(int64_t change_in_bytes);
   void HandleExternalMemoryInterrupt();
 };
 
 void Isolate::SetData(uint32_t slot, void* data) {
   using I = internal::Internals;
   I::SetEmbedderData(this, slot, data);
 }
 
 void* Isolate::GetData(uint32_t slot) {
   using I = internal::Internals;
   return I::GetEmbedderData(this, slot);
 }
 
 uint32_t Isolate::GetNumberOfDataSlots() {
   using I = internal::Internals;
   return I::kNumIsolateDataSlots;
 }
 
 template <class T>
 MaybeLocal<T> Isolate::GetDataFromSnapshotOnce(size_t index) {
   if (auto repr = GetDataFromSnapshotOnce(index);
       repr != internal::ValueHelper::kEmpty) {
     internal::PerformCastCheck(internal::ValueHelper::ReprAsValue<T>(repr));
     return Local<T>::FromRepr(repr);
   }
   return {};
 }
 
 }  // namespace v8
 
 #endif  // INCLUDE_V8_ISOLATE_H_

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