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/* -*- 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 */
/* JS execution context. */
#ifndef vm_JSContext_h
#define vm_JSContext_h
#include "mozilla/Maybe.h"
#include "mozilla/MemoryReporting.h"
#include "jstypes.h" // JS_PUBLIC_API
#include "builtin/AtomicsObject.h"
#include "ds/TraceableFifo.h"
#include "frontend/NameCollections.h"
#include "gc/GCEnum.h"
#include "gc/Memory.h"
#include "irregexp/RegExpTypes.h"
#include "jit/PcScriptCache.h"
#include "js/ContextOptions.h" // JS::ContextOptions
#include "js/Exception.h"
#include "js/GCVector.h"
#include "js/Interrupt.h"
#include "js/Promise.h"
#include "js/Result.h"
#include "js/Stack.h" // JS::NativeStackBase, JS::NativeStackLimit
#include "js/Utility.h"
#include "js/Vector.h"
#include "threading/ProtectedData.h"
#include "util/StructuredSpewer.h"
#include "vm/Activation.h" // js::Activation
#include "vm/MallocProvider.h"
#include "vm/Runtime.h"
#include "wasm/WasmContext.h"
struct JS_PUBLIC_API JSContext;
struct DtoaState;
namespace js {
class AutoAllocInAtomsZone;
class AutoMaybeLeaveAtomsZone;
class AutoRealm;
struct PortableBaselineStack;
namespace jit {
class ICScript;
class JitActivation;
class JitContext;
class DebugModeOSRVolatileJitFrameIter;
} // namespace jit
/* Detects cycles when traversing an object graph. */
class MOZ_RAII AutoCycleDetector {
using Vector = GCVector<JSObject*, 8>;
AutoCycleDetector(JSContext* cx, HandleObject objArg)
: cx(cx), obj(cx, objArg), cyclic(true) {}
bool init();
bool foundCycle() { return cyclic; }
JSContext* cx;
RootedObject obj;
bool cyclic;
struct AutoResolving;
class InternalJobQueue : public JS::JobQueue {
explicit InternalJobQueue(JSContext* cx)
: queue(cx, SystemAllocPolicy()), draining_(false), interrupted_(false) {}
~InternalJobQueue() = default;
// JS::JobQueue methods.
JSObject* getIncumbentGlobal(JSContext* cx) override;
bool enqueuePromiseJob(JSContext* cx, JS::HandleObject promise,
JS::HandleObject job, JS::HandleObject allocationSite,
JS::HandleObject incumbentGlobal) override;
void runJobs(JSContext* cx) override;
bool empty() const override;
// If we are currently in a call to runJobs(), make that call stop processing
// jobs once the current one finishes, and return. If we are not currently in
// a call to runJobs, make all future calls return immediately.
void interrupt() { interrupted_ = true; }
// Return the front element of the queue, or nullptr if the queue is empty.
// This is only used by shell testing functions.
JSObject* maybeFront() const;
#ifdef DEBUG
JSObject* copyJobs(JSContext* cx);
using Queue = js::TraceableFifo<JSObject*, 0, SystemAllocPolicy>;
JS::PersistentRooted<Queue> queue;
// True if we are in the midst of draining jobs from this queue. We use this
// to avoid re-entry (nested calls simply return immediately).
bool draining_;
// True if we've been asked to interrupt draining jobs. Set by interrupt().
bool interrupted_;
class SavedQueue;
js::UniquePtr<JobQueue::SavedJobQueue> saveJobQueue(JSContext*) override;
class AutoLockScriptData;
/* Thread Local Storage slot for storing the context for a thread. */
extern MOZ_THREAD_LOCAL(JSContext*) TlsContext;
#ifdef DEBUG
JSContext* MaybeGetJSContext();
enum class InterruptReason : uint32_t {
MinorGC = 1 << 0,
MajorGC = 1 << 1,
AttachIonCompilations = 1 << 2,
CallbackUrgent = 1 << 3,
CallbackCanWait = 1 << 4,
enum class ShouldCaptureStack { Maybe, Always };
} /* namespace js */
* A JSContext encapsulates the thread local state used when using the JS
* runtime.
struct JS_PUBLIC_API JSContext : public JS::RootingContext,
public js::MallocProvider<JSContext> {
JSContext(JSRuntime* runtime, const JS::ContextOptions& options);
bool init();
static JSContext* from(JS::RootingContext* rcx) {
return static_cast<JSContext*>(rcx);
js::UnprotectedData<JSRuntime*> runtime_;
#ifdef DEBUG
js::WriteOnceData<bool> initialized_;
js::ContextData<JS::ContextOptions> options_;
// Are we currently timing execution? This flag ensures that we do not
// double-count execution time in reentrant situations.
js::ContextData<bool> measuringExecutionTime_;
// This variable is used by the HelperThread scheduling to update the priority
// of task based on whether JavaScript is being executed on the main thread.
mozilla::Atomic<bool, mozilla::ReleaseAcquire> isExecuting_;
// This is used by helper threads to change the runtime their context is
// currently operating on.
void setRuntime(JSRuntime* rt);
bool isMeasuringExecutionTime() const { return measuringExecutionTime_; }
void setIsMeasuringExecutionTime(bool value) {
measuringExecutionTime_ = value;
// While JSContexts are meant to be used on a single thread, this reference is
// meant to be shared to helper thread tasks. This is used by helper threads
// to change the priority of tasks based on whether JavaScript is executed on
// the main thread.
const mozilla::Atomic<bool, mozilla::ReleaseAcquire>& isExecutingRef() const {
return isExecuting_;
void setIsExecuting(bool value) { isExecuting_ = value; }
#ifdef DEBUG
bool isInitialized() const { return initialized_; }
template <typename T>
bool isInsideCurrentZone(T thing) const {
return thing->zoneFromAnyThread() == zone_;
template <typename T>
inline bool isInsideCurrentCompartment(T thing) const {
return thing->compartment() == compartment();
void onOutOfMemory();
void* onOutOfMemory(js::AllocFunction allocFunc, arena_id_t arena,
size_t nbytes, void* reallocPtr = nullptr) {
return runtime_->onOutOfMemory(allocFunc, arena, nbytes, reallocPtr, this);
void onOverRecursed();
// Allocate a GC thing.
template <typename T, js::AllowGC allowGC = js::CanGC, typename... Args>
T* newCell(Args&&... args);
/* Clear the pending exception (if any) due to OOM. */
void recoverFromOutOfMemory();
void reportAllocationOverflow();
// Accessors for immutable runtime data.
JSAtomState& names() { return *runtime_->commonNames; }
js::StaticStrings& staticStrings() { return *runtime_->staticStrings; }
bool permanentAtomsPopulated() { return runtime_->permanentAtomsPopulated(); }
const js::FrozenAtomSet& permanentAtoms() {
return *runtime_->permanentAtoms();
js::WellKnownSymbols& wellKnownSymbols() {
return *runtime_->wellKnownSymbols;
js::PropertyName* emptyString() { return runtime_->emptyString; }
JS::GCContext* gcContext() { return runtime_->gcContext(); }
JS::StackKind stackKindForCurrentPrincipal();
JS::NativeStackLimit stackLimitForCurrentPrincipal();
JS::NativeStackLimit stackLimit(JS::StackKind kind) {
return nativeStackLimit[kind];
JS::NativeStackLimit stackLimitForJitCode(JS::StackKind kind);
size_t gcSystemPageSize() { return js::gc::SystemPageSize(); }
* "Entering" a realm changes cx->realm (which changes cx->global). Note
* that this does not push an Activation so it's possible for the caller's
* realm to be != cx->realm(). This is not a problem since, in general, most
* places in the VM cannot know that they were called from script (e.g.,
* they may have been called through the JSAPI via JS_CallFunction) and thus
* cannot expect there is a scripted caller.
* Realms should be entered/left in a LIFO fasion. To enter a realm, code
* should prefer using AutoRealm over JS::EnterRealm/JS::LeaveRealm.
* Also note that the JIT can enter (same-compartment) realms without going
* through these methods - it will update cx->realm_ directly.
inline void setRealm(JS::Realm* realm);
inline void enterRealm(JS::Realm* realm);
inline void enterAtomsZone();
inline void leaveAtomsZone(JS::Realm* oldRealm);
inline void setZone(js::Zone* zone);
friend class js::AutoAllocInAtomsZone;
friend class js::AutoMaybeLeaveAtomsZone;
friend class js::AutoRealm;
inline void enterRealmOf(JSObject* target);
inline void enterRealmOf(JSScript* target);
inline void enterRealmOf(js::Shape* target);
inline void enterNullRealm();
inline void setRealmForJitExceptionHandler(JS::Realm* realm);
inline void leaveRealm(JS::Realm* oldRealm);
// Threads may freely access any data in their realm, compartment and zone.
JS::Compartment* compartment() const {
return realm_ ? JS::GetCompartmentForRealm(realm_) : nullptr;
JS::Realm* realm() const { return realm_; }
#ifdef DEBUG
bool inAtomsZone() const;
JS::Zone* zone() const {
MOZ_ASSERT_IF(!realm() && zone_, inAtomsZone());
MOZ_ASSERT_IF(realm(), js::GetRealmZone(realm()) == zone_);
return zone_;
// For JIT use.
static size_t offsetOfZone() { return offsetof(JSContext, zone_); }
// Current global. This is only safe to use within the scope of the
// AutoRealm from which it's called.
inline js::Handle<js::GlobalObject*> global() const;
js::AtomsTable& atoms() { return runtime_->atoms(); }
js::SymbolRegistry& symbolRegistry() { return runtime_->symbolRegistry(); }
// Methods to access other runtime data that checks locking internally.
js::gc::AtomMarkingRuntime& atomMarking() { return runtime_->gc.atomMarking; }
void markAtom(JSAtom* atom) { atomMarking().markAtom(this, atom); }
void markAtom(JS::Symbol* symbol) { atomMarking().markAtom(this, symbol); }
void markId(jsid id) { atomMarking().markId(this, id); }
void markAtomValue(const js::Value& value) {
atomMarking().markAtomValue(this, value);
// Interface for recording telemetry metrics.
js::Metrics metrics() { return js::Metrics(runtime_); }
JSRuntime* runtime() { return runtime_; }
const JSRuntime* runtime() const { return runtime_; }
static size_t offsetOfRealm() { return offsetof(JSContext, realm_); }
friend class JS::AutoSaveExceptionState;
friend class js::jit::DebugModeOSRVolatileJitFrameIter;
friend void js::ReportOutOfMemory(JSContext*);
friend void js::ReportOverRecursed(JSContext*);
friend void js::ReportOversizedAllocation(JSContext*, const unsigned);
* Intentionally awkward signpost method that is stationed on the
* boundary between Result-using and non-Result-using code.
template <typename V, typename E>
bool resultToBool(const JS::Result<V, E>& result) {
return result.isOk();
template <typename V, typename E>
V* resultToPtr(JS::Result<V*, E>& result) {
return result.isOk() ? result.unwrap() : nullptr;
mozilla::GenericErrorResult<JS::OOM> alreadyReportedOOM();
mozilla::GenericErrorResult<JS::Error> alreadyReportedError();
* Points to the most recent JitActivation pushed on the thread.
* See JitActivation constructor in vm/Stack.cpp
js::ContextData<js::jit::JitActivation*> jitActivation;
// Shim for V8 interfaces used by irregexp code
js::ContextData<js::irregexp::Isolate*> isolate;
* Points to the most recent activation running on the thread.
* See Activation comment in vm/Stack.h.
js::ContextData<js::Activation*> activation_;
* Points to the most recent profiling activation running on the
* thread.
js::Activation* volatile profilingActivation_;
js::Activation* activation() const { return activation_; }
static size_t offsetOfActivation() {
return offsetof(JSContext, activation_);
js::Activation* profilingActivation() const { return profilingActivation_; }
static size_t offsetOfProfilingActivation() {
return offsetof(JSContext, profilingActivation_);
static size_t offsetOfJitActivation() {
return offsetof(JSContext, jitActivation);
#ifdef DEBUG
static size_t offsetOfInUnsafeCallWithABI() {
return offsetof(JSContext, inUnsafeCallWithABI);
static size_t offsetOfInlinedICScript() {
return offsetof(JSContext, inlinedICScript_);
js::InterpreterStack& interpreterStack() {
return runtime()->interpreterStack();
js::PortableBaselineStack& portableBaselineStack() {
return runtime()->portableBaselineStack();
// Base address of the native stack for the current thread.
mozilla::Maybe<JS::NativeStackBase> nativeStackBase_;
JS::NativeStackBase nativeStackBase() const { return *nativeStackBase_; }
/* If non-null, report JavaScript entry points to this monitor. */
js::ContextData<JS::dbg::AutoEntryMonitor*> entryMonitor;
* Stack of debuggers that currently disallow debuggee execution.
* When we check for NX we are inside the debuggee compartment, and thus a
* stack of Debuggers that have prevented execution need to be tracked to
* enter the correct Debugger compartment to report the error.
js::ContextData<js::EnterDebuggeeNoExecute*> noExecuteDebuggerTop;
#ifdef DEBUG
js::ContextData<uint32_t> inUnsafeCallWithABI;
js::ContextData<bool> hasAutoUnsafeCallWithABI;
js::ContextData<js::jit::Simulator*> simulator_;
js::jit::Simulator* simulator() const;
JS::NativeStackLimit* addressOfSimulatorStackLimit();
// State used by util/DoubleToString.cpp.
js::ContextData<DtoaState*> dtoaState;
* When this flag is non-zero, any attempt to GC will be skipped. See the
* AutoSuppressGC class for for details.
js::ContextData<int32_t> suppressGC;
uint32_t executionHash;
uint32_t executionHashInputs;
#ifdef DEBUG
js::ContextData<size_t> noNurseryAllocationCheck;
* If this is 0, all cross-compartment proxies must be registered in the
* wrapper map. This checking must be disabled temporarily while creating
* new wrappers. When non-zero, this records the recursion depth of wrapper
* creation.
js::ContextData<uintptr_t> disableStrictProxyCheckingCount;
bool isNurseryAllocAllowed() { return noNurseryAllocationCheck == 0; }
void disallowNurseryAlloc() { ++noNurseryAllocationCheck; }
void allowNurseryAlloc() {
bool isStrictProxyCheckingEnabled() {
return disableStrictProxyCheckingCount == 0;
void disableStrictProxyChecking() { ++disableStrictProxyCheckingCount; }
void enableStrictProxyChecking() {
MOZ_ASSERT(disableStrictProxyCheckingCount > 0);
#if defined(DEBUG) || defined(JS_OOM_BREAKPOINT)
// We are currently running a simulated OOM test.
js::ContextData<bool> runningOOMTest;
* Some regions of code are hard for the static rooting hazard analysis to
* understand. In those cases, we trade the static analysis for a dynamic
* analysis. When this is non-zero, we should assert if we trigger, or
* might trigger, a GC.
js::ContextData<int> inUnsafeRegion;
// Count of AutoDisableGenerationalGC instances on the thread's stack.
js::ContextData<unsigned> generationalDisabled;
// Some code cannot tolerate compacting GC so it can be disabled temporarily
// with AutoDisableCompactingGC which uses this counter.
js::ContextData<unsigned> compactingDisabledCount;
// Match limit result for the most recent call to RegExpSearcher.
js::ContextData<uint32_t> regExpSearcherLastLimit;
static constexpr size_t offsetOfRegExpSearcherLastLimit() {
return offsetof(JSContext, regExpSearcherLastLimit);
// Pools used for recycling name maps and vectors when parsing and
// emitting bytecode. Purged on GC when there are no active script
// compilations.
js::ContextData<js::frontend::NameCollectionPool> frontendCollectionPool_;
js::frontend::NameCollectionPool& frontendCollectionPool() {
return frontendCollectionPool_.ref();
void verifyIsSafeToGC() {
"[AutoAssertNoGC] possible GC in GC-unsafe region");
bool isInUnsafeRegion() const { return bool(inUnsafeRegion); }
// For JIT use.
MOZ_NEVER_INLINE void resetInUnsafeRegion() {
MOZ_ASSERT(inUnsafeRegion >= 0);
inUnsafeRegion = 0;
static constexpr size_t offsetOfInUnsafeRegion() {
return offsetof(JSContext, inUnsafeRegion);
/* Whether sampling should be enabled or not. */
mozilla::Atomic<bool, mozilla::SequentiallyConsistent>
bool isProfilerSamplingEnabled() const { return !suppressProfilerSampling; }
void disableProfilerSampling() { suppressProfilerSampling = true; }
void enableProfilerSampling() { suppressProfilerSampling = false; }
js::wasm::Context wasm_;
js::wasm::Context& wasm() { return wasm_; }
/* Temporary arena pool used while compiling and decompiling. */
static const size_t TEMP_LIFO_ALLOC_PRIMARY_CHUNK_SIZE = 4 * 1024;
js::ContextData<js::LifoAlloc> tempLifoAlloc_;
js::LifoAlloc& tempLifoAlloc() { return tempLifoAlloc_.ref(); }
const js::LifoAlloc& tempLifoAlloc() const { return tempLifoAlloc_.ref(); }
js::ContextData<uint32_t> debuggerMutations;
// Cache for jit::GetPcScript().
js::ContextData<js::UniquePtr<js::jit::PcScriptCache>> ionPcScriptCache;
// Indicates if an exception is pending and the reason for it.
js::ContextData<JS::ExceptionStatus> status;
unwrappedException_; /* most-recently-thrown exception */
unwrappedExceptionStack_; /* stack when the exception was thrown */
JS::Value& unwrappedException() {
if (!unwrappedException_.ref().initialized()) {
return unwrappedException_.ref().get();
js::SavedFrame*& unwrappedExceptionStack() {
if (!unwrappedExceptionStack_.ref().initialized()) {
return unwrappedExceptionStack_.ref().get();
#ifdef DEBUG
// True if this context has ever thrown an exception because of an exceeded
// limit: stack space (ReportOverRecursed), memory (ReportOutOfMemory), or
// some other self-imposed limit (eg ReportOversizedAllocation). Used when
// detecting bailout loops in WarpOracle: bailout loops involving resource
// exhaustion are generally not interesting.
js::ContextData<bool> hadResourceExhaustion_;
bool hadResourceExhaustion() const {
return hadResourceExhaustion_ || js::oom::simulator.isThreadSimulatingAny();
void reportResourceExhaustion() {
#ifdef DEBUG
hadResourceExhaustion_ = true;
js::ContextData<int32_t> reportGranularity; /* see vm/Probes.h */
js::ContextData<js::AutoResolving*> resolvingList;
#ifdef DEBUG
js::ContextData<js::AutoEnterPolicy*> enteredPolicy;
/* True if generating an error, to prevent runaway recursion. */
js::ContextData<bool> generatingError;
/* State for object and array toSource conversion. */
js::ContextData<js::AutoCycleDetector::Vector> cycleDetectorVector_;
js::AutoCycleDetector::Vector& cycleDetectorVector() {
return cycleDetectorVector_.ref();
const js::AutoCycleDetector::Vector& cycleDetectorVector() const {
return cycleDetectorVector_.ref();
/* Client opaque pointer. */
js::UnprotectedData<void*> data;
void initJitStackLimit();
void resetJitStackLimit();
JS::ContextOptions& options() { return options_.ref(); }
bool runtimeMatches(JSRuntime* rt) const { return runtime_ == rt; }
* Youngest frame of a saved stack that will be picked up as an async stack
* by any new Activation, and is nullptr when no async stack should be used.
* The JS::AutoSetAsyncStackForNewCalls class can be used to set this.
* New activations will reset this to nullptr on construction after getting
* the current value, and will restore the previous value on destruction.
js::SavedFrame*& asyncStackForNewActivations() {
if (!asyncStackForNewActivations_.ref().initialized()) {
return asyncStackForNewActivations_.ref().get();
* Value of asyncCause to be attached to asyncStackForNewActivations.
js::ContextData<const char*> asyncCauseForNewActivations;
* True if the async call was explicitly requested, e.g. via
* callFunctionWithAsyncStack.
js::ContextData<bool> asyncCallIsExplicit;
bool currentlyRunningInInterpreter() const {
return activation()->isInterpreter();
bool currentlyRunningInJit() const { return activation()->isJit(); }
js::InterpreterFrame* interpreterFrame() const {
return activation()->asInterpreter()->current();
js::InterpreterRegs& interpreterRegs() const {
return activation()->asInterpreter()->regs();
* Get the topmost script and optional pc on the stack. By default, this
* function only returns a JSScript in the current realm, returning nullptr
* if the current script is in a different realm. This behavior can be
* overridden by passing AllowCrossRealm::Allow.
enum class AllowCrossRealm { DontAllow = false, Allow = true };
inline JSScript* currentScript(
jsbytecode** pc = nullptr,
AllowCrossRealm allowCrossRealm = AllowCrossRealm::DontAllow) const;
inline void minorGC(JS::GCReason reason);
bool isExceptionPending() const {
return JS::IsCatchableExceptionStatus(status);
* Return the pending exception and wrap it into the current compartment.
[[nodiscard]] bool getPendingException(JS::MutableHandleValue rval);
* Return the pending exception stack and wrap it into the current
* compartment. Return |JS::NullValue| when the pending exception has no stack
* attached.
[[nodiscard]] bool getPendingExceptionStack(JS::MutableHandleValue rval);
* Return the pending exception stack, but does not wrap it into the current
* compartment. Return |nullptr| when the pending exception has no stack
* attached.
js::SavedFrame* getPendingExceptionStack();
bool isThrowingDebuggeeWouldRun();
bool isClosingGenerator();
void setPendingException(JS::HandleValue v,
JS::Handle<js::SavedFrame*> stack);
void setPendingException(JS::HandleValue v,
js::ShouldCaptureStack captureStack);
void clearPendingException() {
status = JS::ExceptionStatus::None;
unwrappedExceptionStack() = nullptr;
bool isThrowingOutOfMemory() const {
return status == JS::ExceptionStatus::OutOfMemory;
bool isThrowingOverRecursed() const {
return status == JS::ExceptionStatus::OverRecursed;
bool isPropagatingForcedReturn() const {
return status == JS::ExceptionStatus::ForcedReturn;
void setPropagatingForcedReturn() {
MOZ_ASSERT(status == JS::ExceptionStatus::None);
status = JS::ExceptionStatus::ForcedReturn;
void clearPropagatingForcedReturn() {
MOZ_ASSERT(status == JS::ExceptionStatus::ForcedReturn);
status = JS::ExceptionStatus::None;
* See JS_SetTrustedPrincipals in jsapi.h.
* Note: !cx->realm() is treated as trusted.
inline bool runningWithTrustedPrincipals();
// Checks if the page's Content-Security-Policy (CSP) allows
// runtime code generation "unsafe-eval", or "wasm-unsafe-eval" for Wasm.
bool isRuntimeCodeGenEnabled(JS::RuntimeCode kind, js::HandleString code);
size_t sizeOfExcludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
size_t sizeOfIncludingThis(mozilla::MallocSizeOf mallocSizeOf) const;
void trace(JSTracer* trc);
inline js::RuntimeCaches& caches();
using InterruptCallbackVector =
js::Vector<JSInterruptCallback, 2, js::SystemAllocPolicy>;
js::ContextData<InterruptCallbackVector> interruptCallbacks_;
InterruptCallbackVector& interruptCallbacks() {
return interruptCallbacks_.ref();
js::ContextData<bool> interruptCallbackDisabled;
// Bitfield storing InterruptReason values.
mozilla::Atomic<uint32_t, mozilla::Relaxed> interruptBits_;
// Any thread can call requestInterrupt() to request that this thread
// stop running. To stop this thread, requestInterrupt sets two fields:
// interruptBits_ (a bitset of InterruptReasons) and jitStackLimit (set to
// JS::NativeStackLimitMin). The JS engine must continually poll one of these
// fields and call handleInterrupt if either field has the interrupt value.
// The point of setting jitStackLimit to JS::NativeStackLimitMin is that JIT
// code already needs to guard on jitStackLimit in every function prologue to
// avoid stack overflow, so we avoid a second branch on interruptBits_ by
// setting jitStackLimit to a value that is guaranteed to fail the guard.)
// Note that the writes to interruptBits_ and jitStackLimit use a Relaxed
// Atomic so, while the writes are guaranteed to eventually be visible to
// this thread, it can happen in any order. handleInterrupt calls the
// interrupt callback if either is set, so it really doesn't matter as long
// as the JS engine is continually polling at least one field. In corner
// cases, this relaxed ordering could lead to an interrupt handler being
// called twice in succession after a single requestInterrupt call, but
// that's fine.
void requestInterrupt(js::InterruptReason reason);
bool handleInterrupt();
MOZ_ALWAYS_INLINE bool hasAnyPendingInterrupt() const {
static_assert(sizeof(interruptBits_) == sizeof(uint32_t),
"Assumed by JIT callers");
return interruptBits_ != 0;
bool hasPendingInterrupt(js::InterruptReason reason) const {
return interruptBits_ & uint32_t(reason);
void clearPendingInterrupt(js::InterruptReason reason);
// For JIT use. Points to the inlined ICScript for a baseline script
// being invoked as part of a trial inlining. Contains nullptr at
// all times except for the brief moment between being set in the
// caller and read in the callee's prologue.
js::ContextData<js::jit::ICScript*> inlinedICScript_;
void* addressOfInterruptBits() { return &interruptBits_; }
void* addressOfJitStackLimit() { return &jitStackLimit; }
void* addressOfJitStackLimitNoInterrupt() {
return &jitStackLimitNoInterrupt;
void* addressOfZone() { return &zone_; }
const void* addressOfRealm() const { return &realm_; }
void* addressOfInlinedICScript() { return &inlinedICScript_; }
// Futex state, used by Atomics.wait() and Atomics.wake() on the Atomics
// object.
js::FutexThread fx;
mozilla::Atomic<JS::NativeStackLimit, mozilla::Relaxed> jitStackLimit;
// Like jitStackLimit, but not reset to trigger interrupts.
js::ContextData<JS::NativeStackLimit> jitStackLimitNoInterrupt;
// Queue of pending jobs as described in ES2016 section 8.4.
// This is a non-owning pointer to either:
// - a JobQueue implementation the embedding provided by calling
// JS::SetJobQueue, owned by the embedding, or
// - our internal JobQueue implementation, established by calling
// js::UseInternalJobQueues, owned by JSContext::internalJobQueue below.
js::ContextData<JS::JobQueue*> jobQueue;
// If the embedding has called js::UseInternalJobQueues, this is the owning
// pointer to our internal JobQueue implementation, which JSContext::jobQueue
// borrows.
js::ContextData<js::UniquePtr<js::InternalJobQueue>> internalJobQueue;
// True if jobQueue is empty, or we are running the last job in the queue.
// Such conditions permit optimizations around `await` expressions.
js::ContextData<bool> canSkipEnqueuingJobs;
js::ContextData<void*> promiseRejectionTrackerCallbackData;
JSObject* getIncumbentGlobal(JSContext* cx);
bool enqueuePromiseJob(JSContext* cx, js::HandleFunction job,
js::HandleObject promise,
js::HandleObject incumbentGlobal);
void addUnhandledRejectedPromise(JSContext* cx, js::HandleObject promise);
void removeUnhandledRejectedPromise(JSContext* cx, js::HandleObject promise);
template <class... Args>
inline void checkImpl(const Args&... args);
bool contextChecksEnabled() const {
// Don't perform these checks when called from a finalizer. The checking
// depends on other objects not having been swept yet.
return !RuntimeHeapIsCollecting(runtime()->heapState());
// Assert the arguments are in this context's realm (for scripts),
// compartment (for objects) or zone (for strings, symbols).
template <class... Args>
inline void check(const Args&... args);
template <class... Args>
inline void releaseCheck(const Args&... args);
template <class... Args>
MOZ_ALWAYS_INLINE void debugOnlyCheck(const Args&... args);
// Spewer for this thread
js::UnprotectedData<js::StructuredSpewer> structuredSpewer_;
js::StructuredSpewer& spewer() { return structuredSpewer_.ref(); }
// Debugger having set `exclusiveDebuggerOnEval` property to true
// want their evaluations and calls to be ignore by all other Debuggers
// except themself. This flag indicates whether we are in such debugger
// evaluation, and which debugger initiated the evaluation. This debugger
// has other references on the stack and does not need to be traced.
js::ContextData<js::Debugger*> insideExclusiveDebuggerOnEval;
}; /* struct JSContext */
inline JSContext* JSRuntime::mainContextFromOwnThread() {
MOZ_ASSERT(mainContextFromAnyThread() == js::TlsContext.get());
return mainContextFromAnyThread();
namespace js {
struct MOZ_RAII AutoResolving {
enum Kind { LOOKUP, WATCH };
AutoResolving(JSContext* cx, HandleObject obj, HandleId id,
Kind kind = LOOKUP)
: context(cx), object(obj), id(id), kind(kind), link(cx->resolvingList) {
cx->resolvingList = this;
~AutoResolving() {
MOZ_ASSERT(context->resolvingList == this);
context->resolvingList = link;
bool alreadyStarted() const { return link && alreadyStartedSlow(); }
bool alreadyStartedSlow() const;
JSContext* const context;
HandleObject object;
HandleId id;
Kind const kind;
AutoResolving* const link;
* Create and destroy functions for JSContext, which is manually allocated
* and exclusively owned.
extern JSContext* NewContext(uint32_t maxBytes, JSRuntime* parentRuntime);
extern void DestroyContext(JSContext* cx);
/* |callee| requires a usage string provided by JS_DefineFunctionsWithHelp. */
extern void ReportUsageErrorASCII(JSContext* cx, HandleObject callee,
const char* msg);
extern void ReportIsNotDefined(JSContext* cx, Handle<PropertyName*> name);
extern void ReportIsNotDefined(JSContext* cx, HandleId id);
* Report an attempt to access the property of a null or undefined value (v).
extern void ReportIsNullOrUndefinedForPropertyAccess(JSContext* cx,
HandleValue v, int vIndex);
extern void ReportIsNullOrUndefinedForPropertyAccess(JSContext* cx,
HandleValue v, int vIndex,
HandleId key);
* Report error using js::DecompileValueGenerator(cx, spindex, v, fallback) as
* the first argument for the error message.
extern bool ReportValueError(JSContext* cx, const unsigned errorNumber,
int spindex, HandleValue v, HandleString fallback,
const char* arg1 = nullptr,
const char* arg2 = nullptr);
JSObject* CreateErrorNotesArray(JSContext* cx, JSErrorReport* report);
* Encapsulates an external array of values and adds a trace method, for use in
* Rooted.
class MOZ_STACK_CLASS ExternalValueArray {
ExternalValueArray(size_t len, Value* vec) : array_(vec), length_(len) {}
Value* begin() { return array_; }
size_t length() { return length_; }
void trace(JSTracer* trc);
Value* array_;
size_t length_;
/* RootedExternalValueArray roots an external array of Values. */
class MOZ_RAII RootedExternalValueArray
: public JS::Rooted<ExternalValueArray> {
RootedExternalValueArray(JSContext* cx, size_t len, Value* vec)
: JS::Rooted<ExternalValueArray>(cx, ExternalValueArray(len, vec)) {}
class AutoAssertNoPendingException {
#ifdef DEBUG
JSContext* cx_;
explicit AutoAssertNoPendingException(JSContext* cxArg) : cx_(cxArg) {
~AutoAssertNoPendingException() { MOZ_ASSERT(!JS_IsExceptionPending(cx_)); }
explicit AutoAssertNoPendingException(JSContext* cxArg) {}
class MOZ_RAII AutoNoteExclusiveDebuggerOnEval {
JSContext* cx;
Debugger* oldValue;
AutoNoteExclusiveDebuggerOnEval(JSContext* cx, Debugger* dbg)
: cx(cx), oldValue(cx->insideExclusiveDebuggerOnEval) {
cx->insideExclusiveDebuggerOnEval = dbg;
~AutoNoteExclusiveDebuggerOnEval() {
cx->insideExclusiveDebuggerOnEval = oldValue;
enum UnsafeABIStrictness {
// Should be used in functions called directly from JIT code (with
// masm.callWithABI) to assert invariants in debug builds.
// In debug mode, masm.callWithABI inserts code to verify that the
// callee function uses AutoUnsafeCallWithABI.
// While this object is live:
// 1. cx->hasAutoUnsafeCallWithABI must be true.
// 2. We can't GC.
// 3. Exceptions should not be pending/thrown.
// Note that #3 is a precaution, not a requirement. By default, we
// assert that the function is not called with a pending exception,
// and that it does not throw an exception itself.
class MOZ_RAII AutoUnsafeCallWithABI {
#ifdef DEBUG
JSContext* cx_;
bool nested_;
bool checkForPendingException_;
JS::AutoCheckCannotGC nogc;
#ifdef DEBUG
explicit AutoUnsafeCallWithABI(
UnsafeABIStrictness strictness = UnsafeABIStrictness::NoExceptions);
explicit AutoUnsafeCallWithABI(
UnsafeABIStrictness unused_ = UnsafeABIStrictness::NoExceptions) {}
} /* namespace js */
#define CHECK_THREAD(cx) \
MOZ_ASSERT_IF(cx, js::CurrentThreadCanAccessRuntime(cx->runtime()))
* [SMDOC] JS::Result transitional macros
* ## Checking Results when your return type is not Result
* This header defines alternatives to MOZ_TRY and MOZ_TRY_VAR for when you
* need to call a `Result` function from a function that uses false or nullptr
* to indicate errors:
* JS_TRY_OR_RETURN_FALSE(cx, DefenestrateObject(cx, obj));
* JS_TRY_VAR_OR_RETURN_FALSE(cx, v, GetObjectThrug(cx, obj));
* JS_TRY_VAR_OR_RETURN_NULL(cx, v, GetObjectThrug(cx, obj));
* When TRY is not what you want, because you need to do some cleanup or
* recovery on error, use this idiom:
* if (!cx->resultToBool(expr_that_is_a_Result)) {
* ... your recovery code here ...
* }
* In place of a tail call, you can use one of these methods:
* return cx->resultToBool(expr); // false on error
* return cx->resultToPtr(expr); // null on error
* Once we are using `Result` everywhere, including in public APIs, all of
* these will go away.
* JS_TRY_OR_RETURN_FALSE(cx, expr) runs expr to compute a Result value.
* On success, nothing happens; on error, it returns false immediately.
* Implementation note: this involves cx because this may eventually
* do the work of setting a pending exception or reporting OOM.
#define JS_TRY_OR_RETURN_FALSE(cx, expr) \
do { \
auto tmpResult_ = (expr); \
if (tmpResult_.isErr()) return (cx)->resultToBool(tmpResult_); \
} while (0)
#define JS_TRY_VAR_OR_RETURN_FALSE(cx, target, expr) \
do { \
auto tmpResult_ = (expr); \
if (tmpResult_.isErr()) return (cx)->resultToBool(tmpResult_); \
(target) = tmpResult_.unwrap(); \
} while (0)
#define JS_TRY_VAR_OR_RETURN_NULL(cx, target, expr) \
do { \
auto tmpResult_ = (expr); \
if (tmpResult_.isErr()) { \
MOZ_ALWAYS_FALSE((cx)->resultToBool(tmpResult_)); \
return nullptr; \
} \
(target) = tmpResult_.unwrap(); \
} while (0)
#endif /* vm_JSContext_h */