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gecko-dev/js/public/GCAPI.h

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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 http://mozilla.org/MPL/2.0/. */
/*
* High-level interface to the JS garbage collector.
*/
#ifndef js_GCAPI_h
#define js_GCAPI_h
#include "mozilla/TimeStamp.h"
#include "mozilla/Vector.h"
#include "js/GCAnnotations.h"
#include "js/TypeDecls.h"
#include "js/UniquePtr.h"
#include "js/Utility.h"
struct JSFreeOp;
#ifdef JS_BROKEN_GCC_ATTRIBUTE_WARNING
# pragma GCC diagnostic push
# pragma GCC diagnostic ignored "-Wattributes"
#endif // JS_BROKEN_GCC_ATTRIBUTE_WARNING
class JS_PUBLIC_API JSTracer;
#ifdef JS_BROKEN_GCC_ATTRIBUTE_WARNING
# pragma GCC diagnostic pop
#endif // JS_BROKEN_GCC_ATTRIBUTE_WARNING
namespace js {
namespace gc {
class GCRuntime;
} // namespace gc
namespace gcstats {
struct Statistics;
} // namespace gcstats
} // namespace js
typedef enum JSGCMode {
/** Perform only global GCs. */
JSGC_MODE_GLOBAL = 0,
/** Perform per-zone GCs until too much garbage has accumulated. */
JSGC_MODE_ZONE = 1,
/**
* Collect in short time slices rather than all at once. Implies
* JSGC_MODE_ZONE.
*/
JSGC_MODE_INCREMENTAL = 2
} JSGCMode;
/**
* Kinds of js_GC invocation.
*/
typedef enum JSGCInvocationKind {
/* Normal invocation. */
GC_NORMAL = 0,
/* Minimize GC triggers and release empty GC chunks right away. */
GC_SHRINK = 1
} JSGCInvocationKind;
typedef enum JSGCParamKey {
/**
* Maximum nominal heap before last ditch GC.
*
* Soft limit on the number of bytes we are allowed to allocate in the GC
* heap. Attempts to allocate gcthings over this limit will return null and
* subsequently invoke the standard OOM machinery, independent of available
* physical memory.
*
* Pref: javascript.options.mem.max
* Default: 0xffffffff
*/
JSGC_MAX_BYTES = 0,
/**
* Initial value for the malloc bytes threshold.
*
* Pref: javascript.options.mem.high_water_mark
* Default: TuningDefaults::MaxMallocBytes
*/
JSGC_MAX_MALLOC_BYTES = 1,
/**
* Maximum size of the generational GC nurseries.
*
* Pref: javascript.options.mem.nursery.max_kb
* Default: JS::DefaultNurseryBytes
*/
JSGC_MAX_NURSERY_BYTES = 2,
/** Amount of bytes allocated by the GC. */
JSGC_BYTES = 3,
/** Number of times GC has been invoked. Includes both major and minor GC. */
JSGC_NUMBER = 4,
/**
* Select GC mode.
*
* See: JSGCMode in GCAPI.h
* prefs: javascript.options.mem.gc_per_zone and
* javascript.options.mem.gc_incremental.
* Default: JSGC_MODE_INCREMENTAL
*/
JSGC_MODE = 6,
/** Number of cached empty GC chunks. */
JSGC_UNUSED_CHUNKS = 7,
/** Total number of allocated GC chunks. */
JSGC_TOTAL_CHUNKS = 8,
/**
* Max milliseconds to spend in an incremental GC slice.
*
* Pref: javascript.options.mem.gc_incremental_slice_ms
* Default: DefaultTimeBudget.
*/
JSGC_SLICE_TIME_BUDGET = 9,
/**
* Maximum size the GC mark stack can grow to.
*
* Pref: none
* Default: MarkStack::DefaultCapacity
*/
JSGC_MARK_STACK_LIMIT = 10,
/**
* GCs less than this far apart in time will be considered 'high-frequency
* GCs'.
*
* See setGCLastBytes in jsgc.cpp.
*
* Pref: javascript.options.mem.gc_high_frequency_time_limit_ms
* Default: HighFrequencyThreshold
*/
JSGC_HIGH_FREQUENCY_TIME_LIMIT = 11,
/**
* Start of dynamic heap growth.
*
* Pref: javascript.options.mem.gc_high_frequency_low_limit_mb
* Default: HighFrequencyLowLimitBytes
*/
JSGC_HIGH_FREQUENCY_LOW_LIMIT = 12,
/**
* End of dynamic heap growth.
*
* Pref: javascript.options.mem.gc_high_frequency_high_limit_mb
* Default: HighFrequencyHighLimitBytes
*/
JSGC_HIGH_FREQUENCY_HIGH_LIMIT = 13,
/**
* Upper bound of heap growth.
*
* Pref: javascript.options.mem.gc_high_frequency_heap_growth_max
* Default: HighFrequencyHeapGrowthMax
*/
JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MAX = 14,
/**
* Lower bound of heap growth.
*
* Pref: javascript.options.mem.gc_high_frequency_heap_growth_min
* Default: HighFrequencyHeapGrowthMin
*/
JSGC_HIGH_FREQUENCY_HEAP_GROWTH_MIN = 15,
/**
* Heap growth for low frequency GCs.
*
* Pref: javascript.options.mem.gc_low_frequency_heap_growth
* Default: LowFrequencyHeapGrowth
*/
JSGC_LOW_FREQUENCY_HEAP_GROWTH = 16,
/**
* If false, the heap growth factor is fixed at 3. If true, it is determined
* based on whether GCs are high- or low- frequency.
*
* Pref: javascript.options.mem.gc_dynamic_heap_growth
* Default: DynamicHeapGrowthEnabled
*/
JSGC_DYNAMIC_HEAP_GROWTH = 17,
/**
* If true, high-frequency GCs will use a longer mark slice.
*
* Pref: javascript.options.mem.gc_dynamic_mark_slice
* Default: DynamicMarkSliceEnabled
*/
JSGC_DYNAMIC_MARK_SLICE = 18,
/**
* Lower limit after which we limit the heap growth.
*
* The base value used to compute zone->threshold.gcTriggerBytes(). When
* usage.gcBytes() surpasses threshold.gcTriggerBytes() for a zone, the
* zone may be scheduled for a GC, depending on the exact circumstances.
*
* Pref: javascript.options.mem.gc_allocation_threshold_mb
* Default GCZoneAllocThresholdBase
*/
JSGC_ALLOCATION_THRESHOLD = 19,
/**
* We try to keep at least this many unused chunks in the free chunk pool at
* all times, even after a shrinking GC.
*
* Pref: javascript.options.mem.gc_min_empty_chunk_count
* Default: MinEmptyChunkCount
*/
JSGC_MIN_EMPTY_CHUNK_COUNT = 21,
/**
* We never keep more than this many unused chunks in the free chunk
* pool.
*
* Pref: javascript.options.mem.gc_min_empty_chunk_count
* Default: MinEmptyChunkCount
*/
JSGC_MAX_EMPTY_CHUNK_COUNT = 22,
/**
* Whether compacting GC is enabled.
*
* Pref: javascript.options.mem.gc_compacting
* Default: CompactingEnabled
*/
JSGC_COMPACTING_ENABLED = 23,
/**
* Factor for triggering a GC based on JSGC_ALLOCATION_THRESHOLD
*
* Default: ZoneAllocThresholdFactorDefault
* Pref: None
*/
JSGC_ALLOCATION_THRESHOLD_FACTOR = 25,
/**
* Factor for triggering a GC based on JSGC_ALLOCATION_THRESHOLD.
* Used if another GC (in different zones) is already running.
*
* Default: ZoneAllocThresholdFactorAvoidInterruptDefault
* Pref: None
*/
JSGC_ALLOCATION_THRESHOLD_FACTOR_AVOID_INTERRUPT = 26,
/**
* Attempt to run a minor GC in the idle time if the free space falls
* below this threshold.
*
* Default: NurseryChunkUsableSize / 4
* Pref: None
*/
JSGC_NURSERY_FREE_THRESHOLD_FOR_IDLE_COLLECTION = 27,
/**
* If this percentage of the nursery is tenured, then proceed to examine which
* groups we should pretenure.
*
* Default: PretenureThreshold
* Pref: None
*/
JSGC_PRETENURE_THRESHOLD = 28,
/**
* If the above condition is met, then any object group that tenures more than
* this number of objects will be pretenured (if it can be).
*
* Default: PretenureGroupThreshold
* Pref: None
*/
JSGC_PRETENURE_GROUP_THRESHOLD = 29,
} JSGCParamKey;
/*
* Generic trace operation that calls JS::TraceEdge on each traceable thing's
* location reachable from data.
*/
typedef void (*JSTraceDataOp)(JSTracer* trc, void* data);
typedef enum JSGCStatus { JSGC_BEGIN, JSGC_END } JSGCStatus;
typedef void (*JSGCCallback)(JSContext* cx, JSGCStatus status, void* data);
typedef void (*JSObjectsTenuredCallback)(JSContext* cx, void* data);
typedef enum JSFinalizeStatus {
/**
* Called when preparing to sweep a group of zones, before anything has been
* swept. The collector will not yield to the mutator before calling the
* callback with JSFINALIZE_GROUP_START status.
*/
JSFINALIZE_GROUP_PREPARE,
/**
* Called after preparing to sweep a group of zones. Weak references to
* unmarked things have been removed at this point, but no GC things have
* been swept. The collector may yield to the mutator after this point.
*/
JSFINALIZE_GROUP_START,
/**
* Called after sweeping a group of zones. All dead GC things have been
* swept at this point.
*/
JSFINALIZE_GROUP_END,
/**
* Called at the end of collection when everything has been swept.
*/
JSFINALIZE_COLLECTION_END
} JSFinalizeStatus;
typedef void (*JSFinalizeCallback)(JSFreeOp* fop, JSFinalizeStatus status,
void* data);
typedef void (*JSWeakPointerZonesCallback)(JSContext* cx, void* data);
typedef void (*JSWeakPointerCompartmentCallback)(JSContext* cx,
JS::Compartment* comp,
void* data);
/**
* Finalizes external strings created by JS_NewExternalString. The finalizer
* can be called off the main thread.
*/
struct JSStringFinalizer {
void (*finalize)(const JSStringFinalizer* fin, char16_t* chars);
};
namespace JS {
#define GCREASONS(D) \
/* Reasons internal to the JS engine */ \
D(API, 0) \
D(EAGER_ALLOC_TRIGGER, 1) \
D(DESTROY_RUNTIME, 2) \
D(ROOTS_REMOVED, 3) \
D(LAST_DITCH, 4) \
D(TOO_MUCH_MALLOC, 5) \
D(ALLOC_TRIGGER, 6) \
D(DEBUG_GC, 7) \
D(COMPARTMENT_REVIVED, 8) \
D(RESET, 9) \
D(OUT_OF_NURSERY, 10) \
D(EVICT_NURSERY, 11) \
D(DELAYED_ATOMS_GC, 12) \
D(SHARED_MEMORY_LIMIT, 13) \
D(IDLE_TIME_COLLECTION, 14) \
D(INCREMENTAL_TOO_SLOW, 15) \
D(ABORT_GC, 16) \
D(FULL_WHOLE_CELL_BUFFER, 17) \
D(FULL_GENERIC_BUFFER, 18) \
D(FULL_VALUE_BUFFER, 19) \
D(FULL_CELL_PTR_BUFFER, 20) \
D(FULL_SLOT_BUFFER, 21) \
D(FULL_SHAPE_BUFFER, 22) \
D(TOO_MUCH_WASM_MEMORY, 23) \
D(DISABLE_GENERATIONAL_GC, 24) \
D(FINISH_GC, 25) \
D(PREPARE_FOR_TRACING, 26) \
\
/* These are reserved for future use. */ \
D(RESERVED3, 27) \
D(RESERVED4, 28) \
D(RESERVED5, 29) \
D(RESERVED6, 30) \
D(RESERVED7, 31) \
D(RESERVED8, 32) \
\
/* Reasons from Firefox */ \
D(DOM_WINDOW_UTILS, 33) \
D(COMPONENT_UTILS, 34) \
D(MEM_PRESSURE, 35) \
D(CC_WAITING, 36) \
D(CC_FORCED, 37) \
D(LOAD_END, 38) \
D(UNUSED3, 39) \
D(PAGE_HIDE, 40) \
D(NSJSCONTEXT_DESTROY, 41) \
D(WORKER_SHUTDOWN, 42) \
D(SET_DOC_SHELL, 43) \
D(DOM_UTILS, 44) \
D(DOM_IPC, 45) \
D(DOM_WORKER, 46) \
D(INTER_SLICE_GC, 47) \
D(UNUSED1, 48) \
D(FULL_GC_TIMER, 49) \
D(SHUTDOWN_CC, 50) \
D(UNUSED2, 51) \
D(USER_INACTIVE, 52) \
D(XPCONNECT_SHUTDOWN, 53) \
D(DOCSHELL, 54) \
D(HTML_PARSER, 55)
enum class GCReason {
#define MAKE_REASON(name, val) name = val,
GCREASONS(MAKE_REASON)
#undef MAKE_REASON
NO_REASON,
NUM_REASONS,
/*
* For telemetry, we want to keep a fixed max bucket size over time so we
* don't have to switch histograms. 100 is conservative; but the cost of extra
* buckets seems to be low while the cost of switching histograms is high.
*/
NUM_TELEMETRY_REASONS = 100
};
/**
* Get a statically allocated C string explaining the given GC reason.
*/
extern JS_PUBLIC_API const char* ExplainGCReason(JS::GCReason reason);
/*
* Zone GC:
*
* SpiderMonkey's GC is capable of performing a collection on an arbitrary
* subset of the zones in the system. This allows an embedding to minimize
* collection time by only collecting zones that have run code recently,
* ignoring the parts of the heap that are unlikely to have changed.
*
* When triggering a GC using one of the functions below, it is first necessary
* to select the zones to be collected. To do this, you can call
* PrepareZoneForGC on each zone, or you can call PrepareForFullGC to select
* all zones. Failing to select any zone is an error.
*/
/**
* Schedule the given zone to be collected as part of the next GC.
*/
extern JS_PUBLIC_API void PrepareZoneForGC(Zone* zone);
/**
* Schedule all zones to be collected in the next GC.
*/
extern JS_PUBLIC_API void PrepareForFullGC(JSContext* cx);
/**
* When performing an incremental GC, the zones that were selected for the
* previous incremental slice must be selected in subsequent slices as well.
* This function selects those slices automatically.
*/
extern JS_PUBLIC_API void PrepareForIncrementalGC(JSContext* cx);
/**
* Returns true if any zone in the system has been scheduled for GC with one of
* the functions above or by the JS engine.
*/
extern JS_PUBLIC_API bool IsGCScheduled(JSContext* cx);
/**
* Undoes the effect of the Prepare methods above. The given zone will not be
* collected in the next GC.
*/
extern JS_PUBLIC_API void SkipZoneForGC(Zone* zone);
/*
* Non-Incremental GC:
*
* The following functions perform a non-incremental GC.
*/
/**
* Performs a non-incremental collection of all selected zones.
*
* If the gckind argument is GC_NORMAL, then some objects that are unreachable
* from the program may still be alive afterwards because of internal
* references; if GC_SHRINK is passed then caches and other temporary references
* to objects will be cleared and all unreferenced objects will be removed from
* the system.
*/
extern JS_PUBLIC_API void NonIncrementalGC(JSContext* cx,
JSGCInvocationKind gckind,
GCReason reason);
/*
* Incremental GC:
*
* Incremental GC divides the full mark-and-sweep collection into multiple
* slices, allowing client JavaScript code to run between each slice. This
* allows interactive apps to avoid long collection pauses. Incremental GC does
* not make collection take less time, it merely spreads that time out so that
* the pauses are less noticable.
*
* For a collection to be carried out incrementally the following conditions
* must be met:
* - The collection must be run by calling JS::IncrementalGC() rather than
* JS_GC().
* - The GC mode must have been set to JSGC_MODE_INCREMENTAL with
* JS_SetGCParameter().
*
* Note: Even if incremental GC is enabled and working correctly,
* non-incremental collections can still happen when low on memory.
*/
/**
* Begin an incremental collection and perform one slice worth of work. When
* this function returns, the collection may not be complete.
* IncrementalGCSlice() must be called repeatedly until
* !IsIncrementalGCInProgress(cx).
*
* Note: SpiderMonkey's GC is not realtime. Slices in practice may be longer or
* shorter than the requested interval.
*/
extern JS_PUBLIC_API void StartIncrementalGC(JSContext* cx,
JSGCInvocationKind gckind,
GCReason reason,
int64_t millis = 0);
/**
* Perform a slice of an ongoing incremental collection. When this function
* returns, the collection may not be complete. It must be called repeatedly
* until !IsIncrementalGCInProgress(cx).
*
* Note: SpiderMonkey's GC is not realtime. Slices in practice may be longer or
* shorter than the requested interval.
*/
extern JS_PUBLIC_API void IncrementalGCSlice(JSContext* cx, GCReason reason,
int64_t millis = 0);
/**
* If IsIncrementalGCInProgress(cx), this call finishes the ongoing collection
* by performing an arbitrarily long slice. If !IsIncrementalGCInProgress(cx),
* this is equivalent to NonIncrementalGC. When this function returns,
* IsIncrementalGCInProgress(cx) will always be false.
*/
extern JS_PUBLIC_API void FinishIncrementalGC(JSContext* cx, GCReason reason);
/**
* If IsIncrementalGCInProgress(cx), this call aborts the ongoing collection and
* performs whatever work needs to be done to return the collector to its idle
* state. This may take an arbitrarily long time. When this function returns,
* IsIncrementalGCInProgress(cx) will always be false.
*/
extern JS_PUBLIC_API void AbortIncrementalGC(JSContext* cx);
namespace dbg {
// The `JS::dbg::GarbageCollectionEvent` class is essentially a view of the
// `js::gcstats::Statistics` data without the uber implementation-specific bits.
// It should generally be palatable for web developers.
class GarbageCollectionEvent {
// The major GC number of the GC cycle this data pertains to.
uint64_t majorGCNumber_;
// Reference to a non-owned, statically allocated C string. This is a very
// short reason explaining why a GC was triggered.
const char* reason;
// Reference to a nullable, non-owned, statically allocated C string. If the
// collection was forced to be non-incremental, this is a short reason of
// why the GC could not perform an incremental collection.
const char* nonincrementalReason;
// Represents a single slice of a possibly multi-slice incremental garbage
// collection.
struct Collection {
mozilla::TimeStamp startTimestamp;
mozilla::TimeStamp endTimestamp;
};
// The set of garbage collection slices that made up this GC cycle.
mozilla::Vector<Collection> collections;
GarbageCollectionEvent(const GarbageCollectionEvent& rhs) = delete;
GarbageCollectionEvent& operator=(const GarbageCollectionEvent& rhs) = delete;
public:
explicit GarbageCollectionEvent(uint64_t majorGCNum)
: majorGCNumber_(majorGCNum),
reason(nullptr),
nonincrementalReason(nullptr),
collections() {}
using Ptr = js::UniquePtr<GarbageCollectionEvent>;
static Ptr Create(JSRuntime* rt, ::js::gcstats::Statistics& stats,
uint64_t majorGCNumber);
JSObject* toJSObject(JSContext* cx) const;
uint64_t majorGCNumber() const { return majorGCNumber_; }
};
} // namespace dbg
enum GCProgress {
/*
* During GC, the GC is bracketed by GC_CYCLE_BEGIN/END callbacks. Each
* slice between those (whether an incremental or the sole non-incremental
* slice) is bracketed by GC_SLICE_BEGIN/GC_SLICE_END.
*/
GC_CYCLE_BEGIN,
GC_SLICE_BEGIN,
GC_SLICE_END,
GC_CYCLE_END
};
struct JS_PUBLIC_API GCDescription {
bool isZone_;
bool isComplete_;
JSGCInvocationKind invocationKind_;
GCReason reason_;
GCDescription(bool isZone, bool isComplete, JSGCInvocationKind kind,
GCReason reason)
: isZone_(isZone),
isComplete_(isComplete),
invocationKind_(kind),
reason_(reason) {}
char16_t* formatSliceMessage(JSContext* cx) const;
char16_t* formatSummaryMessage(JSContext* cx) const;
mozilla::TimeStamp startTime(JSContext* cx) const;
mozilla::TimeStamp endTime(JSContext* cx) const;
mozilla::TimeStamp lastSliceStart(JSContext* cx) const;
mozilla::TimeStamp lastSliceEnd(JSContext* cx) const;
char16_t* formatJSONTelemetry(JSContext* cx, uint64_t timestamp) const;
JS::UniqueChars sliceToJSONProfiler(JSContext* cx) const;
JS::UniqueChars formatJSONProfiler(JSContext* cx) const;
JS::dbg::GarbageCollectionEvent::Ptr toGCEvent(JSContext* cx) const;
};
extern JS_PUBLIC_API UniqueChars MinorGcToJSON(JSContext* cx);
typedef void (*GCSliceCallback)(JSContext* cx, GCProgress progress,
const GCDescription& desc);
/**
* The GC slice callback is called at the beginning and end of each slice. This
* callback may be used for GC notifications as well as to perform additional
* marking.
*/
extern JS_PUBLIC_API GCSliceCallback
SetGCSliceCallback(JSContext* cx, GCSliceCallback callback);
/**
* Describes the progress of an observed nursery collection.
*/
enum class GCNurseryProgress {
/**
* The nursery collection is starting.
*/
GC_NURSERY_COLLECTION_START,
/**
* The nursery collection is ending.
*/
GC_NURSERY_COLLECTION_END
};
/**
* A nursery collection callback receives the progress of the nursery collection
* and the reason for the collection.
*/
using GCNurseryCollectionCallback = void (*)(JSContext* cx,
GCNurseryProgress progress,
GCReason reason);
/**
* Set the nursery collection callback for the given runtime. When set, it will
* be called at the start and end of every nursery collection.
*/
extern JS_PUBLIC_API GCNurseryCollectionCallback SetGCNurseryCollectionCallback(
JSContext* cx, GCNurseryCollectionCallback callback);
typedef void (*DoCycleCollectionCallback)(JSContext* cx);
/**
* The purge gray callback is called after any COMPARTMENT_REVIVED GC in which
* the majority of compartments have been marked gray.
*/
extern JS_PUBLIC_API DoCycleCollectionCallback
SetDoCycleCollectionCallback(JSContext* cx, DoCycleCollectionCallback callback);
/**
* Incremental GC defaults to enabled, but may be disabled for testing or in
* embeddings that have not yet implemented barriers on their native classes.
* There is not currently a way to re-enable incremental GC once it has been
* disabled on the runtime.
*/
extern JS_PUBLIC_API void DisableIncrementalGC(JSContext* cx);
/**
* Returns true if incremental GC is enabled. Simply having incremental GC
* enabled is not sufficient to ensure incremental collections are happening.
* See the comment "Incremental GC" above for reasons why incremental GC may be
* suppressed. Inspection of the "nonincremental reason" field of the
* GCDescription returned by GCSliceCallback may help narrow down the cause if
* collections are not happening incrementally when expected.
*/
extern JS_PUBLIC_API bool IsIncrementalGCEnabled(JSContext* cx);
/**
* Returns true while an incremental GC is ongoing, both when actively
* collecting and between slices.
*/
extern JS_PUBLIC_API bool IsIncrementalGCInProgress(JSContext* cx);
/**
* Returns true while an incremental GC is ongoing, both when actively
* collecting and between slices.
*/
extern JS_PUBLIC_API bool IsIncrementalGCInProgress(JSRuntime* rt);
/**
* Returns true if the most recent GC ran incrementally.
*/
extern JS_PUBLIC_API bool WasIncrementalGC(JSRuntime* rt);
/*
* Generational GC:
*
* Note: Generational GC is not yet enabled by default. The following class
* is non-functional unless SpiderMonkey was configured with
* --enable-gcgenerational.
*/
/** Ensure that generational GC is disabled within some scope. */
class JS_PUBLIC_API AutoDisableGenerationalGC {
JSContext* cx;
public:
explicit AutoDisableGenerationalGC(JSContext* cx);
~AutoDisableGenerationalGC();
};
/**
* Returns true if generational allocation and collection is currently enabled
* on the given runtime.
*/
extern JS_PUBLIC_API bool IsGenerationalGCEnabled(JSRuntime* rt);
/**
* Pass a subclass of this "abstract" class to callees to require that they
* never GC. Subclasses can use assertions or the hazard analysis to ensure no
* GC happens.
*/
class JS_PUBLIC_API AutoRequireNoGC {
protected:
AutoRequireNoGC() {}
~AutoRequireNoGC() {}
};
/**
* Diagnostic assert (see MOZ_DIAGNOSTIC_ASSERT) that GC cannot occur while this
* class is live. This class does not disable the static rooting hazard
* analysis.
*
* This works by entering a GC unsafe region, which is checked on allocation and
* on GC.
*/
class JS_PUBLIC_API AutoAssertNoGC : public AutoRequireNoGC {
#ifdef MOZ_DIAGNOSTIC_ASSERT_ENABLED
JSContext* cx_;
public:
// This gets the context from TLS if it is not passed in.
explicit AutoAssertNoGC(JSContext* cx = nullptr);
~AutoAssertNoGC();
#else
public:
explicit AutoAssertNoGC(JSContext* cx = nullptr) {}
~AutoAssertNoGC() {}
#endif
};
/**
* Disable the static rooting hazard analysis in the live region and assert in
* debug builds if any allocation that could potentially trigger a GC occurs
* while this guard object is live. This is most useful to help the exact
* rooting hazard analysis in complex regions, since it cannot understand
* dataflow.
*
* Note: GC behavior is unpredictable even when deterministic and is generally
* non-deterministic in practice. The fact that this guard has not
* asserted is not a guarantee that a GC cannot happen in the guarded
* region. As a rule, anyone performing a GC unsafe action should
* understand the GC properties of all code in that region and ensure
* that the hazard analysis is correct for that code, rather than relying
* on this class.
*/
#ifdef DEBUG
class JS_PUBLIC_API AutoSuppressGCAnalysis : public AutoAssertNoGC {
public:
explicit AutoSuppressGCAnalysis(JSContext* cx = nullptr)
: AutoAssertNoGC(cx) {}
} JS_HAZ_GC_SUPPRESSED;
#else
class JS_PUBLIC_API AutoSuppressGCAnalysis : public AutoRequireNoGC {
public:
explicit AutoSuppressGCAnalysis(JSContext* cx = nullptr) {}
} JS_HAZ_GC_SUPPRESSED;
#endif
/**
* Assert that code is only ever called from a GC callback, disable the static
* rooting hazard analysis and assert if any allocation that could potentially
* trigger a GC occurs while this guard object is live.
*
* This is useful to make the static analysis ignore code that runs in GC
* callbacks.
*/
class JS_PUBLIC_API AutoAssertGCCallback : public AutoSuppressGCAnalysis {
public:
#ifdef DEBUG
AutoAssertGCCallback();
#else
AutoAssertGCCallback() {}
#endif
};
/**
* Place AutoCheckCannotGC in scopes that you believe can never GC. These
* annotations will be verified both dynamically via AutoAssertNoGC, and
* statically with the rooting hazard analysis (implemented by making the
* analysis consider AutoCheckCannotGC to be a GC pointer, and therefore
* complain if it is live across a GC call.) It is useful when dealing with
* internal pointers to GC things where the GC thing itself may not be present
* for the static analysis: e.g. acquiring inline chars from a JSString* on the
* heap.
*
* We only do the assertion checking in DEBUG builds.
*/
#ifdef DEBUG
class JS_PUBLIC_API AutoCheckCannotGC : public AutoAssertNoGC {
public:
explicit AutoCheckCannotGC(JSContext* cx = nullptr) : AutoAssertNoGC(cx) {}
} JS_HAZ_GC_INVALIDATED;
#else
class JS_PUBLIC_API AutoCheckCannotGC : public AutoRequireNoGC {
public:
explicit AutoCheckCannotGC(JSContext* cx = nullptr) {}
} JS_HAZ_GC_INVALIDATED;
#endif
/*
* Internal to Firefox.
*/
extern JS_FRIEND_API void NotifyGCRootsRemoved(JSContext* cx);
} /* namespace JS */
/**
* Register externally maintained GC roots.
*
* traceOp: the trace operation. For each root the implementation should call
* JS::TraceEdge whenever the root contains a traceable thing.
* data: the data argument to pass to each invocation of traceOp.
*/
extern JS_PUBLIC_API bool JS_AddExtraGCRootsTracer(JSContext* cx,
JSTraceDataOp traceOp,
void* data);
/** Undo a call to JS_AddExtraGCRootsTracer. */
extern JS_PUBLIC_API void JS_RemoveExtraGCRootsTracer(JSContext* cx,
JSTraceDataOp traceOp,
void* data);
extern JS_PUBLIC_API void JS_GC(JSContext* cx,
JS::GCReason reason = JS::GCReason::API);
extern JS_PUBLIC_API void JS_MaybeGC(JSContext* cx);
extern JS_PUBLIC_API void JS_SetGCCallback(JSContext* cx, JSGCCallback cb,
void* data);
extern JS_PUBLIC_API void JS_SetObjectsTenuredCallback(
JSContext* cx, JSObjectsTenuredCallback cb, void* data);
extern JS_PUBLIC_API bool JS_AddFinalizeCallback(JSContext* cx,
JSFinalizeCallback cb,
void* data);
extern JS_PUBLIC_API void JS_RemoveFinalizeCallback(JSContext* cx,
JSFinalizeCallback cb);
/*
* Weak pointers and garbage collection
*
* Weak pointers are by their nature not marked as part of garbage collection,
* but they may need to be updated in two cases after a GC:
*
* 1) Their referent was found not to be live and is about to be finalized
* 2) Their referent has been moved by a compacting GC
*
* To handle this, any part of the system that maintain weak pointers to
* JavaScript GC things must register a callback with
* JS_(Add,Remove)WeakPointer{ZoneGroup,Compartment}Callback(). This callback
* must then call JS_UpdateWeakPointerAfterGC() on all weak pointers it knows
* about.
*
* Since sweeping is incremental, we have several callbacks to avoid repeatedly
* having to visit all embedder structures. The WeakPointerZonesCallback is
* called once for each strongly connected group of zones, whereas the
* WeakPointerCompartmentCallback is called once for each compartment that is
* visited while sweeping. Structures that cannot contain references in more
* than one compartment should sweep the relevant per-compartment structures
* using the latter callback to minimizer per-slice overhead.
*
* The argument to JS_UpdateWeakPointerAfterGC() is an in-out param. If the
* referent is about to be finalized the pointer will be set to null. If the
* referent has been moved then the pointer will be updated to point to the new
* location.
*
* Callers of this method are responsible for updating any state that is
* dependent on the object's address. For example, if the object's address is
* used as a key in a hashtable, then the object must be removed and
* re-inserted with the correct hash.
*/
extern JS_PUBLIC_API bool JS_AddWeakPointerZonesCallback(
JSContext* cx, JSWeakPointerZonesCallback cb, void* data);
extern JS_PUBLIC_API void JS_RemoveWeakPointerZonesCallback(
JSContext* cx, JSWeakPointerZonesCallback cb);
extern JS_PUBLIC_API bool JS_AddWeakPointerCompartmentCallback(
JSContext* cx, JSWeakPointerCompartmentCallback cb, void* data);
extern JS_PUBLIC_API void JS_RemoveWeakPointerCompartmentCallback(
JSContext* cx, JSWeakPointerCompartmentCallback cb);
namespace JS {
template <typename T>
class Heap;
}
extern JS_PUBLIC_API void JS_UpdateWeakPointerAfterGC(
JS::Heap<JSObject*>* objp);
extern JS_PUBLIC_API void JS_UpdateWeakPointerAfterGCUnbarriered(
JSObject** objp);
extern JS_PUBLIC_API void JS_SetGCParameter(JSContext* cx, JSGCParamKey key,
uint32_t value);
extern JS_PUBLIC_API void JS_ResetGCParameter(JSContext* cx, JSGCParamKey key);
extern JS_PUBLIC_API uint32_t JS_GetGCParameter(JSContext* cx,
JSGCParamKey key);
extern JS_PUBLIC_API void JS_SetGCParametersBasedOnAvailableMemory(
JSContext* cx, uint32_t availMem);
/**
* Create a new JSString whose chars member refers to external memory, i.e.,
* memory requiring application-specific finalization.
*/
extern JS_PUBLIC_API JSString* JS_NewExternalString(
JSContext* cx, const char16_t* chars, size_t length,
const JSStringFinalizer* fin);
/**
* Create a new JSString whose chars member may refer to external memory.
* If a new external string is allocated, |*allocatedExternal| is set to true.
* Otherwise the returned string is either not an external string or an
* external string allocated by a previous call and |*allocatedExternal| is set
* to false. If |*allocatedExternal| is false, |fin| won't be called.
*/
extern JS_PUBLIC_API JSString* JS_NewMaybeExternalString(
JSContext* cx, const char16_t* chars, size_t length,
const JSStringFinalizer* fin, bool* allocatedExternal);
/**
* Return whether 'str' was created with JS_NewExternalString or
* JS_NewExternalStringWithClosure.
*/
extern JS_PUBLIC_API bool JS_IsExternalString(JSString* str);
/**
* Return the 'fin' arg passed to JS_NewExternalString.
*/
extern JS_PUBLIC_API const JSStringFinalizer* JS_GetExternalStringFinalizer(
JSString* str);
namespace JS {
extern JS_PUBLIC_API bool IsIdleGCTaskNeeded(JSRuntime* rt);
extern JS_PUBLIC_API void RunIdleTimeGCTask(JSRuntime* rt);
} // namespace JS
namespace js {
namespace gc {
/**
* Create an object providing access to the garbage collector's internal notion
* of the current state of memory (both GC heap memory and GCthing-controlled
* malloc memory.
*/
extern JS_PUBLIC_API JSObject* NewMemoryInfoObject(JSContext* cx);
} /* namespace gc */
} /* namespace js */
#endif /* js_GCAPI_h */
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