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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/. */
#ifndef js_RootingAPI_h
#define js_RootingAPI_h
#include "mozilla/Attributes.h"
#include "mozilla/DebugOnly.h"
#include "mozilla/EnumeratedArray.h"
#include "mozilla/LinkedList.h"
#include "mozilla/Maybe.h"
#include <type_traits>
#include <utility>
#include "jspubtd.h"
#include "js/ComparisonOperators.h" // JS::detail::DefineComparisonOps
#include "js/GCAnnotations.h"
#include "js/GCPolicyAPI.h"
#include "js/GCTypeMacros.h" // JS_FOR_EACH_PUBLIC_{,TAGGED_}GC_POINTER_TYPE
#include "js/HashTable.h"
#include "js/HeapAPI.h"
#include "js/ProfilingStack.h"
#include "js/Realm.h"
#include "js/TypeDecls.h"
#include "js/UniquePtr.h"
/*
* [SMDOC] Stack Rooting
*
* Moving GC Stack Rooting
*
* A moving GC may change the physical location of GC allocated things, even
* when they are rooted, updating all pointers to the thing to refer to its new
* location. The GC must therefore know about all live pointers to a thing,
* not just one of them, in order to behave correctly.
*
* The |Rooted| and |Handle| classes below are used to root stack locations
* whose value may be held live across a call that can trigger GC. For a
* code fragment such as:
*
* JSObject* obj = NewObject(cx);
* DoSomething(cx);
* ... = obj->lastProperty();
*
* If |DoSomething()| can trigger a GC, the stack location of |obj| must be
* rooted to ensure that the GC does not move the JSObject referred to by
* |obj| without updating |obj|'s location itself. This rooting must happen
* regardless of whether there are other roots which ensure that the object
* itself will not be collected.
*
* If |DoSomething()| cannot trigger a GC, and the same holds for all other
* calls made between |obj|'s definitions and its last uses, then no rooting
* is required.
*
* SpiderMonkey can trigger a GC at almost any time and in ways that are not
* always clear. For example, the following innocuous-looking actions can
* cause a GC: allocation of any new GC thing; JSObject::hasProperty;
* JS_ReportError and friends; and ToNumber, among many others. The following
* dangerous-looking actions cannot trigger a GC: js_malloc, cx->malloc_,
* rt->malloc_, and friends and JS_ReportOutOfMemory.
*
* The following family of three classes will exactly root a stack location.
* Incorrect usage of these classes will result in a compile error in almost
* all cases. Therefore, it is very hard to be incorrectly rooted if you use
* these classes exclusively. These classes are all templated on the type T of
* the value being rooted.
*
* - Rooted<T> declares a variable of type T, whose value is always rooted.
* Rooted<T> may be automatically coerced to a Handle<T>, below. Rooted<T>
* should be used whenever a local variable's value may be held live across a
* call which can trigger a GC.
*
* - Handle<T> is a const reference to a Rooted<T>. Functions which take GC
* things or values as arguments and need to root those arguments should
* generally use handles for those arguments and avoid any explicit rooting.
* This has two benefits. First, when several such functions call each other
* then redundant rooting of multiple copies of the GC thing can be avoided.
* Second, if the caller does not pass a rooted value a compile error will be
* generated, which is quicker and easier to fix than when relying on a
* separate rooting analysis.
*
* - MutableHandle<T> is a non-const reference to Rooted<T>. It is used in the
* same way as Handle<T> and includes a |set(const T& v)| method to allow
* updating the value of the referenced Rooted<T>. A MutableHandle<T> can be
* created with an implicit cast from a Rooted<T>*.
*
* In some cases the small performance overhead of exact rooting (measured to
* be a few nanoseconds on desktop) is too much. In these cases, try the
* following:
*
* - Move all Rooted<T> above inner loops: this allows you to re-use the root
* on each iteration of the loop.
*
* - Pass Handle<T> through your hot call stack to avoid re-rooting costs at
* every invocation.
*
* The following diagram explains the list of supported, implicit type
* conversions between classes of this family:
*
* Rooted<T> ----> Handle<T>
* | ^
* | |
* | |
* +---> MutableHandle<T>
* (via &)
*
* All of these types have an implicit conversion to raw pointers.
*/
namespace js {
template <typename T>
struct BarrierMethods {};
template <typename Element, typename Wrapper>
class WrappedPtrOperations {};
template <typename Element, typename Wrapper>
class MutableWrappedPtrOperations
: public WrappedPtrOperations<Element, Wrapper> {};
template <typename T, typename Wrapper>
class RootedBase : public MutableWrappedPtrOperations<T, Wrapper> {};
template <typename T, typename Wrapper>
class HandleBase : public WrappedPtrOperations<T, Wrapper> {};
template <typename T, typename Wrapper>
class MutableHandleBase : public MutableWrappedPtrOperations<T, Wrapper> {};
template <typename T, typename Wrapper>
class HeapBase : public MutableWrappedPtrOperations<T, Wrapper> {};
// Cannot use FOR_EACH_HEAP_ABLE_GC_POINTER_TYPE, as this would import too many
// macros into scope
template <typename T>
struct IsHeapConstructibleType {
static constexpr bool value = false;
};
#define DECLARE_IS_HEAP_CONSTRUCTIBLE_TYPE(T) \
template <> \
struct IsHeapConstructibleType<T> { \
static constexpr bool value = true; \
};
JS_FOR_EACH_PUBLIC_GC_POINTER_TYPE(DECLARE_IS_HEAP_CONSTRUCTIBLE_TYPE)
JS_FOR_EACH_PUBLIC_TAGGED_GC_POINTER_TYPE(DECLARE_IS_HEAP_CONSTRUCTIBLE_TYPE)
#undef DECLARE_IS_HEAP_CONSTRUCTIBLE_TYPE
template <typename T, typename Wrapper>
class PersistentRootedBase : public MutableWrappedPtrOperations<T, Wrapper> {};
namespace gc {
struct Cell;
template <typename T>
struct PersistentRootedMarker;
} /* namespace gc */
// Important: Return a reference so passing a Rooted<T>, etc. to
// something that takes a |const T&| is not a GC hazard.
#define DECLARE_POINTER_CONSTREF_OPS(T) \
operator const T&() const { return get(); } \
const T& operator->() const { return get(); }
// Assignment operators on a base class are hidden by the implicitly defined
// operator= on the derived class. Thus, define the operator= directly on the
// class as we would need to manually pass it through anyway.
#define DECLARE_POINTER_ASSIGN_OPS(Wrapper, T) \
Wrapper<T>& operator=(const T& p) { \
set(p); \
return *this; \
} \
Wrapper<T>& operator=(T&& p) { \
set(std::move(p)); \
return *this; \
} \
Wrapper<T>& operator=(const Wrapper<T>& other) { \
set(other.get()); \
return *this; \
}
#define DELETE_ASSIGNMENT_OPS(Wrapper, T) \
template <typename S> \
Wrapper<T>& operator=(S) = delete; \
Wrapper<T>& operator=(const Wrapper<T>&) = delete;
#define DECLARE_NONPOINTER_ACCESSOR_METHODS(ptr) \
const T* address() const { return &(ptr); } \
const T& get() const { return (ptr); }
#define DECLARE_NONPOINTER_MUTABLE_ACCESSOR_METHODS(ptr) \
T* address() { return &(ptr); } \
T& get() { return (ptr); }
} /* namespace js */
namespace JS {
JS_FRIEND_API void HeapObjectPostWriteBarrier(JSObject** objp, JSObject* prev,
JSObject* next);
JS_FRIEND_API void HeapStringPostWriteBarrier(JSString** objp, JSString* prev,
JSString* next);
JS_FRIEND_API void HeapBigIntPostWriteBarrier(JS::BigInt** bip,
JS::BigInt* prev,
JS::BigInt* next);
JS_FRIEND_API void HeapObjectWriteBarriers(JSObject** objp, JSObject* prev,
JSObject* next);
JS_FRIEND_API void HeapStringWriteBarriers(JSString** objp, JSString* prev,
JSString* next);
JS_FRIEND_API void HeapBigIntWriteBarriers(JS::BigInt** bip, JS::BigInt* prev,
JS::BigInt* next);
JS_FRIEND_API void HeapScriptWriteBarriers(JSScript** objp, JSScript* prev,
JSScript* next);
/**
* Create a safely-initialized |T|, suitable for use as a default value in
* situations requiring a safe but arbitrary |T| value.
*/
template <typename T>
inline T SafelyInitialized() {
// This function wants to presume that |T()| -- which value-initializes a
// |T| per C++11 [expr.type.conv]p2 -- will produce a safely-initialized,
// safely-usable T that it can return.
#if defined(XP_WIN) || defined(XP_MACOSX) || \
(defined(XP_UNIX) && !defined(__clang__))
// That presumption holds for pointers, where value initialization produces
// a null pointer.
constexpr bool IsPointer = std::is_pointer_v<T>;
// For classes and unions we *assume* that if |T|'s default constructor is
// non-trivial it'll initialize correctly. (This is unideal, but C++
// doesn't offer a type trait indicating whether a class's constructor is
// user-defined, which better approximates our desired semantics.)
constexpr bool IsNonTriviallyDefaultConstructibleClassOrUnion =
(std::is_class_v<T> ||
std::is_union_v<T>)&&!std::is_trivially_default_constructible_v<T>;
static_assert(IsPointer || IsNonTriviallyDefaultConstructibleClassOrUnion,
"T() must evaluate to a safely-initialized T");
#endif
return T();
}
#ifdef JS_DEBUG
/**
* For generational GC, assert that an object is in the tenured generation as
* opposed to being in the nursery.
*/
extern JS_FRIEND_API void AssertGCThingMustBeTenured(JSObject* obj);
extern JS_FRIEND_API void AssertGCThingIsNotNurseryAllocable(
js::gc::Cell* cell);
#else
inline void AssertGCThingMustBeTenured(JSObject* obj) {}
inline void AssertGCThingIsNotNurseryAllocable(js::gc::Cell* cell) {}
#endif
/**
* The Heap<T> class is a heap-stored reference to a JS GC thing for use outside
* the JS engine. All members of heap classes that refer to GC things should use
* Heap<T> (or possibly TenuredHeap<T>, described below).
*
* Heap<T> is an abstraction that hides some of the complexity required to
* maintain GC invariants for the contained reference. It uses operator
* overloading to provide a normal pointer interface, but adds barriers to
* notify the GC of changes.
*
* Heap<T> implements the following barriers:
*
* - Post-write barrier (necessary for generational GC).
* - Read barrier (necessary for incremental GC and cycle collector
* integration).
*
* Note Heap<T> does not have a pre-write barrier as used internally in the
* engine. The read barrier is used to mark anything read from a Heap<T> during
* an incremental GC.
*
* Heap<T> may be moved or destroyed outside of GC finalization and hence may be
* used in dynamic storage such as a Vector.
*
* Heap<T> instances must be traced when their containing object is traced to
* keep the pointed-to GC thing alive.
*
* Heap<T> objects should only be used on the heap. GC references stored on the
* C/C++ stack must use Rooted/Handle/MutableHandle instead.
*
* Type T must be a public GC pointer type.
*/
template <typename T>
class MOZ_NON_MEMMOVABLE Heap : public js::HeapBase<T, Heap<T>> {
// Please note: this can actually also be used by nsXBLMaybeCompiled<T>, for
// legacy reasons.
static_assert(js::IsHeapConstructibleType<T>::value,
"Type T must be a public GC pointer type");
public:
using ElementType = T;
Heap() : ptr(SafelyInitialized<T>()) {
// No barriers are required for initialization to the default value.
static_assert(sizeof(T) == sizeof(Heap<T>),
"Heap<T> must be binary compatible with T.");
}
explicit Heap(const T& p) { init(p); }
/*
* For Heap, move semantics are equivalent to copy semantics. However, we want
* the copy constructor to be explicit, and an explicit move constructor
* breaks common usage of move semantics, so we need to define both, even
* though they are equivalent.
*/
explicit Heap(const Heap<T>& other) { init(other.ptr); }
Heap(Heap<T>&& other) { init(other.ptr); }
Heap& operator=(Heap<T>&& other) {
set(other.unbarrieredGet());
other.set(SafelyInitialized<T>());
return *this;
}
~Heap() { postWriteBarrier(ptr, SafelyInitialized<T>()); }
DECLARE_POINTER_CONSTREF_OPS(T);
DECLARE_POINTER_ASSIGN_OPS(Heap, T);
const T* address() const { return &ptr; }
void exposeToActiveJS() const { js::BarrierMethods<T>::exposeToJS(ptr); }
const T& get() const {
exposeToActiveJS();
return ptr;
}
const T& unbarrieredGet() const { return ptr; }
void set(const T& newPtr) {
T tmp = ptr;
ptr = newPtr;
postWriteBarrier(tmp, ptr);
}
T* unsafeGet() { return &ptr; }
void unbarrieredSet(const T& newPtr) { ptr = newPtr; }
explicit operator bool() const {
return bool(js::BarrierMethods<T>::asGCThingOrNull(ptr));
}
explicit operator bool() {
return bool(js::BarrierMethods<T>::asGCThingOrNull(ptr));
}
private:
void init(const T& newPtr) {
ptr = newPtr;
postWriteBarrier(SafelyInitialized<T>(), ptr);
}
void postWriteBarrier(const T& prev, const T& next) {
js::BarrierMethods<T>::postWriteBarrier(&ptr, prev, next);
}
T ptr;
};
namespace detail {
template <typename T>
struct DefineComparisonOps<Heap<T>> : std::true_type {
static const T& get(const Heap<T>& v) { return v.unbarrieredGet(); }
};
} // namespace detail
static MOZ_ALWAYS_INLINE bool ObjectIsTenured(JSObject* obj) {
return !js::gc::IsInsideNursery(reinterpret_cast<js::gc::Cell*>(obj));
}
static MOZ_ALWAYS_INLINE bool ObjectIsTenured(const Heap<JSObject*>& obj) {
return ObjectIsTenured(obj.unbarrieredGet());
}
static MOZ_ALWAYS_INLINE bool ObjectIsMarkedGray(JSObject* obj) {
auto cell = reinterpret_cast<js::gc::Cell*>(obj);
return js::gc::detail::CellIsMarkedGrayIfKnown(cell);
}
static MOZ_ALWAYS_INLINE bool ObjectIsMarkedGray(
const JS::Heap<JSObject*>& obj) {
return ObjectIsMarkedGray(obj.unbarrieredGet());
}
// The following *IsNotGray functions take account of the eventual
// gray marking state at the end of any ongoing incremental GC by
// delaying the checks if necessary.
#ifdef DEBUG
inline void AssertCellIsNotGray(const js::gc::Cell* maybeCell) {
if (maybeCell) {
js::gc::detail::AssertCellIsNotGray(maybeCell);
}
}
inline void AssertObjectIsNotGray(JSObject* maybeObj) {
AssertCellIsNotGray(reinterpret_cast<js::gc::Cell*>(maybeObj));
}
inline void AssertObjectIsNotGray(const JS::Heap<JSObject*>& obj) {
AssertObjectIsNotGray(obj.unbarrieredGet());
}
#else
inline void AssertCellIsNotGray(js::gc::Cell* maybeCell) {}
inline void AssertObjectIsNotGray(JSObject* maybeObj) {}
inline void AssertObjectIsNotGray(const JS::Heap<JSObject*>& obj) {}
#endif
/**
* The TenuredHeap<T> class is similar to the Heap<T> class above in that it
* encapsulates the GC concerns of an on-heap reference to a JS object. However,
* it has two important differences:
*
* 1) Pointers which are statically known to only reference "tenured" objects
* can avoid the extra overhead of SpiderMonkey's write barriers.
*
* 2) Objects in the "tenured" heap have stronger alignment restrictions than
* those in the "nursery", so it is possible to store flags in the lower
* bits of pointers known to be tenured. TenuredHeap wraps a normal tagged
* pointer with a nice API for accessing the flag bits and adds various
* assertions to ensure that it is not mis-used.
*
* GC things are said to be "tenured" when they are located in the long-lived
* heap: e.g. they have gained tenure as an object by surviving past at least
* one GC. For performance, SpiderMonkey allocates some things which are known
* to normally be long lived directly into the tenured generation; for example,
* global objects. Additionally, SpiderMonkey does not visit individual objects
* when deleting non-tenured objects, so object with finalizers are also always
* tenured; for instance, this includes most DOM objects.
*
* The considerations to keep in mind when using a TenuredHeap<T> vs a normal
* Heap<T> are:
*
* - It is invalid for a TenuredHeap<T> to refer to a non-tenured thing.
* - It is however valid for a Heap<T> to refer to a tenured thing.
* - It is not possible to store flag bits in a Heap<T>.
*/
template <typename T>
class TenuredHeap : public js::HeapBase<T, TenuredHeap<T>> {
public:
using ElementType = T;
TenuredHeap() : bits(0) {
static_assert(sizeof(T) == sizeof(TenuredHeap<T>),
"TenuredHeap<T> must be binary compatible with T.");
}
explicit TenuredHeap(T p) : bits(0) { setPtr(p); }
explicit TenuredHeap(const TenuredHeap<T>& p) : bits(0) {
setPtr(p.getPtr());
}
void setPtr(T newPtr) {
MOZ_ASSERT((reinterpret_cast<uintptr_t>(newPtr) & flagsMask) == 0);
MOZ_ASSERT(js::gc::IsCellPointerValidOrNull(newPtr));
if (newPtr) {
AssertGCThingMustBeTenured(newPtr);
}
bits = (bits & flagsMask) | reinterpret_cast<uintptr_t>(newPtr);
}
void setFlags(uintptr_t flagsToSet) {
MOZ_ASSERT((flagsToSet & ~flagsMask) == 0);
bits |= flagsToSet;
}
void unsetFlags(uintptr_t flagsToUnset) {
MOZ_ASSERT((flagsToUnset & ~flagsMask) == 0);
bits &= ~flagsToUnset;
}
bool hasFlag(uintptr_t flag) const {
MOZ_ASSERT((flag & ~flagsMask) == 0);
return (bits & flag) != 0;
}
T unbarrieredGetPtr() const { return reinterpret_cast<T>(bits & ~flagsMask); }
uintptr_t getFlags() const { return bits & flagsMask; }
void exposeToActiveJS() const {
js::BarrierMethods<T>::exposeToJS(unbarrieredGetPtr());
}
T getPtr() const {
exposeToActiveJS();
return unbarrieredGetPtr();
}
operator T() const { return getPtr(); }
T operator->() const { return getPtr(); }
explicit operator bool() const {
return bool(js::BarrierMethods<T>::asGCThingOrNull(unbarrieredGetPtr()));
}
explicit operator bool() {
return bool(js::BarrierMethods<T>::asGCThingOrNull(unbarrieredGetPtr()));
}
TenuredHeap<T>& operator=(T p) {
setPtr(p);
return *this;
}
TenuredHeap<T>& operator=(const TenuredHeap<T>& other) {
bits = other.bits;
return *this;
}
private:
enum {
maskBits = 3,
flagsMask = (1 << maskBits) - 1,
};
uintptr_t bits;
};
namespace detail {
template <typename T>
struct DefineComparisonOps<TenuredHeap<T>> : std::true_type {
static const T get(const TenuredHeap<T>& v) { return v.unbarrieredGetPtr(); }
};
} // namespace detail
// std::swap uses a stack temporary, which prevents classes like Heap<T>
// from being declared MOZ_HEAP_CLASS.
template <typename T>
void swap(TenuredHeap<T>& aX, TenuredHeap<T>& aY) {
T tmp = aX;
aX = aY;
aY = tmp;
}
template <typename T>
void swap(Heap<T>& aX, Heap<T>& aY) {
T tmp = aX;
aX = aY;
aY = tmp;
}
static MOZ_ALWAYS_INLINE bool ObjectIsMarkedGray(
const JS::TenuredHeap<JSObject*>& obj) {
return ObjectIsMarkedGray(obj.unbarrieredGetPtr());
}
template <typename T>
class MutableHandle;
template <typename T>
class Rooted;
template <typename T>
class PersistentRooted;
/**
* Reference to a T that has been rooted elsewhere. This is most useful
* as a parameter type, which guarantees that the T lvalue is properly
* rooted. See "Move GC Stack Rooting" above.
*
* If you want to add additional methods to Handle for a specific
* specialization, define a HandleBase<T> specialization containing them.
*/
template <typename T>
class MOZ_NONHEAP_CLASS Handle : public js::HandleBase<T, Handle<T>> {
friend class MutableHandle<T>;
public:
using ElementType = T;
Handle(const Handle<T>&) = default;
/* Creates a handle from a handle of a type convertible to T. */
template <typename S>
MOZ_IMPLICIT Handle(
Handle<S> handle,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy = 0) {
static_assert(sizeof(Handle<T>) == sizeof(T*),
"Handle must be binary compatible with T*.");
ptr = reinterpret_cast<const T*>(handle.address());
}
MOZ_IMPLICIT Handle(decltype(nullptr)) {
static_assert(std::is_pointer_v<T>,
"nullptr_t overload not valid for non-pointer types");
static void* const ConstNullValue = nullptr;
ptr = reinterpret_cast<const T*>(&ConstNullValue);
}
MOZ_IMPLICIT Handle(MutableHandle<T> handle) { ptr = handle.address(); }
/*
* Take care when calling this method!
*
* This creates a Handle from the raw location of a T.
*
* It should be called only if the following conditions hold:
*
* 1) the location of the T is guaranteed to be marked (for some reason
* other than being a Rooted), e.g., if it is guaranteed to be reachable
* from an implicit root.
*
* 2) the contents of the location are immutable, or at least cannot change
* for the lifetime of the handle, as its users may not expect its value
* to change underneath them.
*/
static constexpr Handle fromMarkedLocation(const T* p) {
return Handle(p, DeliberatelyChoosingThisOverload,
ImUsingThisOnlyInFromFromMarkedLocation);
}
/*
* Construct a handle from an explicitly rooted location. This is the
* normal way to create a handle, and normally happens implicitly.
*/
template <typename S>
inline MOZ_IMPLICIT Handle(
const Rooted<S>& root,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy = 0);
template <typename S>
inline MOZ_IMPLICIT Handle(
const PersistentRooted<S>& root,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy = 0);
/* Construct a read only handle from a mutable handle. */
template <typename S>
inline MOZ_IMPLICIT Handle(
MutableHandle<S>& root,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy = 0);
DECLARE_POINTER_CONSTREF_OPS(T);
DECLARE_NONPOINTER_ACCESSOR_METHODS(*ptr);
private:
Handle() = default;
DELETE_ASSIGNMENT_OPS(Handle, T);
enum Disambiguator { DeliberatelyChoosingThisOverload = 42 };
enum CallerIdentity { ImUsingThisOnlyInFromFromMarkedLocation = 17 };
constexpr Handle(const T* p, Disambiguator, CallerIdentity) : ptr(p) {}
const T* ptr;
};
namespace detail {
template <typename T>
struct DefineComparisonOps<Handle<T>> : std::true_type {
static const T& get(const Handle<T>& v) { return v.get(); }
};
} // namespace detail
/**
* Similar to a handle, but the underlying storage can be changed. This is
* useful for outparams.
*
* If you want to add additional methods to MutableHandle for a specific
* specialization, define a MutableHandleBase<T> specialization containing
* them.
*/
template <typename T>
class MOZ_STACK_CLASS MutableHandle
: public js::MutableHandleBase<T, MutableHandle<T>> {
public:
using ElementType = T;
inline MOZ_IMPLICIT MutableHandle(Rooted<T>* root);
inline MOZ_IMPLICIT MutableHandle(PersistentRooted<T>* root);
private:
// Disallow nullptr for overloading purposes.
MutableHandle(decltype(nullptr)) = delete;
public:
MutableHandle(const MutableHandle<T>&) = default;
void set(const T& v) {
*ptr = v;
MOZ_ASSERT(GCPolicy<T>::isValid(*ptr));
}
void set(T&& v) {
*ptr = std::move(v);
MOZ_ASSERT(GCPolicy<T>::isValid(*ptr));
}
/*
* This may be called only if the location of the T is guaranteed
* to be marked (for some reason other than being a Rooted),
* e.g., if it is guaranteed to be reachable from an implicit root.
*
* Create a MutableHandle from a raw location of a T.
*/
static MutableHandle fromMarkedLocation(T* p) {
MutableHandle h;
h.ptr = p;
return h;
}
DECLARE_POINTER_CONSTREF_OPS(T);
DECLARE_NONPOINTER_ACCESSOR_METHODS(*ptr);
DECLARE_NONPOINTER_MUTABLE_ACCESSOR_METHODS(*ptr);
private:
MutableHandle() = default;
DELETE_ASSIGNMENT_OPS(MutableHandle, T);
T* ptr;
};
namespace detail {
template <typename T>
struct DefineComparisonOps<MutableHandle<T>> : std::true_type {
static const T& get(const MutableHandle<T>& v) { return v.get(); }
};
} // namespace detail
} /* namespace JS */
namespace js {
namespace detail {
// Default implementations for barrier methods on GC thing pointers.
template <typename T>
struct PtrBarrierMethodsBase {
static T* initial() { return nullptr; }
static gc::Cell* asGCThingOrNull(T* v) {
if (!v) {
return nullptr;
}
MOZ_ASSERT(uintptr_t(v) > 32);
return reinterpret_cast<gc::Cell*>(v);
}
static void exposeToJS(T* t) {
if (t) {
js::gc::ExposeGCThingToActiveJS(JS::GCCellPtr(t));
}
}
};
} // namespace detail
template <typename T>
struct BarrierMethods<T*> : public detail::PtrBarrierMethodsBase<T> {
static void postWriteBarrier(T** vp, T* prev, T* next) {
if (next) {
JS::AssertGCThingIsNotNurseryAllocable(
reinterpret_cast<js::gc::Cell*>(next));
}
}
};
template <>
struct BarrierMethods<JSObject*>
: public detail::PtrBarrierMethodsBase<JSObject> {
static void postWriteBarrier(JSObject** vp, JSObject* prev, JSObject* next) {
JS::HeapObjectPostWriteBarrier(vp, prev, next);
}
static void exposeToJS(JSObject* obj) {
if (obj) {
JS::ExposeObjectToActiveJS(obj);
}
}
};
template <>
struct BarrierMethods<JSFunction*>
: public detail::PtrBarrierMethodsBase<JSFunction> {
static void postWriteBarrier(JSFunction** vp, JSFunction* prev,
JSFunction* next) {
JS::HeapObjectPostWriteBarrier(reinterpret_cast<JSObject**>(vp),
reinterpret_cast<JSObject*>(prev),
reinterpret_cast<JSObject*>(next));
}
static void exposeToJS(JSFunction* fun) {
if (fun) {
JS::ExposeObjectToActiveJS(reinterpret_cast<JSObject*>(fun));
}
}
};
template <>
struct BarrierMethods<JSString*>
: public detail::PtrBarrierMethodsBase<JSString> {
static void postWriteBarrier(JSString** vp, JSString* prev, JSString* next) {
JS::HeapStringPostWriteBarrier(vp, prev, next);
}
};
template <>
struct BarrierMethods<JS::BigInt*>
: public detail::PtrBarrierMethodsBase<JS::BigInt> {
static void postWriteBarrier(JS::BigInt** vp, JS::BigInt* prev,
JS::BigInt* next) {
JS::HeapBigIntPostWriteBarrier(vp, prev, next);
}
};
// Provide hash codes for Cell kinds that may be relocated and, thus, not have
// a stable address to use as the base for a hash code. Instead of the address,
// this hasher uses Cell::getUniqueId to provide exact matches and as a base
// for generating hash codes.
//
// Note: this hasher, like PointerHasher can "hash" a nullptr. While a nullptr
// would not likely be a useful key, there are some cases where being able to
// hash a nullptr is useful, either on purpose or because of bugs:
// (1) existence checks where the key may happen to be null and (2) some
// aggregate Lookup kinds embed a JSObject* that is frequently null and do not
// null test before dispatching to the hasher.
template <typename T>
struct JS_PUBLIC_API MovableCellHasher {
using Key = T;
using Lookup = T;
static bool hasHash(const Lookup& l);
static bool ensureHash(const Lookup& l);
static HashNumber hash(const Lookup& l);
static bool match(const Key& k, const Lookup& l);
// The rekey hash policy method is not provided since you dont't need to
// rekey any more when using this policy.
};
template <typename T>
struct JS_PUBLIC_API MovableCellHasher<JS::Heap<T>> {
using Key = JS::Heap<T>;
using Lookup = T;
static bool hasHash(const Lookup& l) {
return MovableCellHasher<T>::hasHash(l);
}
static bool ensureHash(const Lookup& l) {
return MovableCellHasher<T>::ensureHash(l);
}
static HashNumber hash(const Lookup& l) {
return MovableCellHasher<T>::hash(l);
}
static bool match(const Key& k, const Lookup& l) {
return MovableCellHasher<T>::match(k.unbarrieredGet(), l);
}
};
} // namespace js
namespace mozilla {
template <typename T>
struct FallibleHashMethods<js::MovableCellHasher<T>> {
template <typename Lookup>
static bool hasHash(Lookup&& l) {
return js::MovableCellHasher<T>::hasHash(std::forward<Lookup>(l));
}
template <typename Lookup>
static bool ensureHash(Lookup&& l) {
return js::MovableCellHasher<T>::ensureHash(std::forward<Lookup>(l));
}
};
} // namespace mozilla
namespace js {
struct VirtualTraceable {
virtual ~VirtualTraceable() = default;
virtual void trace(JSTracer* trc, const char* name) = 0;
};
template <typename T>
struct RootedTraceable final : public VirtualTraceable {
static_assert(JS::MapTypeToRootKind<T>::kind == JS::RootKind::Traceable,
"RootedTraceable is intended only for usage with a Traceable");
T ptr;
template <typename U>
MOZ_IMPLICIT RootedTraceable(U&& initial) : ptr(std::forward<U>(initial)) {}
operator T&() { return ptr; }
operator const T&() const { return ptr; }
void trace(JSTracer* trc, const char* name) override {
JS::GCPolicy<T>::trace(trc, &ptr, name);
}
};
template <typename T>
struct RootedTraceableTraits {
static T* address(RootedTraceable<T>& self) { return &self.ptr; }
static const T* address(const RootedTraceable<T>& self) { return &self.ptr; }
static void trace(JSTracer* trc, VirtualTraceable* thingp, const char* name);
};
template <typename T>
struct RootedGCThingTraits {
static T* address(T& self) { return &self; }
static const T* address(const T& self) { return &self; }
static void trace(JSTracer* trc, T* thingp, const char* name);
};
} /* namespace js */
namespace JS {
class JS_PUBLIC_API AutoGCRooter;
enum class AutoGCRooterKind : uint8_t {
WrapperVector, /* js::AutoWrapperVector */
Wrapper, /* js::AutoWrapperRooter */
Custom, /* js::CustomAutoRooter */
Limit
};
namespace detail {
// Dummy type to store root list entry pointers as. This code does not just use
// the actual type, because then eg JSObject* and JSFunction* would be assumed
// to never alias but they do (they are stored in the same list). Also, do not
// use `void*` so that `Rooted<void*>` is a compile error.
struct RootListEntry;
} // namespace detail
template <>
struct MapTypeToRootKind<detail::RootListEntry*> {
static const RootKind kind = RootKind::Traceable;
};
using RootedListHeads =
mozilla::EnumeratedArray<RootKind, RootKind::Limit,
Rooted<detail::RootListEntry*>*>;
using AutoRooterListHeads =
mozilla::EnumeratedArray<AutoGCRooterKind, AutoGCRooterKind::Limit,
AutoGCRooter*>;
// Superclass of JSContext which can be used for rooting data in use by the
// current thread but that does not provide all the functions of a JSContext.
class RootingContext {
// Stack GC roots for Rooted GC heap pointers.
RootedListHeads stackRoots_;
template <typename T>
friend class Rooted;
// Stack GC roots for AutoFooRooter classes.
AutoRooterListHeads autoGCRooters_;
friend class AutoGCRooter;
// Gecko profiling metadata.
// This isn't really rooting related. It's only here because we want
// GetContextProfilingStackIfEnabled to be inlineable into non-JS code, and
// we didn't want to add another superclass of JSContext just for this.
js::GeckoProfilerThread geckoProfiler_;
public:
RootingContext();
void traceStackRoots(JSTracer* trc);
/* Implemented in gc/RootMarking.cpp. */
void traceAllGCRooters(JSTracer* trc);
void traceWrapperGCRooters(JSTracer* trc);
static void traceGCRooterList(JSTracer* trc, AutoGCRooter* head);
void checkNoGCRooters();
js::GeckoProfilerThread& geckoProfiler() { return geckoProfiler_; }
protected:
// The remaining members in this class should only be accessed through
// JSContext pointers. They are unrelated to rooting and are in place so
// that inlined API functions can directly access the data.
/* The current realm. */
Realm* realm_;
/* The current zone. */
Zone* zone_;
public:
/* Limit pointer for checking native stack consumption. */
uintptr_t nativeStackLimit[StackKindCount];
#ifdef __wasi__
// For WASI we can't catch call-stack overflows with stack-pointer checks, so
// we count recursion depth with RAII based AutoCheckRecursionLimit.
uint32_t wasiRecursionDepth = 0u;
static constexpr uint32_t wasiRecursionDepthLimit = 100u;
#endif // __wasi__
static const RootingContext* get(const JSContext* cx) {
return reinterpret_cast<const RootingContext*>(cx);
}
static RootingContext* get(JSContext* cx) {
return reinterpret_cast<RootingContext*>(cx);
}
friend JS::Realm* js::GetContextRealm(const JSContext* cx);
friend JS::Zone* js::GetContextZone(const JSContext* cx);
};
class JS_PUBLIC_API AutoGCRooter {
public:
using Kind = AutoGCRooterKind;
AutoGCRooter(JSContext* cx, Kind kind)
: AutoGCRooter(JS::RootingContext::get(cx), kind) {}
AutoGCRooter(RootingContext* cx, Kind kind)
: down(cx->autoGCRooters_[kind]),
stackTop(&cx->autoGCRooters_[kind]),
kind_(kind) {
MOZ_ASSERT(this != *stackTop);
*stackTop = this;
}
~AutoGCRooter() {
MOZ_ASSERT(this == *stackTop);
*stackTop = down;
}
void trace(JSTracer* trc);
private:
friend class RootingContext;
AutoGCRooter* const down;
AutoGCRooter** const stackTop;
/*
* Discriminates actual subclass of this being used. The meaning is
* indicated by the corresponding value in the Kind enum.
*/
Kind kind_;
/* No copy or assignment semantics. */
AutoGCRooter(AutoGCRooter& ida) = delete;
void operator=(AutoGCRooter& ida) = delete;
} JS_HAZ_ROOTED_BASE;
/**
* Custom rooting behavior for internal and external clients.
*
* Deprecated. Where possible, use Rooted<> instead.
*/
class MOZ_RAII JS_PUBLIC_API CustomAutoRooter : private AutoGCRooter {
public:
template <typename CX>
explicit CustomAutoRooter(const CX& cx)
: AutoGCRooter(cx, AutoGCRooter::Kind::Custom) {}
friend void AutoGCRooter::trace(JSTracer* trc);
protected:
virtual ~CustomAutoRooter() = default;
/** Supplied by derived class to trace roots. */
virtual void trace(JSTracer* trc) = 0;
};
namespace detail {
template <typename T>
using RootedPtr =
std::conditional_t<MapTypeToRootKind<T>::kind == JS::RootKind::Traceable,
js::RootedTraceable<T>, T>;
template <typename T>
using RootedPtrTraits =
std::conditional_t<MapTypeToRootKind<T>::kind == JS::RootKind::Traceable,
js::RootedTraceableTraits<T>,
js::RootedGCThingTraits<T>>;
// Dummy types to make it easier to understand template overload preference
// ordering.
struct FallbackOverload {};
struct PreferredOverload : FallbackOverload {};
using OverloadSelector = PreferredOverload;
} /* namespace detail */
/**
* Local variable of type T whose value is always rooted. This is typically
* used for local variables, or for non-rooted values being passed to a
* function that requires a handle, e.g. Foo(Root<T>(cx, x)).
*
* If you want to add additional methods to Rooted for a specific
* specialization, define a RootedBase<T> specialization containing them.
*/
template <typename T>
class MOZ_RAII Rooted : public js::RootedBase<T, Rooted<T>> {
using Ptr = detail::RootedPtr<T>;
using PtrTraits = detail::RootedPtrTraits<T>;
inline void registerWithRootLists(RootedListHeads& roots) {
this->stack = &roots[JS::MapTypeToRootKind<T>::kind];
this->prev = *stack;
*stack = reinterpret_cast<Rooted<detail::RootListEntry*>*>(this);
}
inline RootedListHeads& rootLists(RootingContext* cx) {
return cx->stackRoots_;
}
inline RootedListHeads& rootLists(JSContext* cx) {
return rootLists(RootingContext::get(cx));
}
// Define either one or two Rooted(cx) constructors: the fallback one, which
// constructs a Rooted holding a SafelyInitialized<T>, and a convenience one
// for types that can be constructed with a cx, which will give a Rooted
// holding a T(cx).
// Dummy type to distinguish these constructors from Rooted(cx, initial)
struct CtorDispatcher {};
// Normal case: construct an empty Rooted holding a safely initialized but
// empty T.
template <typename RootingContext>
Rooted(const RootingContext& cx, CtorDispatcher, detail::FallbackOverload)
: Rooted(cx, SafelyInitialized<T>()) {}
// If T can be constructed with a cx, then define another constructor for it
// that will be preferred.
template <
typename RootingContext,
typename = std::enable_if_t<std::is_constructible_v<T, RootingContext>>>
Rooted(const RootingContext& cx, CtorDispatcher, detail::PreferredOverload)
: Rooted(cx, T(cx)) {}
public:
using ElementType = T;
// Construct an empty Rooted. Delegates to an internal constructor that
// chooses a specific meaning of "empty" depending on whether T can be
// constructed with a cx.
template <typename RootingContext>
explicit Rooted(const RootingContext& cx)
: Rooted(cx, CtorDispatcher(), detail::OverloadSelector()) {}
template <typename RootingContext, typename S>
Rooted(const RootingContext& cx, S&& initial)
: ptr(std::forward<S>(initial)) {
MOZ_ASSERT(GCPolicy<T>::isValid(ptr));
registerWithRootLists(rootLists(cx));
}
~Rooted() {
MOZ_ASSERT(*stack ==
reinterpret_cast<Rooted<detail::RootListEntry*>*>(this));
*stack = prev;
}
Rooted<T>* previous() { return reinterpret_cast<Rooted<T>*>(prev); }
/*
* This method is public for Rooted so that Codegen.py can use a Rooted
* interchangeably with a MutableHandleValue.
*/
void set(const T& value) {
ptr = value;
MOZ_ASSERT(GCPolicy<T>::isValid(ptr));
}
void set(T&& value) {
ptr = std::move(value);
MOZ_ASSERT(GCPolicy<T>::isValid(ptr));
}
DECLARE_POINTER_CONSTREF_OPS(T);
DECLARE_POINTER_ASSIGN_OPS(Rooted, T);
T& get() { return ptr; }
const T& get() const { return ptr; }
T* address() { return PtrTraits::address(ptr); }
const T* address() const { return PtrTraits::address(ptr); }
void trace(JSTracer* trc, const char* name);
private:
/*
* These need to be templated on RootListEntry* to avoid aliasing issues
* between, for example, Rooted<JSObject*> and Rooted<JSFunction*>, which use
* the same stack head pointer for different classes.
*/
Rooted<detail::RootListEntry*>** stack;
Rooted<detail::RootListEntry*>* prev;
Ptr ptr;
Rooted(const Rooted&) = delete;
} JS_HAZ_ROOTED;
namespace detail {
template <typename T>
struct DefineComparisonOps<Rooted<T>> : std::true_type {
static const T& get(const Rooted<T>& v) { return v.get(); }
};
} // namespace detail
} /* namespace JS */
namespace js {
/*
* Inlinable accessors for JSContext.
*
* - These must not be available on the more restricted superclasses of
* JSContext, so we can't simply define them on RootingContext.
*
* - They're perfectly ordinary JSContext functionality, so ought to be
* usable without resorting to jsfriendapi.h, and when JSContext is an
* incomplete type.
*/
inline JS::Realm* GetContextRealm(const JSContext* cx) {
return JS::RootingContext::get(cx)->realm_;
}
inline JS::Compartment* GetContextCompartment(const JSContext* cx) {
if (JS::Realm* realm = GetContextRealm(cx)) {
return GetCompartmentForRealm(realm);
}
return nullptr;
}
inline JS::Zone* GetContextZone(const JSContext* cx) {
return JS::RootingContext::get(cx)->zone_;
}
inline ProfilingStack* GetContextProfilingStackIfEnabled(JSContext* cx) {
return JS::RootingContext::get(cx)
->geckoProfiler()
.getProfilingStackIfEnabled();
}
/**
* Augment the generic Rooted<T> interface when T = JSObject* with
* class-querying and downcasting operations.
*
* Given a Rooted<JSObject*> obj, one can view
* Handle<StringObject*> h = obj.as<StringObject*>();
* as an optimization of
* Rooted<StringObject*> rooted(cx, &obj->as<StringObject*>());
* Handle<StringObject*> h = rooted;
*/
template <typename Container>
class RootedBase<JSObject*, Container>
: public MutableWrappedPtrOperations<JSObject*, Container> {
public:
template <class U>
JS::Handle<U*> as() const;
};
/**
* Augment the generic Handle<T> interface when T = JSObject* with
* downcasting operations.
*
* Given a Handle<JSObject*> obj, one can view
* Handle<StringObject*> h = obj.as<StringObject*>();
* as an optimization of
* Rooted<StringObject*> rooted(cx, &obj->as<StringObject*>());
* Handle<StringObject*> h = rooted;
*/
template <typename Container>
class HandleBase<JSObject*, Container>
: public WrappedPtrOperations<JSObject*, Container> {
public:
template <class U>
JS::Handle<U*> as() const;
};
} /* namespace js */
namespace JS {
template <typename T>
template <typename S>
inline Handle<T>::Handle(
const Rooted<S>& root,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy) {
ptr = reinterpret_cast<const T*>(root.address());
}
template <typename T>
template <typename S>
inline Handle<T>::Handle(
const PersistentRooted<S>& root,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy) {
ptr = reinterpret_cast<const T*>(root.address());
}
template <typename T>
template <typename S>
inline Handle<T>::Handle(
MutableHandle<S>& root,
std::enable_if_t<std::is_convertible_v<S, T>, int> dummy) {
ptr = reinterpret_cast<const T*>(root.address());
}
template <typename T>
inline MutableHandle<T>::MutableHandle(Rooted<T>* root) {
static_assert(sizeof(MutableHandle<T>) == sizeof(T*),
"MutableHandle must be binary compatible with T*.");
ptr = root->address();
}
template <typename T>
inline MutableHandle<T>::MutableHandle(PersistentRooted<T>* root) {
static_assert(sizeof(MutableHandle<T>) == sizeof(T*),
"MutableHandle must be binary compatible with T*.");
ptr = root->address();
}
JS_PUBLIC_API void AddPersistentRoot(
RootingContext* cx, RootKind kind,
PersistentRooted<detail::RootListEntry*>* root);
JS_PUBLIC_API void AddPersistentRoot(
JSRuntime* rt, RootKind kind,
PersistentRooted<detail::RootListEntry*>* root);
/**
* A copyable, assignable global GC root type with arbitrary lifetime, an
* infallible constructor, and automatic unrooting on destruction.
*
* These roots can be used in heap-allocated data structures, so they are not
* associated with any particular JSContext or stack. They are registered with
* the JSRuntime itself, without locking. Initialization may take place on
* construction, or in two phases if the no-argument constructor is called
* followed by init().
*
* Note that you must not use an PersistentRooted in an object owned by a JS
* object:
*
* Whenever one object whose lifetime is decided by the GC refers to another
* such object, that edge must be traced only if the owning JS object is traced.
* This applies not only to JS objects (which obviously are managed by the GC)
* but also to C++ objects owned by JS objects.
*
* If you put a PersistentRooted in such a C++ object, that is almost certainly
* a leak. When a GC begins, the referent of the PersistentRooted is treated as
* live, unconditionally (because a PersistentRooted is a *root*), even if the
* JS object that owns it is unreachable. If there is any path from that
* referent back to the JS object, then the C++ object containing the
* PersistentRooted will not be destructed, and the whole blob of objects will
* not be freed, even if there are no references to them from the outside.
*
* In the context of Firefox, this is a severe restriction: almost everything in
* Firefox is owned by some JS object or another, so using PersistentRooted in
* such objects would introduce leaks. For these kinds of edges, Heap<T> or
* TenuredHeap<T> would be better types. It's up to the implementor of the type
* containing Heap<T> or TenuredHeap<T> members to make sure their referents get
* marked when the object itself is marked.
*/
template <typename T>
class PersistentRooted
: public js::RootedBase<T, PersistentRooted<T>>,
private mozilla::LinkedListElement<PersistentRooted<T>> {
using ListBase = mozilla::LinkedListElement<PersistentRooted<T>>;
using Ptr = detail::RootedPtr<T>;
using PtrTraits = detail::RootedPtrTraits<T>;
friend class mozilla::LinkedList<PersistentRooted>;
friend class mozilla::LinkedListElement<PersistentRooted>;
void registerWithRootLists(RootingContext* cx) {
MOZ_ASSERT(!initialized());
JS::RootKind kind = JS::MapTypeToRootKind<T>::kind;
AddPersistentRoot(
cx, kind,
reinterpret_cast<JS::PersistentRooted<detail::RootListEntry*>*>(this));
}
void registerWithRootLists(JSRuntime* rt) {
MOZ_ASSERT(!initialized());
JS::RootKind kind = JS::MapTypeToRootKind<T>::kind;
AddPersistentRoot(
rt, kind,
reinterpret_cast<JS::PersistentRooted<detail::RootListEntry*>*>(this));
}
public:
using ElementType = T;
PersistentRooted() : ptr(SafelyInitialized<T>()) {}
explicit PersistentRooted(RootingContext* cx) : ptr(SafelyInitialized<T>()) {
registerWithRootLists(cx);
}
explicit PersistentRooted(JSContext* cx) : ptr(SafelyInitialized<T>()) {
registerWithRootLists(RootingContext::get(cx));
}
template <typename U>
PersistentRooted(RootingContext* cx, U&& initial)
: ptr(std::forward<U>(initial)) {
registerWithRootLists(cx);
}
template <typename U>
PersistentRooted(JSContext* cx, U&& initial) : ptr(std::forward<U>(initial)) {
registerWithRootLists(RootingContext::get(cx));
}
explicit PersistentRooted(JSRuntime* rt) : ptr(SafelyInitialized<T>()) {
registerWithRootLists(rt);
}
template <typename U>
PersistentRooted(JSRuntime* rt, U&& initial) : ptr(std::forward<U>(initial)) {
registerWithRootLists(rt);
}
PersistentRooted(const PersistentRooted& rhs)
: mozilla::LinkedListElement<PersistentRooted<T>>(), ptr(rhs.ptr) {
/*
* Copy construction takes advantage of the fact that the original
* is already inserted, and simply adds itself to whatever list the
* original was on - no JSRuntime pointer needed.
*
* This requires mutating rhs's links, but those should be 'mutable'
* anyway. C++ doesn't let us declare mutable base classes.
*/
const_cast<PersistentRooted&>(rhs).setNext(this);
}
bool initialized() const { return ListBase::isInList(); }
void init(RootingContext* cx) { init(cx, SafelyInitialized<T>()); }
void init(JSContext* cx) { init(RootingContext::get(cx)); }
template <typename U>
void init(RootingContext* cx, U&& initial) {
ptr = std::forward<U>(initial);
registerWithRootLists(cx);
}
template <typename U>
void init(JSContext* cx, U&& initial) {
ptr = std::forward<U>(initial);
registerWithRootLists(RootingContext::get(cx));
}
void reset() {
if (initialized()) {
set(SafelyInitialized<T>());
ListBase::remove();
}
}
DECLARE_POINTER_CONSTREF_OPS(T);
DECLARE_POINTER_ASSIGN_OPS(PersistentRooted, T);
T& get() { return ptr; }
const T& get() const { return ptr; }
T* address() {
MOZ_ASSERT(initialized());
return PtrTraits::address(ptr);
}
const T* address() const { return PtrTraits::address(ptr); }
template <typename U>
void set(U&& value) {
MOZ_ASSERT(initialized());
ptr = std::forward<U>(value);
}
void trace(JSTracer* trc, const char* name);
private:
Ptr ptr;
} JS_HAZ_ROOTED;
namespace detail {
template <typename T>
struct DefineComparisonOps<PersistentRooted<T>> : std::true_type {
static const T& get(const PersistentRooted<T>& v) { return v.get(); }
};
} // namespace detail
} /* namespace JS */
namespace js {
template <typename T, typename D, typename Container>
class WrappedPtrOperations<UniquePtr<T, D>, Container> {
const UniquePtr<T, D>& uniquePtr() const {
return static_cast<const Container*>(this)->get();
}
public:
explicit operator bool() const { return !!uniquePtr(); }
T* get() const { return uniquePtr().get(); }
T* operator->() const { return get(); }
T& operator*() const { return *uniquePtr(); }
};
template <typename T, typename D, typename Container>
class MutableWrappedPtrOperations<UniquePtr<T, D>, Container>
: public WrappedPtrOperations<UniquePtr<T, D>, Container> {
UniquePtr<T, D>& uniquePtr() { return static_cast<Container*>(this)->get(); }
public:
[[nodiscard]] typename UniquePtr<T, D>::Pointer release() {
return uniquePtr().release();
}
void reset(T* ptr = T()) { uniquePtr().reset(ptr); }
};
template <typename T, typename Container>
class WrappedPtrOperations<mozilla::Maybe<T>, Container> {
const mozilla::Maybe<T>& maybe() const {
return static_cast<const Container*>(this)->get();
}
public:
// This only supports a subset of Maybe's interface.
bool isSome() const { return maybe().isSome(); }
bool isNothing() const { return maybe().isNothing(); }
const T value() const { return maybe().value(); }
const T* operator->() const { return maybe().ptr(); }
const T& operator*() const { return maybe().ref(); }
};
template <typename T, typename Container>
class MutableWrappedPtrOperations<mozilla::Maybe<T>, Container>
: public WrappedPtrOperations<mozilla::Maybe<T>, Container> {
mozilla::Maybe<T>& maybe() { return static_cast<Container*>(this)->get(); }
public:
// This only supports a subset of Maybe's interface.
T* operator->() { return maybe().ptr(); }
T& operator*() { return maybe().ref(); }
void reset() { return maybe().reset(); }
};
namespace gc {
template <typename T, typename TraceCallbacks>
void CallTraceCallbackOnNonHeap(T* v, const TraceCallbacks& aCallbacks,
const char* aName, void* aClosure) {
static_assert(sizeof(T) == sizeof(JS::Heap<T>),
"T and Heap<T> must be compatible.");
MOZ_ASSERT(v);
mozilla::DebugOnly<Cell*> cell = BarrierMethods<T>::asGCThingOrNull(*v);
MOZ_ASSERT(cell);
MOZ_ASSERT(!IsInsideNursery(cell));
JS::Heap<T>* asHeapT = reinterpret_cast<JS::Heap<T>*>(v);
aCallbacks.Trace(asHeapT, aName, aClosure);
}
} /* namespace gc */
} /* namespace js */
#endif /* js_RootingAPI_h */