Adding upstream version 86.0.1.upstream/86.0.1upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 748 insertions, 0 deletions

diff --git a/js/public/Proxy.h b/js/public/Proxy.h
new file mode 100644
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--- /dev/null
+++ b/js/public/Proxy.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/. */
+
+#ifndef js_Proxy_h
+#define js_Proxy_h
+
+#include "mozilla/Maybe.h"
+
+#include "jsfriendapi.h"
+
+#include "js/Array.h"  // JS::IsArrayAnswer
+#include "js/CallNonGenericMethod.h"
+#include "js/Class.h"
+#include "js/Object.h"         // JS::GetClass
+#include "js/shadow/Object.h"  // JS::shadow::Object
+
+namespace js {
+
+class RegExpShared;
+
+class JS_FRIEND_API Wrapper;
+
+/*
+ * [SMDOC] Proxy Objects
+ *
+ * A proxy is a JSObject with highly customizable behavior. ES6 specifies a
+ * single kind of proxy, but the customization mechanisms we use to implement
+ * ES6 Proxy objects are also useful wherever an object with weird behavior is
+ * wanted. Proxies are used to implement:
+ *
+ * -   the scope objects used by the Debugger's frame.eval() method
+ *     (see js::GetDebugEnvironment)
+ *
+ * -   the khuey hack, whereby a whole compartment can be blown away
+ *     even if other compartments hold references to objects in it
+ *     (see js::NukeCrossCompartmentWrappers)
+ *
+ * -   XPConnect security wrappers, which protect chrome from malicious content
+ *     (js/xpconnect/wrappers)
+ *
+ * -   DOM objects with special property behavior, like named getters
+ *     (dom/bindings/Codegen.py generates these proxies from WebIDL)
+ *
+ * ### Proxies and internal methods
+ *
+ * ES2019 specifies 13 internal methods. The runtime semantics of just about
+ * everything a script can do to an object is specified in terms of these
+ * internal methods. For example:
+ *
+ *     JS code                      ES6 internal method that gets called
+ *     ---------------------------  --------------------------------
+ *     obj.prop                     obj.[[Get]](obj, "prop")
+ *     "prop" in obj                obj.[[HasProperty]]("prop")
+ *     new obj()                    obj.[[Construct]](<empty argument List>)
+ *
+ * With regard to the implementation of these internal methods, there are three
+ * very different kinds of object in SpiderMonkey.
+ *
+ * 1.  Native objects cover most objects and contain both internal slots and
+ *     properties. JSClassOps and ObjectOps may be used to override certain
+ *     default behaviors.
+ *
+ * 2.  Proxy objects are composed of internal slots and a ProxyHandler. The
+ *     handler contains C++ methods that can implement these standard (and
+ *     non-standard) internal methods. JSClassOps and ObjectOps for the base
+ *     ProxyObject invoke the handler methods as appropriate.
+ *
+ * 3.  Objects with custom layouts like TypedObjects. These rely on JSClassOps
+ *     and ObjectOps to implement internal methods.
+ *
+ * Native objects with custom JSClassOps / ObjectOps are used when the object
+ * behaves very similar to a normal object such as the ArrayObject and it's
+ * length property. Most usages wrapping a C++ or other type should prefer
+ * using a Proxy. Using the proxy approach makes it much easier to create an
+ * ECMAScript and JIT compatible object, particularly if using an appropriate
+ * base class.
+ *
+ * Just about anything you do to a proxy will end up going through a C++
+ * virtual method call. Possibly several. There's no reason the JITs and ICs
+ * can't specialize for particular proxies, based on the handler; but currently
+ * we don't do much of this, so the virtual method overhead typically is
+ * actually incurred.
+ *
+ * ### The proxy handler hierarchy
+ *
+ * A major use case for proxies is to forward each internal method call to
+ * another object, known as its target. The target can be an arbitrary JS
+ * object. Not every proxy has the notion of a target, however.
+ *
+ * To minimize code duplication, a set of abstract proxy handler classes is
+ * provided, from which other handlers may inherit. These abstract classes are
+ * organized in the following hierarchy:
+ *
+ *     BaseProxyHandler
+ *     |
+ *     ForwardingProxyHandler    // has a target and forwards internal methods
+ *     |
+ *     Wrapper                   // can be unwrapped to reveal target
+ *     |                         // (see js::CheckedUnwrap)
+ *     |
+ *     CrossCompartmentWrapper   // target is in another compartment;
+ *                               // implements membrane between compartments
+ *
+ * Example: Some DOM objects (including all the arraylike DOM objects) are
+ * implemented as proxies. Since these objects don't need to forward operations
+ * to any underlying JS object, BaseDOMProxyHandler directly subclasses
+ * BaseProxyHandler.
+ *
+ * Gecko's security wrappers are examples of cross-compartment wrappers.
+ *
+ * ### Proxy prototype chains
+ *
+ * While most ECMAScript internal methods are handled by simply calling the
+ * handler method, the [[GetPrototypeOf]] / [[SetPrototypeOf]] behaviors may
+ * follow one of two models:
+ *
+ * 1.  A concrete prototype object (or null) is passed to object construction
+ *     and ordinary prototype read and write applies. The prototype-related
+ *     handler hooks are never called in this case. The [[Prototype]] slot is
+ *     used to store the current prototype value.
+ *
+ * 2.  TaggedProto::LazyProto is passed to NewProxyObject (or the
+ *     ProxyOptions::lazyProto flag is set). Each read or write of the
+ *     prototype will invoke the handler. This dynamic prototype behavior may
+ *     be useful for wrapper-like objects. If this mode is used the
+ *     getPrototype handler at a minimum must be implemented.
+ *
+ *     NOTE: In this mode the [[Prototype]] internal slot is unavailable and
+ *           must be simulated if needed. This is non-standard, but an
+ *           appropriate handler can hide this implementation detail.
+ *
+ * One subtlety here is that ECMAScript has a notion of "ordinary" prototypes.
+ * An object that doesn't override [[GetPrototypeOf]] is considered to have an
+ * ordinary prototype. The getPrototypeIfOrdinary handler must be implemented
+ * by you or your base class. Typically model 1 will be considered "ordinary"
+ * and model 2 will not.
+ */
+
+/*
+ * BaseProxyHandler is the most generic kind of proxy handler. It does not make
+ * any assumptions about the target. Consequently, it does not provide any
+ * default implementation for most methods. As a convenience, a few high-level
+ * methods, like get() and set(), are given default implementations that work by
+ * calling the low-level methods, like getOwnPropertyDescriptor().
+ *
+ * Important: If you add a method here, you should probably also add a
+ * Proxy::foo entry point with an AutoEnterPolicy. If you don't, you need an
+ * explicit override for the method in SecurityWrapper. See bug 945826 comment
+ * 0.
+ */
+class JS_FRIEND_API BaseProxyHandler {
+  /*
+   * Sometimes it's desirable to designate groups of proxy handlers as
+   * "similar". For this, we use the notion of a "family": A consumer-provided
+   * opaque pointer that designates the larger group to which this proxy
+   * belongs.
+   *
+   * If it will never be important to differentiate this proxy from others as
+   * part of a distinct group, nullptr may be used instead.
+   */
+  const void* mFamily;
+
+  /*
+   * Proxy handlers can use mHasPrototype to request the following special
+   * treatment from the JS engine:
+   *
+   *   - When mHasPrototype is true, the engine never calls these methods:
+   *     has, set, enumerate, iterate.  Instead, for these operations,
+   *     it calls the "own" methods like getOwnPropertyDescriptor, hasOwn,
+   *     defineProperty, getOwnEnumerablePropertyKeys, etc.,
+   *     and consults the prototype chain if needed.
+   *
+   *   - When mHasPrototype is true, the engine calls handler->get() only if
+   *     handler->hasOwn() says an own property exists on the proxy. If not,
+   *     it consults the prototype chain.
+   *
+   * This is useful because it frees the ProxyHandler from having to implement
+   * any behavior having to do with the prototype chain.
+   */
+  bool mHasPrototype;
+
+  /*
+   * All proxies indicate whether they have any sort of interesting security
+   * policy that might prevent the caller from doing something it wants to
+   * the object. In the case of wrappers, this distinction is used to
+   * determine whether the caller may strip off the wrapper if it so desires.
+   */
+  bool mHasSecurityPolicy;
+
+ public:
+  explicit constexpr BaseProxyHandler(const void* aFamily,
+                                      bool aHasPrototype = false,
+                                      bool aHasSecurityPolicy = false)
+      : mFamily(aFamily),
+        mHasPrototype(aHasPrototype),
+        mHasSecurityPolicy(aHasSecurityPolicy) {}
+
+  bool hasPrototype() const { return mHasPrototype; }
+
+  bool hasSecurityPolicy() const { return mHasSecurityPolicy; }
+
+  inline const void* family() const { return mFamily; }
+  static size_t offsetOfFamily() { return offsetof(BaseProxyHandler, mFamily); }
+
+  virtual bool finalizeInBackground(const JS::Value& priv) const {
+    /*
+     * Called on creation of a proxy to determine whether its finalize
+     * method can be finalized on the background thread.
+     */
+    return true;
+  }
+
+  virtual bool canNurseryAllocate() const {
+    /*
+     * Nursery allocation is allowed if and only if it is safe to not
+     * run |finalize| when the ProxyObject dies.
+     */
+    return false;
+  }
+
+  /* Policy enforcement methods.
+   *
+   * enter() allows the policy to specify whether the caller may perform |act|
+   * on the proxy's |id| property. In the case when |act| is CALL, |id| is
+   * generally JSID_VOID.  The |mayThrow| parameter indicates whether a
+   * handler that wants to throw custom exceptions when denying should do so
+   * or not.
+   *
+   * The |act| parameter to enter() specifies the action being performed.
+   * If |bp| is false, the method suggests that the caller throw (though it
+   * may still decide to squelch the error).
+   *
+   * We make these OR-able so that assertEnteredPolicy can pass a union of them.
+   * For example, get{,Own}PropertyDescriptor is invoked by calls to ::get()
+   * ::set(), in addition to being invoked on its own, so there are several
+   * valid Actions that could have been entered.
+   */
+  typedef uint32_t Action;
+  enum {
+    NONE = 0x00,
+    GET = 0x01,
+    SET = 0x02,
+    CALL = 0x04,
+    ENUMERATE = 0x08,
+    GET_PROPERTY_DESCRIPTOR = 0x10
+  };
+
+  virtual bool enter(JSContext* cx, JS::HandleObject wrapper, JS::HandleId id,
+                     Action act, bool mayThrow, bool* bp) const;
+
+  /* Standard internal methods. */
+  virtual bool getOwnPropertyDescriptor(
+      JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+      JS::MutableHandle<JS::PropertyDescriptor> desc) const = 0;
+  virtual bool defineProperty(JSContext* cx, JS::HandleObject proxy,
+                              JS::HandleId id,
+                              JS::Handle<JS::PropertyDescriptor> desc,
+                              JS::ObjectOpResult& result) const = 0;
+  virtual bool ownPropertyKeys(JSContext* cx, JS::HandleObject proxy,
+                               JS::MutableHandleIdVector props) const = 0;
+  virtual bool delete_(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                       JS::ObjectOpResult& result) const = 0;
+
+  /*
+   * These methods are standard, but the engine does not normally call them.
+   * They're opt-in. See "Proxy prototype chains" above.
+   *
+   * getPrototype() crashes if called. setPrototype() throws a TypeError.
+   */
+  virtual bool getPrototype(JSContext* cx, JS::HandleObject proxy,
+                            JS::MutableHandleObject protop) const;
+  virtual bool setPrototype(JSContext* cx, JS::HandleObject proxy,
+                            JS::HandleObject proto,
+                            JS::ObjectOpResult& result) const;
+
+  /* Non-standard but conceptual kin to {g,s}etPrototype, so these live here. */
+  virtual bool getPrototypeIfOrdinary(JSContext* cx, JS::HandleObject proxy,
+                                      bool* isOrdinary,
+                                      JS::MutableHandleObject protop) const = 0;
+  virtual bool setImmutablePrototype(JSContext* cx, JS::HandleObject proxy,
+                                     bool* succeeded) const;
+
+  virtual bool preventExtensions(JSContext* cx, JS::HandleObject proxy,
+                                 JS::ObjectOpResult& result) const = 0;
+  virtual bool isExtensible(JSContext* cx, JS::HandleObject proxy,
+                            bool* extensible) const = 0;
+
+  /*
+   * These standard internal methods are implemented, as a convenience, so
+   * that ProxyHandler subclasses don't have to provide every single method.
+   *
+   * The base-class implementations work by calling getOwnPropertyDescriptor()
+   * and going up the [[Prototype]] chain if necessary. The algorithm for this
+   * follows what is defined for Ordinary Objects in the ES spec.
+   * They do not follow any standard. When in doubt, override them.
+   */
+  virtual bool has(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                   bool* bp) const;
+  virtual bool get(JSContext* cx, JS::HandleObject proxy,
+                   JS::HandleValue receiver, JS::HandleId id,
+                   JS::MutableHandleValue vp) const;
+  virtual bool set(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                   JS::HandleValue v, JS::HandleValue receiver,
+                   JS::ObjectOpResult& result) const;
+
+  // Use the ProxyExpando object for private fields, rather than taking the
+  // normal get/set/defineField paths.
+  virtual bool useProxyExpandoObjectForPrivateFields() const { return true; }
+
+  /*
+   * [[Call]] and [[Construct]] are standard internal methods but according
+   * to the spec, they are not present on every object.
+   *
+   * SpiderMonkey never calls a proxy's call()/construct() internal method
+   * unless isCallable()/isConstructor() returns true for that proxy.
+   *
+   * BaseProxyHandler::isCallable()/isConstructor() always return false, and
+   * BaseProxyHandler::call()/construct() crash if called. So if you're
+   * creating a kind of that is never callable, you don't have to override
+   * anything, but otherwise you probably want to override all four.
+   */
+  virtual bool call(JSContext* cx, JS::HandleObject proxy,
+                    const JS::CallArgs& args) const;
+  virtual bool construct(JSContext* cx, JS::HandleObject proxy,
+                         const JS::CallArgs& args) const;
+
+  /* SpiderMonkey extensions. */
+  virtual bool enumerate(JSContext* cx, JS::HandleObject proxy,
+                         JS::MutableHandleIdVector props) const;
+  virtual bool hasOwn(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                      bool* bp) const;
+  virtual bool getOwnEnumerablePropertyKeys(
+      JSContext* cx, JS::HandleObject proxy,
+      JS::MutableHandleIdVector props) const;
+  virtual bool nativeCall(JSContext* cx, JS::IsAcceptableThis test,
+                          JS::NativeImpl impl, const JS::CallArgs& args) const;
+  virtual bool hasInstance(JSContext* cx, JS::HandleObject proxy,
+                           JS::MutableHandleValue v, bool* bp) const;
+  virtual bool getBuiltinClass(JSContext* cx, JS::HandleObject proxy,
+                               ESClass* cls) const;
+  virtual bool isArray(JSContext* cx, JS::HandleObject proxy,
+                       JS::IsArrayAnswer* answer) const;
+  virtual const char* className(JSContext* cx, JS::HandleObject proxy) const;
+  virtual JSString* fun_toString(JSContext* cx, JS::HandleObject proxy,
+                                 bool isToSource) const;
+  virtual RegExpShared* regexp_toShared(JSContext* cx,
+                                        JS::HandleObject proxy) const;
+  virtual bool boxedValue_unbox(JSContext* cx, JS::HandleObject proxy,
+                                JS::MutableHandleValue vp) const;
+  virtual void trace(JSTracer* trc, JSObject* proxy) const;
+  virtual void finalize(JSFreeOp* fop, JSObject* proxy) const;
+  virtual size_t objectMoved(JSObject* proxy, JSObject* old) const;
+
+  // Allow proxies, wrappers in particular, to specify callability at runtime.
+  // Note: These do not take const JSObject*, but they do in spirit.
+  //       We are not prepared to do this, as there's little const correctness
+  //       in the external APIs that handle proxies.
+  virtual bool isCallable(JSObject* obj) const;
+  virtual bool isConstructor(JSObject* obj) const;
+
+  virtual bool getElements(JSContext* cx, JS::HandleObject proxy,
+                           uint32_t begin, uint32_t end,
+                           ElementAdder* adder) const;
+
+  virtual bool isScripted() const { return false; }
+};
+
+extern JS_FRIEND_DATA const JSClass ProxyClass;
+
+inline bool IsProxy(const JSObject* obj) {
+  return JS::GetClass(obj)->isProxy();
+}
+
+namespace detail {
+
+// Proxy slot layout
+// -----------------
+//
+// Every proxy has a ProxyValueArray that contains the following Values:
+//
+// - The expando slot. This is used to hold private fields should they be
+//   stamped into a non-forwarding proxy type.
+// - The private slot.
+// - The reserved slots. The number of slots is determined by the proxy's Class.
+//
+// Proxy objects store a pointer to the reserved slots (ProxyReservedSlots*).
+// The ProxyValueArray and the private slot can be accessed using
+// ProxyValueArray::fromReservedSlots or ProxyDataLayout::values.
+//
+// Storing a pointer to ProxyReservedSlots instead of ProxyValueArray has a
+// number of advantages. In particular, it means JS::GetReservedSlot and
+// JS::SetReservedSlot can be used with both proxies and native objects. This
+// works because the ProxyReservedSlots* pointer is stored where native objects
+// store their dynamic slots pointer.
+
+struct ProxyReservedSlots {
+  JS::Value slots[1];
+
+  static inline int offsetOfPrivateSlot();
+
+  static inline int offsetOfSlot(size_t slot) {
+    return offsetof(ProxyReservedSlots, slots[0]) + slot * sizeof(JS::Value);
+  }
+
+  void init(size_t nreserved) {
+    for (size_t i = 0; i < nreserved; i++) {
+      slots[i] = JS::UndefinedValue();
+    }
+  }
+
+  ProxyReservedSlots(const ProxyReservedSlots&) = delete;
+  void operator=(const ProxyReservedSlots&) = delete;
+};
+
+struct ProxyValueArray {
+  JS::Value expandoSlot;
+  JS::Value privateSlot;
+  ProxyReservedSlots reservedSlots;
+
+  void init(size_t nreserved) {
+    expandoSlot = JS::ObjectOrNullValue(nullptr);
+    privateSlot = JS::UndefinedValue();
+    reservedSlots.init(nreserved);
+  }
+
+  static size_t sizeOf(size_t nreserved) {
+    return offsetOfReservedSlots() + nreserved * sizeof(JS::Value);
+  }
+  static MOZ_ALWAYS_INLINE ProxyValueArray* fromReservedSlots(
+      ProxyReservedSlots* slots) {
+    uintptr_t p = reinterpret_cast<uintptr_t>(slots);
+    return reinterpret_cast<ProxyValueArray*>(p - offsetOfReservedSlots());
+  }
+  static size_t offsetOfReservedSlots() {
+    return offsetof(ProxyValueArray, reservedSlots);
+  }
+
+  ProxyValueArray(const ProxyValueArray&) = delete;
+  void operator=(const ProxyValueArray&) = delete;
+};
+
+/* static */ inline int ProxyReservedSlots::offsetOfPrivateSlot() {
+  return -int(ProxyValueArray::offsetOfReservedSlots()) +
+         offsetof(ProxyValueArray, privateSlot);
+}
+
+// All proxies share the same data layout. Following the object's shape and
+// type, the proxy has a ProxyDataLayout structure with a pointer to an array
+// of values and the proxy's handler. This is designed both so that proxies can
+// be easily swapped with other objects (via RemapWrapper) and to mimic the
+// layout of other objects (proxies and other objects have the same size) so
+// that common code can access either type of object.
+//
+// See GetReservedOrProxyPrivateSlot below.
+struct ProxyDataLayout {
+  ProxyReservedSlots* reservedSlots;
+  const BaseProxyHandler* handler;
+
+  MOZ_ALWAYS_INLINE ProxyValueArray* values() const {
+    return ProxyValueArray::fromReservedSlots(reservedSlots);
+  }
+};
+
+const uint32_t ProxyDataOffset = 2 * sizeof(void*);
+
+inline ProxyDataLayout* GetProxyDataLayout(JSObject* obj) {
+  MOZ_ASSERT(IsProxy(obj));
+  return reinterpret_cast<ProxyDataLayout*>(reinterpret_cast<uint8_t*>(obj) +
+                                            ProxyDataOffset);
+}
+
+inline const ProxyDataLayout* GetProxyDataLayout(const JSObject* obj) {
+  MOZ_ASSERT(IsProxy(obj));
+  return reinterpret_cast<const ProxyDataLayout*>(
+      reinterpret_cast<const uint8_t*>(obj) + ProxyDataOffset);
+}
+
+JS_FRIEND_API void SetValueInProxy(JS::Value* slot, const JS::Value& value);
+
+inline void SetProxyReservedSlotUnchecked(JSObject* obj, size_t n,
+                                          const JS::Value& extra) {
+  MOZ_ASSERT(n < JSCLASS_RESERVED_SLOTS(JS::GetClass(obj)));
+
+  JS::Value* vp = &GetProxyDataLayout(obj)->reservedSlots->slots[n];
+
+  // Trigger a barrier before writing the slot.
+  if (vp->isGCThing() || extra.isGCThing()) {
+    SetValueInProxy(vp, extra);
+  } else {
+    *vp = extra;
+  }
+}
+
+}  // namespace detail
+
+inline const BaseProxyHandler* GetProxyHandler(const JSObject* obj) {
+  return detail::GetProxyDataLayout(obj)->handler;
+}
+
+inline const JS::Value& GetProxyPrivate(const JSObject* obj) {
+  return detail::GetProxyDataLayout(obj)->values()->privateSlot;
+}
+
+inline const JS::Value& GetProxyExpando(const JSObject* obj) {
+  return detail::GetProxyDataLayout(obj)->values()->expandoSlot;
+}
+
+inline JSObject* GetProxyTargetObject(JSObject* obj) {
+  return GetProxyPrivate(obj).toObjectOrNull();
+}
+
+inline const JS::Value& GetProxyReservedSlot(const JSObject* obj, size_t n) {
+  MOZ_ASSERT(n < JSCLASS_RESERVED_SLOTS(JS::GetClass(obj)));
+  return detail::GetProxyDataLayout(obj)->reservedSlots->slots[n];
+}
+
+inline void SetProxyHandler(JSObject* obj, const BaseProxyHandler* handler) {
+  detail::GetProxyDataLayout(obj)->handler = handler;
+}
+
+inline void SetProxyReservedSlot(JSObject* obj, size_t n,
+                                 const JS::Value& extra) {
+#ifdef DEBUG
+  if (gc::detail::ObjectIsMarkedBlack(obj)) {
+    JS::AssertValueIsNotGray(extra);
+  }
+#endif
+
+  detail::SetProxyReservedSlotUnchecked(obj, n, extra);
+}
+
+inline void SetProxyPrivate(JSObject* obj, const JS::Value& value) {
+#ifdef DEBUG
+  if (gc::detail::ObjectIsMarkedBlack(obj)) {
+    JS::AssertValueIsNotGray(value);
+  }
+#endif
+
+  JS::Value* vp = &detail::GetProxyDataLayout(obj)->values()->privateSlot;
+
+  // Trigger a barrier before writing the slot.
+  if (vp->isGCThing() || value.isGCThing()) {
+    detail::SetValueInProxy(vp, value);
+  } else {
+    *vp = value;
+  }
+}
+
+inline bool IsScriptedProxy(const JSObject* obj) {
+  return IsProxy(obj) && GetProxyHandler(obj)->isScripted();
+}
+
+class MOZ_STACK_CLASS ProxyOptions {
+ protected:
+  /* protected constructor for subclass */
+  explicit ProxyOptions(bool lazyProtoArg)
+      : lazyProto_(lazyProtoArg), clasp_(&ProxyClass) {}
+
+ public:
+  ProxyOptions() : ProxyOptions(false) {}
+
+  bool lazyProto() const { return lazyProto_; }
+  ProxyOptions& setLazyProto(bool flag) {
+    lazyProto_ = flag;
+    return *this;
+  }
+
+  const JSClass* clasp() const { return clasp_; }
+  ProxyOptions& setClass(const JSClass* claspArg) {
+    clasp_ = claspArg;
+    return *this;
+  }
+
+ private:
+  bool lazyProto_;
+  const JSClass* clasp_;
+};
+
+JS_FRIEND_API JSObject* NewProxyObject(
+    JSContext* cx, const BaseProxyHandler* handler, JS::HandleValue priv,
+    JSObject* proto, const ProxyOptions& options = ProxyOptions());
+
+JSObject* RenewProxyObject(JSContext* cx, JSObject* obj,
+                           BaseProxyHandler* handler, const JS::Value& priv);
+
+class JS_FRIEND_API AutoEnterPolicy {
+ public:
+  typedef BaseProxyHandler::Action Action;
+  AutoEnterPolicy(JSContext* cx, const BaseProxyHandler* handler,
+                  JS::HandleObject wrapper, JS::HandleId id, Action act,
+                  bool mayThrow)
+#ifdef JS_DEBUG
+      : context(nullptr)
+#endif
+  {
+    allow = handler->hasSecurityPolicy()
+                ? handler->enter(cx, wrapper, id, act, mayThrow, &rv)
+                : true;
+    recordEnter(cx, wrapper, id, act);
+    // We want to throw an exception if all of the following are true:
+    // * The policy disallowed access.
+    // * The policy set rv to false, indicating that we should throw.
+    // * The caller did not instruct us to ignore exceptions.
+    // * The policy did not throw itself.
+    if (!allow && !rv && mayThrow) {
+      reportErrorIfExceptionIsNotPending(cx, id);
+    }
+  }
+
+  virtual ~AutoEnterPolicy() { recordLeave(); }
+  inline bool allowed() { return allow; }
+  inline bool returnValue() {
+    MOZ_ASSERT(!allowed());
+    return rv;
+  }
+
+ protected:
+  // no-op constructor for subclass
+  AutoEnterPolicy()
+#ifdef JS_DEBUG
+      : context(nullptr),
+        enteredAction(BaseProxyHandler::NONE)
+#endif
+  {
+  }
+  void reportErrorIfExceptionIsNotPending(JSContext* cx, JS::HandleId id);
+  bool allow;
+  bool rv;
+
+#ifdef JS_DEBUG
+  JSContext* context;
+  mozilla::Maybe<JS::HandleObject> enteredProxy;
+  mozilla::Maybe<JS::HandleId> enteredId;
+  Action enteredAction;
+
+  // NB: We explicitly don't track the entered action here, because sometimes
+  // set() methods do an implicit get() during their implementation, leading
+  // to spurious assertions.
+  AutoEnterPolicy* prev;
+  void recordEnter(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                   Action act);
+  void recordLeave();
+
+  friend JS_FRIEND_API void assertEnteredPolicy(JSContext* cx, JSObject* proxy,
+                                                jsid id, Action act);
+#else
+  inline void recordEnter(JSContext* cx, JSObject* proxy, jsid id, Action act) {
+  }
+  inline void recordLeave() {}
+#endif
+
+ private:
+  // This operator needs to be deleted explicitly, otherwise Visual C++ will
+  // create it automatically when it is part of the export JS API. In that
+  // case, compile would fail because HandleId is not allowed to be assigned
+  // and consequently instantiation of assign operator of mozilla::Maybe
+  // would fail. See bug 1325351 comment 16. Copy constructor is removed at
+  // the same time for consistency.
+  AutoEnterPolicy(const AutoEnterPolicy&) = delete;
+  AutoEnterPolicy& operator=(const AutoEnterPolicy&) = delete;
+};
+
+#ifdef JS_DEBUG
+class JS_FRIEND_API AutoWaivePolicy : public AutoEnterPolicy {
+ public:
+  AutoWaivePolicy(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                  BaseProxyHandler::Action act) {
+    allow = true;
+    recordEnter(cx, proxy, id, act);
+  }
+};
+#else
+class JS_FRIEND_API AutoWaivePolicy {
+ public:
+  AutoWaivePolicy(JSContext* cx, JS::HandleObject proxy, JS::HandleId id,
+                  BaseProxyHandler::Action act) {}
+};
+#endif
+
+#ifdef JS_DEBUG
+extern JS_FRIEND_API void assertEnteredPolicy(JSContext* cx, JSObject* obj,
+                                              jsid id,
+                                              BaseProxyHandler::Action act);
+#else
+inline void assertEnteredPolicy(JSContext* cx, JSObject* obj, jsid id,
+                                BaseProxyHandler::Action act) {}
+#endif
+
+extern JS_FRIEND_DATA const JSClassOps ProxyClassOps;
+extern JS_FRIEND_DATA const js::ClassExtension ProxyClassExtension;
+extern JS_FRIEND_DATA const js::ObjectOps ProxyObjectOps;
+
+template <unsigned Flags>
+constexpr unsigned CheckProxyFlags() {
+  constexpr size_t reservedSlots =
+      (Flags >> JSCLASS_RESERVED_SLOTS_SHIFT) & JSCLASS_RESERVED_SLOTS_MASK;
+
+  // For now assert each Proxy Class has at least 1 reserved slot. This is
+  // not a hard requirement, but helps catch Classes that need an explicit
+  // JSCLASS_HAS_RESERVED_SLOTS since bug 1360523.
+  static_assert(reservedSlots > 0,
+                "Proxy Classes must have at least 1 reserved slot");
+
+  constexpr size_t numSlots =
+      offsetof(js::detail::ProxyValueArray, reservedSlots) / sizeof(JS::Value);
+
+  // ProxyValueArray must fit inline in the object, so assert the number of
+  // slots does not exceed MAX_FIXED_SLOTS.
+  static_assert(numSlots + reservedSlots <= JS::shadow::Object::MAX_FIXED_SLOTS,
+                "ProxyValueArray size must not exceed max JSObject size");
+
+  // Proxies must not have the JSCLASS_SKIP_NURSERY_FINALIZE flag set: they
+  // always have finalizers, and whether they can be nursery allocated is
+  // controlled by the canNurseryAllocate() method on the proxy handler.
+  static_assert(!(Flags & JSCLASS_SKIP_NURSERY_FINALIZE),
+                "Proxies must not use JSCLASS_SKIP_NURSERY_FINALIZE; use "
+                "the canNurseryAllocate() proxy handler method instead.");
+  return Flags;
+}
+
+#define PROXY_CLASS_DEF_WITH_CLASS_SPEC(name, flags, classSpec)            \
+  {                                                                        \
+    name,                                                                  \
+        JSClass::NON_NATIVE | JSCLASS_IS_PROXY |                           \
+            JSCLASS_DELAY_METADATA_BUILDER | js::CheckProxyFlags<flags>(), \
+        &js::ProxyClassOps, classSpec, &js::ProxyClassExtension,           \
+        &js::ProxyObjectOps                                                \
+  }
+
+#define PROXY_CLASS_DEF(name, flags) \
+  PROXY_CLASS_DEF_WITH_CLASS_SPEC(name, flags, JS_NULL_CLASS_SPEC)
+
+// Converts a proxy into a DeadObjectProxy that will throw exceptions on all
+// access. This will run the proxy's finalizer to perform clean-up before the
+// conversion happens.
+JS_FRIEND_API void NukeNonCCWProxy(JSContext* cx, JS::HandleObject proxy);
+
+// This is a variant of js::NukeNonCCWProxy() for CCWs. It should only be called
+// on CCWs that have been removed from CCW tables.
+JS_FRIEND_API void NukeRemovedCrossCompartmentWrapper(JSContext* cx,
+                                                      JSObject* wrapper);
+
+} /* namespace js */
+
+#endif /* js_Proxy_h */