js/xpconnect/src/XPCJSID.cpp
author shindli <shindli@mozilla.com>
Thu, 06 Sep 2018 22:12:44 +0300
changeset 490848 8be67ab3d7d34909c6e52b7e6984b6ff84cc470a
parent 490847 d4ae1994c20c1b0fb9051862606f94e7854b86f2
child 490856 38ed8871759e1f1e07fe1684ead6ca34413a6842
permissions -rw-r--r--
Backed out changeset d4ae1994c20c (bug 1489147) for bustages in JSDebugger.cpp on a CLOSED TREE

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
/* vim: set ts=8 sts=4 et sw=4 tw=99: */
/* 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/. */

/* An xpcom implementation of the JavaScript nsIID and nsCID objects. */

#include "xpcprivate.h"
#include "xpc_make_class.h"
#include "mozilla/dom/BindingUtils.h"
#include "mozilla/Attributes.h"
#include "mozilla/jsipc/CrossProcessObjectWrappers.h"
#include "mozilla/StaticPtr.h"

using namespace mozilla::dom;
using namespace JS;

/***************************************************************************/
// nsJSID

NS_IMPL_CLASSINFO(nsJSID, nullptr, 0, NS_JS_ID_CID)
NS_IMPL_ISUPPORTS_CI(nsJSID, nsIJSID)

const char nsJSID::gNoString[] = "";

nsJSID::nsJSID()
    : mID(GetInvalidIID()),
      mNumber(const_cast<char*>(gNoString)),
      mName(const_cast<char*>(gNoString))
{
}

nsJSID::~nsJSID()
{
    if (mNumber && mNumber != gNoString)
        free(mNumber);
    if (mName && mName != gNoString)
        free(mName);
}

void nsJSID::Reset()
{
    mID = GetInvalidIID();

    if (mNumber && mNumber != gNoString)
        free(mNumber);
    if (mName && mName != gNoString)
        free(mName);

    mNumber = mName = nullptr;
}

void
nsJSID::SetName(const char* name)
{
    MOZ_ASSERT(!mName || mName == gNoString, "name already set");
    MOZ_ASSERT(name, "null name");
    mName = NS_xstrdup(name);
}

NS_IMETHODIMP
nsJSID::GetName(char * *aName)
{
    if (!aName)
        return NS_ERROR_NULL_POINTER;

    if (!NameIsSet())
        SetNameToNoString();
    MOZ_ASSERT(mName, "name not set");
    *aName = NS_xstrdup(mName);
    return NS_OK;
}

NS_IMETHODIMP
nsJSID::GetNumber(char * *aNumber)
{
    if (!aNumber)
        return NS_ERROR_NULL_POINTER;

    if (!mNumber) {
        if (!(mNumber = mID.ToString()))
            mNumber = const_cast<char*>(gNoString);
    }

    *aNumber = NS_xstrdup(mNumber);
    return NS_OK;
}

NS_IMETHODIMP_(const nsID*)
nsJSID::GetID()
{
    return &mID;
}

NS_IMETHODIMP
nsJSID::GetValid(bool* aValid)
{
    if (!aValid)
        return NS_ERROR_NULL_POINTER;

    *aValid = IsValid();
    return NS_OK;
}

NS_IMETHODIMP
nsJSID::Equals(nsIJSID* other, bool* _retval)
{
    if (!_retval)
        return NS_ERROR_NULL_POINTER;

    if (!other || mID.Equals(GetInvalidIID())) {
        *_retval = false;
        return NS_OK;
    }

    *_retval = other->GetID()->Equals(mID);
    return NS_OK;
}

NS_IMETHODIMP
nsJSID::Initialize(const char* idString)
{
    if (!idString)
        return NS_ERROR_NULL_POINTER;

    if (*idString != '\0' && mID.Equals(GetInvalidIID())) {
        Reset();

        if (idString[0] == '{') {
            if (mID.Parse(idString)) {
                return NS_OK;
            }

            // error - reset to invalid state
            mID = GetInvalidIID();
        }
    }
    return NS_ERROR_FAILURE;
}

void
nsJSID::InitWithName(const nsID& id, const char* nameString)
{
    MOZ_ASSERT(nameString, "no name");
    Reset();
    mID = id;
    SetName(nameString);
}

// try to use the name, if no name, then use the number
NS_IMETHODIMP
nsJSID::ToString(char** _retval)
{
    if (mName && mName != gNoString)
        return GetName(_retval);

    return GetNumber(_retval);
}

const nsID&
nsJSID::GetInvalidIID() const
{
    // {BB1F47B0-D137-11d2-9841-006008962422}
    static const nsID invalid = {0xbb1f47b0, 0xd137, 0x11d2,
                                  {0x98, 0x41, 0x0, 0x60, 0x8, 0x96, 0x24, 0x22}};
    return invalid;
}

//static
already_AddRefed<nsJSID>
nsJSID::NewID(const char* str)
{
    if (!str) {
        NS_ERROR("no string");
        return nullptr;
    }

    RefPtr<nsJSID> idObj = new nsJSID();
    NS_ENSURE_SUCCESS(idObj->Initialize(str), nullptr);
    return idObj.forget();
}

//static
already_AddRefed<nsJSID>
nsJSID::NewID(const nsID& id)
{
    RefPtr<nsJSID> idObj = new nsJSID();
    idObj->mID = id;
    idObj->mName = nullptr;
    idObj->mNumber = nullptr;
    return idObj.forget();
}


/***************************************************************************/
// Class object support so that we can share prototypes of wrapper

// This class exists just so we can have a shared scriptable helper for
// the nsJSIID class. The instances implement their own helpers. But we
// needed to be able to indicate to the shared prototypes this single flag:
// XPC_SCRIPTABLE_DONT_ENUM_STATIC_PROPS. And having a class to do it is
// the only means we have. Setting this flag on any given instance scriptable
// helper is not sufficient to convey the information that we don't want
// static properties enumerated on the shared proto.

class SharedScriptableHelperForJSIID final : public nsIXPCScriptable
{
    ~SharedScriptableHelperForJSIID() {}
public:
    NS_DECL_ISUPPORTS
    NS_DECL_NSIXPCSCRIPTABLE
    SharedScriptableHelperForJSIID() {}
};

NS_IMPL_ISUPPORTS(SharedScriptableHelperForJSIID,
                  nsIXPCScriptable)

// The nsIXPCScriptable map declaration that will generate stubs for us...
#define XPC_MAP_CLASSNAME SharedScriptableHelperForJSIID
#define XPC_MAP_QUOTED_CLASSNAME "JSIID"
#define XPC_MAP_FLAGS XPC_SCRIPTABLE_ALLOW_PROP_MODS_DURING_RESOLVE
#include "xpc_map_end.h" /* This will #undef the above */

static mozilla::StaticRefPtr<nsIXPCScriptable> gSharedScriptableHelperForJSIID;
static bool gClassObjectsWereInited = false;

static void EnsureClassObjectsInitialized()
{
    if (!gClassObjectsWereInited) {
        gSharedScriptableHelperForJSIID = new SharedScriptableHelperForJSIID();

        gClassObjectsWereInited = true;
    }
}

static nsresult GetSharedScriptableHelperForJSIID(nsIXPCScriptable** helper)
{
    EnsureClassObjectsInitialized();
    nsCOMPtr<nsIXPCScriptable> temp = gSharedScriptableHelperForJSIID.get();
    temp.forget(helper);
    return NS_OK;
}

/******************************************************/

#define NULL_CID                                                              \
{ 0x00000000, 0x0000, 0x0000,                                                 \
  { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 } }

NS_DECL_CI_INTERFACE_GETTER(nsJSIID)
NS_IMPL_CLASSINFO(nsJSIID, GetSharedScriptableHelperForJSIID, 0, NULL_CID)

NS_DECL_CI_INTERFACE_GETTER(nsJSCID)
NS_IMPL_CLASSINFO(nsJSCID, nullptr, 0, NULL_CID)

void xpc_DestroyJSxIDClassObjects()
{
    if (gClassObjectsWereInited) {
        NS_IF_RELEASE(NS_CLASSINFO_NAME(nsJSIID));
        NS_IF_RELEASE(NS_CLASSINFO_NAME(nsJSCID));
        gSharedScriptableHelperForJSIID = nullptr;

        gClassObjectsWereInited = false;
    }
}

/***************************************************************************/

NS_IMPL_QUERY_INTERFACE_CI(nsJSIID,
                           nsIJSID,
                           nsIJSIID,
                           nsIXPCScriptable)

NS_IMPL_ADDREF(nsJSIID)
NS_IMPL_RELEASE(nsJSIID)
NS_IMPL_CI_INTERFACE_GETTER(nsJSIID, nsIJSID, nsIJSIID)

// The nsIXPCScriptable map declaration that will generate stubs for us...
#define XPC_MAP_CLASSNAME         nsJSIID
#define XPC_MAP_QUOTED_CLASSNAME "nsJSIID"
#define XPC_MAP_FLAGS (XPC_SCRIPTABLE_WANT_RESOLVE | \
                       XPC_SCRIPTABLE_WANT_ENUMERATE | \
                       XPC_SCRIPTABLE_WANT_HASINSTANCE | \
                       XPC_SCRIPTABLE_ALLOW_PROP_MODS_DURING_RESOLVE)
#include "xpc_map_end.h" /* This will #undef the above */


nsJSIID::nsJSIID(const nsXPTInterfaceInfo* aInfo)
    : mInfo(aInfo)
{
}

nsJSIID::~nsJSIID() {}

// If mInfo is present we use it and ignore mDetails, else we use mDetails.

NS_IMETHODIMP nsJSIID::GetName(char * *aName)
{
    return mInfo->GetName(aName);
}

NS_IMETHODIMP nsJSIID::GetNumber(char * *aNumber)
{
    char str[NSID_LENGTH];
    const nsIID* id;
    mInfo->GetIIDShared(&id);
    id->ToProvidedString(str);
    *aNumber = (char*) moz_xmemdup(str, NSID_LENGTH);
    return NS_OK;
}

NS_IMETHODIMP_(const nsID*) nsJSIID::GetID()
{
    const nsIID* id;
    mInfo->GetIIDShared(&id);
    return id;
}

NS_IMETHODIMP nsJSIID::GetValid(bool* aValid)
{
    *aValid = true;
    return NS_OK;
}

NS_IMETHODIMP nsJSIID::Equals(nsIJSID* other, bool* _retval)
{
    if (!_retval)
        return NS_ERROR_NULL_POINTER;

    if (!other) {
        *_retval = false;
        return NS_OK;
    }

    mInfo->IsIID(other->GetID(), _retval);
    return NS_OK;
}

NS_IMETHODIMP nsJSIID::Initialize(const char* idString)
{
    return NS_ERROR_FAILURE;
}

NS_IMETHODIMP nsJSIID::ToString(char** _retval)
{
    return mInfo->GetName(_retval);
}

// static
already_AddRefed<nsJSIID>
nsJSIID::NewID(const nsXPTInterfaceInfo* aInfo)
{
    if (!aInfo) {
        NS_ERROR("no info");
        return nullptr;
    }

    if (!aInfo->IsScriptable())
        return nullptr;

    RefPtr<nsJSIID> idObj = new nsJSIID(aInfo);
    return idObj.forget();
}


NS_IMETHODIMP
nsJSIID::Resolve(nsIXPConnectWrappedNative* wrapper,
                 JSContext * cx, JSObject * objArg,
                 jsid idArg, bool* resolvedp,
                 bool* _retval)
{
    RootedObject obj(cx, objArg);
    RootedId id(cx, idArg);
    XPCCallContext ccx(cx);

    RefPtr<XPCNativeInterface> iface =
        XPCNativeInterface::GetNewOrUsed(mInfo);

    if (!iface)
        return NS_OK;

    XPCNativeMember* member = iface->FindMember(id);
    if (member && member->IsConstant()) {
        RootedValue val(cx);
        if (!member->GetConstantValue(ccx, iface, val.address()))
            return NS_ERROR_OUT_OF_MEMORY;

        *resolvedp = true;
        *_retval = JS_DefinePropertyById(cx, obj, id, val,
                                         JSPROP_ENUMERATE | JSPROP_READONLY |
                                         JSPROP_PERMANENT | JSPROP_RESOLVING);
    }

    return NS_OK;
}

NS_IMETHODIMP
nsJSIID::Enumerate(nsIXPConnectWrappedNative* wrapper,
                   JSContext * cx, JSObject * objArg, bool* _retval)
{
    // In this case, let's just eagerly resolve...

    RootedObject obj(cx, objArg);
    XPCCallContext ccx(cx);

    RefPtr<XPCNativeInterface> iface =
        XPCNativeInterface::GetNewOrUsed(mInfo);

    if (!iface)
        return NS_OK;

    uint16_t count = iface->GetMemberCount();
    for (uint16_t i = 0; i < count; i++) {
        XPCNativeMember* member = iface->GetMemberAt(i);
        if (member && member->IsConstant() &&
            !xpc_ForcePropertyResolve(cx, obj, member->GetName())) {
            return NS_ERROR_UNEXPECTED;
        }
    }
    return NS_OK;
}

/*
 * HasInstance hooks need to find an appropriate reflector in order to function
 * properly. There are two complexities that we need to handle:
 *
 * 1 - Cross-compartment wrappers. Chrome uses over 100 compartments, all with
 *     system principal. The success of an instanceof check should not depend
 *     on which compartment an object comes from. At the same time, we want to
 *     make sure we don't unwrap important security wrappers.
 *     CheckedUnwrap does the right thing here.
 *
 * 2 - Prototype chains. Suppose someone creates a vanilla JS object |a| and
 *     sets its __proto__ to some WN |b|. If |b instanceof nsIFoo| returns true,
 *     one would expect |a instanceof nsIFoo| to return true as well, since
 *     instanceof is transitive up the prototype chain in ECMAScript. Moreover,
 *     there's chrome code that relies on this.
 *
 * This static method handles both complexities, returning either an XPCWN, a
 * DOM object, or null. The object may well be cross-compartment from |cx|.
 */
static nsresult
FindObjectForHasInstance(JSContext* cx, HandleObject objArg, MutableHandleObject target)
{
    using namespace mozilla::jsipc;
    RootedObject obj(cx, objArg), proto(cx);
    while (true) {
        // Try the object, or the wrappee if allowed.
        JSObject* o = js::IsWrapper(obj) ? js::CheckedUnwrap(obj, false) : obj;
        if (o && (IS_WN_REFLECTOR(o) || IsDOMObject(o) || IsCPOW(o))) {
            target.set(o);
            return NS_OK;
        }

        // Walk the prototype chain from the perspective of the callee (i.e.
        // respecting Xrays if they exist).
        if (!js::GetObjectProto(cx, obj, &proto))
            return NS_ERROR_FAILURE;
        if (!proto) {
            target.set(nullptr);
            return NS_OK;
        }
        obj = proto;
    }
}

nsresult
xpc::HasInstance(JSContext* cx, HandleObject objArg, const nsID* iid, bool* bp)
{
    *bp = false;

    RootedObject obj(cx);
    nsresult rv = FindObjectForHasInstance(cx, objArg, &obj);
    if (NS_WARN_IF(NS_FAILED(rv)))
        return rv;

    if (!obj)
        return NS_OK;

    if (mozilla::jsipc::IsCPOW(obj))
        return mozilla::jsipc::InstanceOf(obj, iid, bp);

    nsCOMPtr<nsISupports> identity = UnwrapReflectorToISupports(obj);
    if (!identity)
        return NS_OK;

    nsCOMPtr<nsISupports> supp;
    identity->QueryInterface(*iid, getter_AddRefs(supp));
    *bp = supp;

    // Our old HasInstance implementation operated by invoking FindTearOff on
    // XPCWrappedNatives, and various bits of chrome JS came to depend on
    // |instanceof| doing an implicit QI if it succeeds. Do a drive-by QI to
    // preserve that behavior. This is just a compatibility hack, so we don't
    // really care if it fails.
    if (IS_WN_REFLECTOR(obj))
        (void) XPCWrappedNative::Get(obj)->FindTearOff(*iid);

    return NS_OK;
}

NS_IMETHODIMP
nsJSIID::HasInstance(nsIXPConnectWrappedNative* wrapper,
                     JSContext* cx, JSObject * /* unused */,
                     HandleValue val, bool* bp, bool* _retval)
{
    *bp = false;

    if (val.isPrimitive())
        return NS_OK;

    // we have a JSObject
    RootedObject obj(cx, &val.toObject());

    const nsIID* iid;
    mInfo->GetIIDShared(&iid);
    return xpc::HasInstance(cx, obj, iid, bp);
}

/***************************************************************************/

NS_IMPL_QUERY_INTERFACE_CI(nsJSCID,
                           nsIJSID,
                           nsIJSCID,
                           nsIXPCScriptable)

NS_IMPL_ADDREF(nsJSCID)
NS_IMPL_RELEASE(nsJSCID)
NS_IMPL_CI_INTERFACE_GETTER(nsJSCID, nsIJSID, nsIJSCID)

// The nsIXPCScriptable map declaration that will generate stubs for us...
#define XPC_MAP_CLASSNAME         nsJSCID
#define XPC_MAP_QUOTED_CLASSNAME "nsJSCID"
#define XPC_MAP_FLAGS (XPC_SCRIPTABLE_WANT_CONSTRUCT | \
                       XPC_SCRIPTABLE_WANT_HASINSTANCE)
#include "xpc_map_end.h" /* This will #undef the above */

nsJSCID::nsJSCID()  { mDetails = new nsJSID(); }
nsJSCID::~nsJSCID() {}

NS_IMETHODIMP nsJSCID::GetName(char * *aName)
    {ResolveName(); return mDetails->GetName(aName);}

NS_IMETHODIMP nsJSCID::GetNumber(char * *aNumber)
    {return mDetails->GetNumber(aNumber);}

NS_IMETHODIMP_(const nsID*) nsJSCID::GetID()
    {return &mDetails->ID();}

NS_IMETHODIMP nsJSCID::GetValid(bool* aValid)
    {return mDetails->GetValid(aValid);}

NS_IMETHODIMP nsJSCID::Equals(nsIJSID* other, bool* _retval)
    {return mDetails->Equals(other, _retval);}

NS_IMETHODIMP
nsJSCID::Initialize(const char* str)
{
    if (str[0] == '{') {
        NS_ENSURE_SUCCESS(mDetails->Initialize(str), NS_ERROR_FAILURE);
    } else {
        nsCOMPtr<nsIComponentRegistrar> registrar;
        NS_GetComponentRegistrar(getter_AddRefs(registrar));
        NS_ENSURE_TRUE(registrar, NS_ERROR_FAILURE);

        nsCID* cid;
        if (NS_FAILED(registrar->ContractIDToCID(str, &cid)))
            return NS_ERROR_FAILURE;
        mDetails->InitWithName(*cid, str);
        free(cid);
    }
    return NS_OK;
}

NS_IMETHODIMP nsJSCID::ToString(char** _retval)
    {ResolveName(); return mDetails->ToString(_retval);}

void
nsJSCID::ResolveName()
{
    if (!mDetails->NameIsSet())
        mDetails->SetNameToNoString();
}

//static
already_AddRefed<nsJSCID>
nsJSCID::NewID(const char* str)
{
    if (!str) {
        NS_ERROR("no string");
        return nullptr;
    }

    RefPtr<nsJSCID> idObj = new nsJSCID();
    if (NS_FAILED(idObj->Initialize(str)))
        return nullptr;
    return idObj.forget();
}

static const nsID*
GetIIDArg(uint32_t argc, const JS::Value& val, JSContext* cx)
{
    const nsID* iid;

    // If an IID was passed in then use it
    if (argc) {
        JSObject* iidobj;
        if (val.isPrimitive() ||
            !(iidobj = val.toObjectOrNull()) ||
            !(iid = xpc_JSObjectToID(cx, iidobj))) {
            return nullptr;
        }
    } else
        iid = &NS_GET_IID(nsISupports);

    return iid;
}

NS_IMETHODIMP
nsJSCID::CreateInstance(HandleValue iidval, JSContext* cx,
                        uint8_t optionalArgc, MutableHandleValue retval)
{
    if (!mDetails->IsValid())
        return NS_ERROR_XPC_BAD_CID;

    if (NS_FAILED(nsXPConnect::SecurityManager()->CanCreateInstance(cx, mDetails->ID()))) {
        NS_ERROR("how are we not being called from chrome here?");
        return NS_OK;
    }

    // If an IID was passed in then use it
    const nsID* iid = GetIIDArg(optionalArgc, iidval, cx);
    if (!iid)
        return NS_ERROR_XPC_BAD_IID;

    nsCOMPtr<nsIComponentManager> compMgr;
    nsresult rv = NS_GetComponentManager(getter_AddRefs(compMgr));
    if (NS_FAILED(rv))
        return NS_ERROR_UNEXPECTED;

    nsCOMPtr<nsISupports> inst;
    rv = compMgr->CreateInstance(mDetails->ID(), nullptr, *iid, getter_AddRefs(inst));
    MOZ_ASSERT(NS_FAILED(rv) || inst, "component manager returned success, but instance is null!");

    NS_ENSURE_SUCCESS(rv, NS_ERROR_XPC_CI_RETURNED_FAILURE);
    if (!inst) {
      return NS_ERROR_XPC_CI_RETURNED_FAILURE;
    }

    rv = nsContentUtils::WrapNative(cx, inst, iid, retval);
    if (NS_FAILED(rv) || retval.isPrimitive())
        return NS_ERROR_XPC_CANT_CREATE_WN;
    return NS_OK;
}

NS_IMETHODIMP
nsJSCID::GetService(HandleValue iidval, JSContext* cx, uint8_t optionalArgc,
                    MutableHandleValue retval)
{
    if (!mDetails->IsValid())
        return NS_ERROR_XPC_BAD_CID;

    if (NS_FAILED(nsXPConnect::SecurityManager()->CanCreateInstance(cx, mDetails->ID()))) {
        MOZ_ASSERT(JS_IsExceptionPending(cx),
                   "security manager vetoed GetService without setting exception");
        return NS_OK;
    }

    // If an IID was passed in then use it
    const nsID* iid = GetIIDArg(optionalArgc, iidval, cx);
    if (!iid)
        return NS_ERROR_XPC_BAD_IID;

    nsCOMPtr<nsIServiceManager> svcMgr;
    nsresult rv = NS_GetServiceManager(getter_AddRefs(svcMgr));
    if (NS_FAILED(rv))
        return rv;

    nsCOMPtr<nsISupports> srvc;
    rv = svcMgr->GetService(mDetails->ID(), *iid, getter_AddRefs(srvc));
    MOZ_ASSERT(NS_FAILED(rv) || srvc, "service manager returned success, but service is null!");

    NS_ENSURE_SUCCESS(rv, NS_ERROR_XPC_GS_RETURNED_FAILURE);
    if (!srvc) {
        return NS_ERROR_XPC_GS_RETURNED_FAILURE;
    }

    RootedValue v(cx);
    rv = nsContentUtils::WrapNative(cx, srvc, iid, &v);
    if (NS_FAILED(rv) || !v.isObject())
        return NS_ERROR_XPC_CANT_CREATE_WN;

    retval.set(v);
    return NS_OK;
}

NS_IMETHODIMP
nsJSCID::Construct(nsIXPConnectWrappedNative* wrapper,
                   JSContext* cx, JSObject* objArg,
                   const CallArgs& args, bool* _retval)
{
    RootedObject obj(cx, objArg);
    XPCJSRuntime* xpcrt = nsXPConnect::GetRuntimeInstance();
    if (!xpcrt)
        return NS_ERROR_FAILURE;

    // 'push' a call context and call on it
    RootedId name(cx, xpcrt->GetStringID(XPCJSContext::IDX_CREATE_INSTANCE));
    XPCCallContext ccx(cx, obj, nullptr, name, args.length(), args.array(),
                       args.rval().address());

    *_retval = XPCWrappedNative::CallMethod(ccx);
    return NS_OK;
}

NS_IMETHODIMP
nsJSCID::HasInstance(nsIXPConnectWrappedNative* wrapper,
                     JSContext* cx, JSObject * /* unused */,
                     HandleValue val, bool* bp, bool* _retval)
{
    *bp = false;

    if (!val.isObject())
        return NS_OK;

    RootedObject obj(cx, &val.toObject());

    // is this really a native xpcom object with a wrapper?
    RootedObject target(cx);
    nsresult rv = FindObjectForHasInstance(cx, obj, &target);
    if (NS_WARN_IF(NS_FAILED(rv)))
        return rv;

    if (!target || !IS_WN_REFLECTOR(target))
        return NS_OK;

    if (XPCWrappedNative* other_wrapper = XPCWrappedNative::Get(target)) {
        if (nsIClassInfo* ci = other_wrapper->GetClassInfo()) {
            // We consider CID equality to be the thing that matters here.
            // This is perhaps debatable.
            nsID cid;
            if (NS_SUCCEEDED(ci->GetClassIDNoAlloc(&cid)))
                *bp = cid.Equals(mDetails->ID());
        }
    }

    return NS_OK;
}

/***************************************************************************/
// additional utilities...

JSObject*
xpc_NewIDObject(JSContext* cx, HandleObject scope, const nsID& aID)
{
    RootedObject obj(cx);

    nsCOMPtr<nsIJSID> iid = nsJSID::NewID(aID);
    if (iid) {
        nsXPConnect* xpc = nsXPConnect::XPConnect();
        if (xpc) {
            xpc->WrapNative(cx, scope, static_cast<nsISupports*>(iid),
                            NS_GET_IID(nsIJSID), obj.address());
        }
    }
    return obj;
}

// note: returned pointer is only valid while |obj| remains alive!
const nsID*
xpc_JSObjectToID(JSContext* cx, JSObject* obj)
{
    if (!cx || !obj)
        return nullptr;

    // NOTE: this call does NOT addref
    XPCWrappedNative* wrapper = nullptr;
    obj = js::CheckedUnwrap(obj);
    if (obj && IS_WN_REFLECTOR(obj))
        wrapper = XPCWrappedNative::Get(obj);
    if (wrapper &&
        (wrapper->HasInterfaceNoQI(NS_GET_IID(nsIJSID))  ||
         wrapper->HasInterfaceNoQI(NS_GET_IID(nsIJSIID)) ||
         wrapper->HasInterfaceNoQI(NS_GET_IID(nsIJSCID)))) {
        return ((nsIJSID*)wrapper->GetIdentityObject())->GetID();
    }
    return nullptr;
}

bool
xpc_JSObjectIsID(JSContext* cx, JSObject* obj)
{
    MOZ_ASSERT(cx && obj, "bad param");
    // NOTE: this call does NOT addref
    XPCWrappedNative* wrapper = nullptr;
    obj = js::CheckedUnwrap(obj);
    if (obj && IS_WN_REFLECTOR(obj))
        wrapper = XPCWrappedNative::Get(obj);
    return wrapper &&
           (wrapper->HasInterfaceNoQI(NS_GET_IID(nsIJSID))  ||
            wrapper->HasInterfaceNoQI(NS_GET_IID(nsIJSIID)) ||
            wrapper->HasInterfaceNoQI(NS_GET_IID(nsIJSCID)));
}