LCOV - app.info - js/src/gc/Barrier.h

LCOV - code coverage report
| Current view: | directory - js/src/gc - Barrier.h (source / functions) |  | Found | Hit | Coverage |
| Test: | app.info | Lines: | 89 | 80 | 89.9 %
| Date: | 2012-04-07 | Functions: | 204 | 183 | 89.7 %

           1                 : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
           2                 :  * vim: set ts=8 sw=4 et tw=78:
           3                 :  *
           4                 :  * ***** BEGIN LICENSE BLOCK *****
           5                 :  * Version: MPL 1.1/GPL 2.0/LGPL 2.1
           6                 :  *
           7                 :  * The contents of this file are subject to the Mozilla Public License Version
           8                 :  * 1.1 (the "License"); you may not use this file except in compliance with
           9                 :  * the License. You may obtain a copy of the License at
          10                 :  * http://www.mozilla.org/MPL/
          11                 :  *
          12                 :  * Software distributed under the License is distributed on an "AS IS" basis,
          13                 :  * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the License
          14                 :  * for the specific language governing rights and limitations under the
          15                 :  * License.
          16                 :  *
          17                 :  * The Original Code is SpiderMonkey global object code.
          18                 :  *
          19                 :  * The Initial Developer of the Original Code is
          20                 :  * the Mozilla Foundation.
          21                 :  * Portions created by the Initial Developer are Copyright (C) 2011
          22                 :  * the Initial Developer. All Rights Reserved.
          23                 :  *
          24                 :  * Contributor(s):
          25                 :  *
          26                 :  * Alternatively, the contents of this file may be used under the terms of
          27                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
          28                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
          29                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
          30                 :  * of those above. If you wish to allow use of your version of this file only
          31                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
          32                 :  * use your version of this file under the terms of the MPL, indicate your
          33                 :  * decision by deleting the provisions above and replace them with the notice
          34                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
          35                 :  * the provisions above, a recipient may use your version of this file under
          36                 :  * the terms of any one of the MPL, the GPL or the LGPL.
          37                 :  *
          38                 :  * ***** END LICENSE BLOCK ***** */
          39                 :
          40                 : #ifndef jsgc_barrier_h___
          41                 : #define jsgc_barrier_h___
          42                 :
          43                 : #include "jsapi.h"
          44                 : #include "jscell.h"
          45                 :
          46                 : #include "js/HashTable.h"
          47                 :
          48                 : /*
          49                 :  * A write barrier is a mechanism used by incremental or generation GCs to
          50                 :  * ensure that every value that needs to be marked is marked. In general, the
          51                 :  * write barrier should be invoked whenever a write can cause the set of things
          52                 :  * traced through by the GC to change. This includes:
          53                 :  *   - writes to object properties
          54                 :  *   - writes to array slots
          55                 :  *   - writes to fields like JSObject::shape_ that we trace through
          56                 :  *   - writes to fields in private data, like JSGenerator::obj
          57                 :  *   - writes to non-markable fields like JSObject::private that point to
          58                 :  *     markable data
          59                 :  * The last category is the trickiest. Even though the private pointers does not
          60                 :  * point to a GC thing, changing the private pointer may change the set of
          61                 :  * objects that are traced by the GC. Therefore it needs a write barrier.
          62                 :  *
          63                 :  * Every barriered write should have the following form:
          64                 :  *   <pre-barrier>
          65                 :  *   obj->field = value; // do the actual write
          66                 :  *   <post-barrier>
          67                 :  * The pre-barrier is used for incremental GC and the post-barrier is for
          68                 :  * generational GC.
          69                 :  *
          70                 :  *                               PRE-BARRIER
          71                 :  *
          72                 :  * To understand the pre-barrier, let's consider how incremental GC works. The
          73                 :  * GC itself is divided into "slices". Between each slice, JS code is allowed to
          74                 :  * run. Each slice should be short so that the user doesn't notice the
          75                 :  * interruptions. In our GC, the structure of the slices is as follows:
          76                 :  *
          77                 :  * 1. ... JS work, which leads to a request to do GC ...
          78                 :  * 2. [first GC slice, which performs all root marking and possibly more marking]
          79                 :  * 3. ... more JS work is allowed to run ...
          80                 :  * 4. [GC mark slice, which runs entirely in drainMarkStack]
          81                 :  * 5. ... more JS work ...
          82                 :  * 6. [GC mark slice, which runs entirely in drainMarkStack]
          83                 :  * 7. ... more JS work ...
          84                 :  * 8. [GC marking finishes; sweeping done non-incrementally; GC is done]
          85                 :  * 9. ... JS continues uninterrupted now that GC is finishes ...
          86                 :  *
          87                 :  * Of course, there may be a different number of slices depending on how much
          88                 :  * marking is to be done.
          89                 :  *
          90                 :  * The danger inherent in this scheme is that the JS code in steps 3, 5, and 7
          91                 :  * might change the heap in a way that causes the GC to collect an object that
          92                 :  * is actually reachable. The write barrier prevents this from happening. We use
          93                 :  * a variant of incremental GC called "snapshot at the beginning." This approach
          94                 :  * guarantees the invariant that if an object is reachable in step 2, then we
          95                 :  * will mark it eventually. The name comes from the idea that we take a
          96                 :  * theoretical "snapshot" of all reachable objects in step 2; all objects in
          97                 :  * that snapshot should eventually be marked. (Note that the write barrier
          98                 :  * verifier code takes an actual snapshot.)
          99                 :  *
         100                 :  * The basic correctness invariant of a snapshot-at-the-beginning collector is
         101                 :  * that any object reachable at the end of the GC (step 9) must either:
         102                 :  *   (1) have been reachable at the beginning (step 2) and thus in the snapshot
         103                 :  *   (2) or must have been newly allocated, in steps 3, 5, or 7.
         104                 :  * To deal with case (2), any objects allocated during an incremental GC are
         105                 :  * automatically marked black.
         106                 :  *
         107                 :  * This strategy is actually somewhat conservative: if an object becomes
         108                 :  * unreachable between steps 2 and 8, it would be safe to collect it. We won't,
         109                 :  * mainly for simplicity. (Also, note that the snapshot is entirely
         110                 :  * theoretical. We don't actually do anything special in step 2 that we wouldn't
         111                 :  * do in a non-incremental GC.
         112                 :  *
         113                 :  * It's the pre-barrier's job to maintain the snapshot invariant. Consider the
         114                 :  * write "obj->field = value". Let the prior value of obj->field be
         115                 :  * value0. Since it's possible that value0 may have been what obj->field
         116                 :  * contained in step 2, when the snapshot was taken, the barrier marks
         117                 :  * value0. Note that it only does this if we're in the middle of an incremental
         118                 :  * GC. Since this is rare, the cost of the write barrier is usually just an
         119                 :  * extra branch.
         120                 :  *
         121                 :  * In practice, we implement the pre-barrier differently based on the type of
         122                 :  * value0. E.g., see JSObject::writeBarrierPre, which is used if obj->field is
         123                 :  * a JSObject*. It takes value0 as a parameter.
         124                 :  *
         125                 :  *                                POST-BARRIER
         126                 :  *
         127                 :  * These are not yet implemented. Once we get generational GC, they will allow
         128                 :  * us to keep track of pointers from non-nursery space into the nursery.
         129                 :  *
         130                 :  *                            IMPLEMENTATION DETAILS
         131                 :  *
         132                 :  * Since it would be awkward to change every write to memory into a function
         133                 :  * call, this file contains a bunch of C++ classes and templates that use
         134                 :  * operator overloading to take care of barriers automatically. In many cases,
         135                 :  * all that's necessary to make some field be barriered is to replace
         136                 :  *     Type *field;
         137                 :  * with
         138                 :  *     HeapPtr<Type> field;
         139                 :  * There are also special classes HeapValue and HeapId, which barrier js::Value
         140                 :  * and jsid, respectively.
         141                 :  *
         142                 :  * One additional note: not all object writes need to be barriered. Writes to
         143                 :  * newly allocated objects do not need a barrier as long as the GC is not
         144                 :  * allowed to run in between the allocation and the write. In these cases, we
         145                 :  * use the "obj->field.init(value)" method instead of "obj->field = value".
         146                 :  * We use the init naming idiom in many places to signify that a field is being
         147                 :  * assigned for the first time, and that no GCs have taken place between the
         148                 :  * object allocation and the assignment.
         149                 :  */
         150                 :
         151                 : struct JSXML;
         152                 :
         153                 : namespace js {
         154                 :
         155                 : template<class T, typename Unioned = uintptr_t>
         156                 : class HeapPtr
         157                 : {
         158                 :     union {
         159                 :         T *value;
         160                 :         Unioned other;
         161                 :     };
         162                 :
         163                 :   public:
         164        14105425 :     HeapPtr() : value(NULL) {}
         165        46684547 :     explicit HeapPtr(T *v) : value(v) { post(); }
         166          255833 :     explicit HeapPtr(const HeapPtr<T> &v) : value(v.value) { post(); }
         167                 :
         168        14582531 :     ~HeapPtr() { pre(); }
         169                 :
         170                 :     /* Use this to install a ptr into a newly allocated object. */
         171       109431186 :     void init(T *v) {
         172       109431186 :         JS_ASSERT(!IsPoisonedPtr<T>(v));
         173       109431186 :         value = v;
         174       109431186 :         post();
         175       109431186 :     }
         176                 :
         177                 :     /* Use to set the pointer to NULL. */
         178                 :     void clear() {
         179                 :         pre();
         180                 :         value = NULL;
         181                 :     }
         182                 :
         183                 :     /* Use this if the automatic coercion to T* isn't working. */
         184       163460501 :     T *get() const { return value; }
         185                 :
         186                 :     /*
         187                 :      * Use these if you want to change the value without invoking the barrier.
         188                 :      * Obviously this is dangerous unless you know the barrier is not needed.
         189                 :      */
         190        34108503 :     T **unsafeGet() { return &value; }
         191         4507868 :     void unsafeSet(T *v) { value = v; }
         192                 :
         193          292610 :     Unioned *unsafeGetUnioned() { return &other; }
         194                 :
         195        89451153 :     HeapPtr<T, Unioned> &operator=(T *v) {
         196        89451153 :         pre();
         197        89451153 :         JS_ASSERT(!IsPoisonedPtr<T>(v));
         198        89451153 :         value = v;
         199        89451153 :         post();
         200        89451153 :         return *this;
         201                 :     }
         202                 :
         203        10148738 :     HeapPtr<T, Unioned> &operator=(const HeapPtr<T> &v) {
         204        10148738 :         pre();
         205        10148738 :         JS_ASSERT(!IsPoisonedPtr<T>(v.value));
         206        10148738 :         value = v.value;
         207        10148738 :         post();
         208        10148738 :         return *this;
         209                 :     }
         210                 :
         211           89745 :     T &operator*() const { return *value; }
         212       504603626 :     T *operator->() const { return value; }
         213                 :
         214              -1 :     operator T*() const { return value; }
         215                 :
         216                 :   private:
         217       114182422 :     void pre() { T::writeBarrierPre(value); }
         218       260479325 :     void post() { T::writeBarrierPost(value, (void *)&value); }
         219                 :
         220                 :     /* Make this friend so it can access pre() and post(). */
         221                 :     template<class T1, class T2>
         222                 :     friend inline void
         223                 :     BarrieredSetPair(JSCompartment *comp,
         224                 :                      HeapPtr<T1> &v1, T1 *val1,
         225                 :                      HeapPtr<T2> &v2, T2 *val2);
         226                 : };
         227                 :
         228                 : /*
         229                 :  * This is a hack for RegExpStatics::updateFromMatch. It allows us to do two
         230                 :  * barriers with only one branch to check if we're in an incremental GC.
         231                 :  */
         232                 : template<class T1, class T2>
         233                 : static inline void
         234         2253934 : BarrieredSetPair(JSCompartment *comp,
         235                 :                  HeapPtr<T1> &v1, T1 *val1,
         236                 :                  HeapPtr<T2> &v2, T2 *val2)
         237                 : {
         238         2253934 :     if (T1::needWriteBarrierPre(comp)) {
         239               0 :         v1.pre();
         240               0 :         v2.pre();
         241                 :     }
         242         2253934 :     v1.unsafeSet(val1);
         243         2253934 :     v2.unsafeSet(val2);
         244         2253934 :     v1.post();
         245         2253934 :     v2.post();
         246         2253934 : }
         247                 :
         248                 : struct Shape;
         249                 : class BaseShape;
         250                 : namespace types { struct TypeObject; }
         251                 :
         252                 : typedef HeapPtr<JSAtom> HeapPtrAtom;
         253                 : typedef HeapPtr<JSObject> HeapPtrObject;
         254                 : typedef HeapPtr<JSFunction> HeapPtrFunction;
         255                 : typedef HeapPtr<JSString> HeapPtrString;
         256                 : typedef HeapPtr<JSScript> HeapPtrScript;
         257                 : typedef HeapPtr<Shape> HeapPtrShape;
         258                 : typedef HeapPtr<BaseShape> HeapPtrBaseShape;
         259                 : typedef HeapPtr<types::TypeObject> HeapPtrTypeObject;
         260                 : typedef HeapPtr<JSXML> HeapPtrXML;
         261                 :
         262                 : /* Useful for hashtables with a HeapPtr as key. */
         263                 : template<class T>
         264                 : struct HeapPtrHasher
         265                 : {
         266                 :     typedef HeapPtr<T> Key;
         267                 :     typedef T *Lookup;
         268                 :
         269           23529 :     static HashNumber hash(Lookup obj) { return DefaultHasher<T *>::hash(obj); }
         270            8281 :     static bool match(const Key &k, Lookup l) { return k.get() == l; }
         271                 : };
         272                 :
         273                 : /* Specialized hashing policy for HeapPtrs. */
         274                 : template <class T>
         275                 : struct DefaultHasher< HeapPtr<T> >: HeapPtrHasher<T> { };
         276                 :
         277                 : class EncapsulatedValue
         278                 : {
         279                 :   protected:
         280                 :     Value value;
         281                 :
         282                 :     /*
         283                 :      * Ensure that EncapsulatedValue is not constructable, except by our
         284                 :      * implementations.
         285                 :      */
         286                 :     EncapsulatedValue() MOZ_DELETE;
         287                 :     EncapsulatedValue(const EncapsulatedValue &v) MOZ_DELETE;
         288                 :     EncapsulatedValue &operator=(const Value &v) MOZ_DELETE;
         289                 :     EncapsulatedValue &operator=(const EncapsulatedValue &v) MOZ_DELETE;
         290                 :
         291         9549209 :     EncapsulatedValue(const Value &v) : value(v) {}
         292         9619007 :     ~EncapsulatedValue() {}
         293                 :
         294                 :   public:
         295           13500 :     const Value &get() const { return value; }
         296        10025097 :     Value *unsafeGet() { return &value; }
         297       344315222 :     operator const Value &() const { return value; }
         298                 :
         299         4255654 :     bool isUndefined() const { return value.isUndefined(); }
         300         2369115 :     bool isNull() const { return value.isNull(); }
         301         2368980 :     bool isBoolean() const { return value.isBoolean(); }
         302               0 :     bool isTrue() const { return value.isTrue(); }
         303          108221 :     bool isFalse() const { return value.isFalse(); }
         304         2368755 :     bool isNumber() const { return value.isNumber(); }
         305               0 :     bool isInt32() const { return value.isInt32(); }
         306               0 :     bool isDouble() const { return value.isDouble(); }
         307         2378034 :     bool isString() const { return value.isString(); }
         308            1719 :     bool isObject() const { return value.isObject(); }
         309           17400 :     bool isMagic(JSWhyMagic why) const { return value.isMagic(why); }
         310                 :     bool isGCThing() const { return value.isGCThing(); }
         311          172835 :     bool isMarkable() const { return value.isMarkable(); }
         312                 :
         313                 :     bool toBoolean() const { return value.toBoolean(); }
         314                 :     double toNumber() const { return value.toNumber(); }
         315               0 :     int32_t toInt32() const { return value.toInt32(); }
         316               0 :     double toDouble() const { return value.toDouble(); }
         317            6768 :     JSString *toString() const { return value.toString(); }
         318                 :     JSObject &toObject() const { return value.toObject(); }
         319                 :     JSObject *toObjectOrNull() const { return value.toObjectOrNull(); }
         320           85951 :     void *toGCThing() const { return value.toGCThing(); }
         321                 :
         322               0 :     JSGCTraceKind gcKind() const { return value.gcKind(); }
         323                 :
         324         4733145 :     uint64_t asRawBits() const { return value.asRawBits(); }
         325                 :
         326                 : #ifdef DEBUG
         327                 :     JSWhyMagic whyMagic() const { return value.whyMagic(); }
         328                 : #endif
         329                 :
         330                 :     static inline void writeBarrierPre(const Value &v);
         331                 :     static inline void writeBarrierPre(JSCompartment *comp, const Value &v);
         332                 :
         333                 :   protected:
         334                 :     inline void pre();
         335                 :     inline void pre(JSCompartment *comp);
         336                 : };
         337                 :
         338                 : class HeapValue : public EncapsulatedValue
         339                 : {
         340                 :   public:
         341                 :     explicit inline HeapValue();
         342                 :     explicit inline HeapValue(const Value &v);
         343                 :     explicit inline HeapValue(const HeapValue &v);
         344                 :     inline ~HeapValue();
         345                 :
         346                 :     inline void init(const Value &v);
         347                 :     inline void init(JSCompartment *comp, const Value &v);
         348                 :
         349                 :     inline HeapValue &operator=(const Value &v);
         350                 :     inline HeapValue &operator=(const HeapValue &v);
         351                 :
         352                 :     /*
         353                 :      * This is a faster version of operator=. Normally, operator= has to
         354                 :      * determine the compartment of the value before it can decide whether to do
         355                 :      * the barrier. If you already know the compartment, it's faster to pass it
         356                 :      * in.
         357                 :      */
         358                 :     inline void set(JSCompartment *comp, const Value &v);
         359                 :
         360                 :     static inline void writeBarrierPost(const Value &v, void *addr);
         361                 :     static inline void writeBarrierPost(JSCompartment *comp, const Value &v, void *addr);
         362                 :
         363                 :   private:
         364                 :     inline void post();
         365                 :     inline void post(JSCompartment *comp);
         366                 : };
         367                 :
         368                 : class HeapSlot : public EncapsulatedValue
         369                 : {
         370                 :     /*
         371                 :      * Operator= is not valid for HeapSlot because is must take the object and
         372                 :      * slot offset to provide to the post/generational barrier.
         373                 :      */
         374                 :     inline HeapSlot &operator=(const Value &v) MOZ_DELETE;
         375                 :     inline HeapSlot &operator=(const HeapValue &v) MOZ_DELETE;
         376                 :     inline HeapSlot &operator=(const HeapSlot &v) MOZ_DELETE;
         377                 :
         378                 :   public:
         379                 :     explicit inline HeapSlot() MOZ_DELETE;
         380                 :     explicit inline HeapSlot(JSObject *obj, uint32_t slot, const Value &v);
         381                 :     explicit inline HeapSlot(JSObject *obj, uint32_t slot, const HeapSlot &v);
         382                 :     inline ~HeapSlot();
         383                 :
         384                 :     inline void init(JSObject *owner, uint32_t slot, const Value &v);
         385                 :     inline void init(JSCompartment *comp, JSObject *owner, uint32_t slot, const Value &v);
         386                 :
         387                 :     inline void set(JSObject *owner, uint32_t slot, const Value &v);
         388                 :     inline void set(JSCompartment *comp, JSObject *owner, uint32_t slot, const Value &v);
         389                 :
         390                 :     static inline void writeBarrierPost(JSObject *obj, uint32_t slot);
         391                 :     static inline void writeBarrierPost(JSCompartment *comp, JSObject *obj, uint32_t slotno);
         392                 :
         393                 :   private:
         394                 :     inline void post(JSObject *owner, uint32_t slot);
         395                 :     inline void post(JSCompartment *comp, JSObject *owner, uint32_t slot);
         396                 : };
         397                 :
         398                 : /*
         399                 :  * NOTE: This is a placeholder for bug 619558.
         400                 :  *
         401                 :  * Run a post write barrier that encompasses multiple contiguous slots in a
         402                 :  * single step.
         403                 :  */
         404                 : static inline void
         405            1363 : SlotRangeWriteBarrierPost(JSCompartment *comp, JSObject *obj, uint32_t start, uint32_t count)
         406                 : {
         407            1363 : }
         408                 :
         409                 : static inline const Value *
         410          762182 : Valueify(const EncapsulatedValue *array)
         411                 : {
         412                 :     JS_STATIC_ASSERT(sizeof(HeapValue) == sizeof(Value));
         413                 :     JS_STATIC_ASSERT(sizeof(HeapSlot) == sizeof(Value));
         414          762182 :     return (const Value *)array;
         415                 : }
         416                 :
         417                 : class HeapSlotArray
         418                 : {
         419                 :     HeapSlot *array;
         420                 :
         421                 :   public:
         422         1395337 :     HeapSlotArray(HeapSlot *array) : array(array) {}
         423                 :
         424          761877 :     operator const Value *() const { return Valueify(array); }
         425          630957 :     operator HeapSlot *() const { return array; }
         426                 :
         427                 :     HeapSlotArray operator +(int offset) const { return HeapSlotArray(array + offset); }
         428            2503 :     HeapSlotArray operator +(uint32_t offset) const { return HeapSlotArray(array + offset); }
         429                 : };
         430                 :
         431                 : class HeapId
         432                 : {
         433                 :     jsid value;
         434                 :
         435                 :   public:
         436           25698 :     explicit HeapId() : value(JSID_VOID) {}
         437                 :     explicit inline HeapId(jsid id);
         438                 :
         439                 :     inline ~HeapId();
         440                 :
         441                 :     inline void init(jsid id);
         442                 :
         443                 :     inline HeapId &operator=(jsid id);
         444                 :     inline HeapId &operator=(const HeapId &v);
         445                 :
         446       930843451 :     bool operator==(jsid id) const { return value == id; }
         447            3025 :     bool operator!=(jsid id) const { return value != id; }
         448                 :
         449        21934579 :     jsid get() const { return value; }
         450         3672790 :     jsid *unsafeGet() { return &value; }
         451              -1 :     operator jsid() const { return value; }
         452                 :
         453                 :   private:
         454                 :     inline void pre();
         455                 :     inline void post();
         456                 :
         457                 :     HeapId(const HeapId &v);
         458                 : };
         459                 :
         460                 : /*
         461                 :  * Incremental GC requires that weak pointers have read barriers. This is mostly
         462                 :  * an issue for empty shapes stored in JSCompartment. The problem happens when,
         463                 :  * during an incremental GC, some JS code stores one of the compartment's empty
         464                 :  * shapes into an object already marked black. Normally, this would not be a
         465                 :  * problem, because the empty shape would have been part of the initial snapshot
         466                 :  * when the GC started. However, since this is a weak pointer, it isn't. So we
         467                 :  * may collect the empty shape even though a live object points to it. To fix
         468                 :  * this, we mark these empty shapes black whenever they get read out.
         469                 :  */
         470                 : template<class T>
         471                 : class ReadBarriered
         472                 : {
         473                 :     T *value;
         474                 :
         475                 :   public:
         476        32838968 :     ReadBarriered() : value(NULL) {}
         477         6086757 :     ReadBarriered(T *value) : value(value) {}
         478                 :
         479       130475662 :     T *get() const {
         480       130475662 :         if (!value)
         481               0 :             return NULL;
         482       130475662 :         T::readBarrier(value);
         483       130475662 :         return value;
         484                 :     }
         485                 :
         486        88286166 :     operator T*() const { return get(); }
         487                 :
         488                 :     T &operator*() const { return *get(); }
         489        42189496 :     T *operator->() const { return get(); }
         490                 :
         491                 :     T *unsafeGet() { return value; }
         492                 :
         493                 :     void set(T *v) { value = v; }
         494                 :
         495                 :     operator bool() { return !!value; }
         496                 : };
         497                 :
         498                 : class ReadBarrieredValue
         499                 : {
         500                 :     Value value;
         501                 :
         502                 :   public:
         503         1530574 :     ReadBarrieredValue() : value(UndefinedValue()) {}
         504           45145 :     ReadBarrieredValue(const Value &value) : value(value) {}
         505                 :
         506                 :     inline const Value &get() const;
         507                 :     inline operator const Value &() const;
         508                 :
         509                 :     inline JSObject &toObject() const;
         510                 : };
         511                 :
         512                 : }
         513                 :
         514                 : #endif /* jsgc_barrier_h___ */

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