LCOV - code coverage report
Current view: directory - js/src/shell - jsheaptools.cpp (source / functions) Found Hit Coverage
Test: app.info Lines: 182 155 85.2 %
Date: 2012-06-02 Functions: 30 30 100.0 %

       1                 : /* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
       2                 :  * vim: set ts=8 sw=4 et tw=99:
       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 JavaScript heap tools.
      18                 :  *
      19                 :  * The Initial Developer of the Original Code is
      20                 :  * Mozilla Corporation.
      21                 :  * Portions created by the Initial Developer are Copyright (C) 2010
      22                 :  * the Initial Developer. All Rights Reserved.
      23                 :  *
      24                 :  * Contributor(s):
      25                 :  *   Jim Blandy <jimb@mozilla.com>
      26                 :  *
      27                 :  * Alternatively, the contents of this file may be used under the terms of
      28                 :  * either of the GNU General Public License Version 2 or later (the "GPL"),
      29                 :  * or the GNU Lesser General Public License Version 2.1 or later (the "LGPL"),
      30                 :  * in which case the provisions of the GPL or the LGPL are applicable instead
      31                 :  * of those above. If you wish to allow use of your version of this file only
      32                 :  * under the terms of either the GPL or the LGPL, and not to allow others to
      33                 :  * use your version of this file under the terms of the MPL, indicate your
      34                 :  * decision by deleting the provisions above and replace them with the notice
      35                 :  * and other provisions required by the GPL or the LGPL. If you do not delete
      36                 :  * the provisions above, a recipient may use your version of this file under
      37                 :  * the terms of any one of the MPL, the GPL or the LGPL.
      38                 :  *
      39                 :  * ***** END LICENSE BLOCK ***** */
      40                 : 
      41                 : #include <string.h>
      42                 : 
      43                 : #include "jsapi.h"
      44                 : 
      45                 : #include "jsalloc.h"
      46                 : #include "jscntxt.h"
      47                 : #include "jscompartment.h"
      48                 : #include "jsfun.h"
      49                 : #include "jsobj.h"
      50                 : #include "jsprf.h"
      51                 : #include "jsutil.h"
      52                 : 
      53                 : #include "jsobjinlines.h"
      54                 : 
      55                 : using namespace js;
      56                 : 
      57                 : #ifdef DEBUG
      58                 : 
      59                 : 
      60                 : /*** class HeapReverser **************************************************************************/
      61                 : 
      62                 : /*
      63                 :  * A class for constructing a map of the JavaScript heap, with all
      64                 :  * reference edges reversed.
      65                 :  *
      66                 :  * Unfortunately, it's not possible to build the results for findReferences
      67                 :  * while visiting things solely in the order that JS_TraceRuntime and
      68                 :  * JS_TraceChildren reaches them. For example, as you work outward from the
      69                 :  * roots, suppose an edge from thing T reaches a "gray" thing G --- G being gray
      70                 :  * because you're still in the midst of traversing its descendants. At this
      71                 :  * point, you don't know yet whether G will be a referrer or not, and so you
      72                 :  * can't tell whether T should be a referrer either. And you won't visit T
      73                 :  * again.
      74                 :  *
      75                 :  * So we take a brute-force approach. We reverse the entire graph, and then walk
      76                 :  * outward from |target| to the representable objects that refer to it, stopping
      77                 :  * at such objects.
      78                 :  */
      79                 : 
      80                 : /*
      81                 :  * A JSTracer that produces a map of the heap with edges reversed. 
      82                 :  *
      83                 :  * HeapReversers must be allocated in a stack frame. (They contain an AutoArrayRooter,
      84                 :  * and those must be allocated and destroyed in a stack-like order.)
      85                 :  *
      86                 :  * HeapReversers keep all the roots they find in their traversal alive until
      87                 :  * they are destroyed. So you don't need to worry about nodes going away while
      88                 :  * you're using them.
      89                 :  */
      90             540 : class HeapReverser : public JSTracer {
      91                 :   public:
      92                 :     struct Edge;
      93                 : 
      94                 :     /* Metadata for a given Cell we have visited. */
      95        30986208 :     class Node {
      96                 :       public:
      97        17677440 :         Node() { }
      98         3343104 :         Node(JSGCTraceKind kind)
      99         3343104 :           : kind(kind), incoming(), marked(false) { }
     100                 : 
     101                 :         /*
     102                 :          * Move constructor and move assignment. These allow us to store our
     103                 :          * incoming edge Vector in the hash table: Vectors support moves, but
     104                 :          * not assignments or copy construction.
     105                 :          */
     106         9965664 :         Node(MoveRef<Node> rhs)
     107         9965664 :           : kind(rhs->kind), incoming(Move(rhs->incoming)), marked(rhs->marked) { }
     108         9965664 :         Node &operator=(MoveRef<Node> rhs) {
     109         9965664 :             this->~Node();
     110         9965664 :             new(this) Node(rhs);
     111         9965664 :             return *this;
     112                 :         }
     113                 : 
     114                 :         /* What kind of Cell this is. */
     115                 :         JSGCTraceKind kind;
     116                 : 
     117                 :         /*
     118                 :          * A vector of this Cell's incoming edges.
     119                 :          * This must use SystemAllocPolicy because HashMap requires its elements to
     120                 :          * be constructible with no arguments.
     121                 :          */
     122                 :         Vector<Edge, 0, SystemAllocPolicy> incoming;
     123                 : 
     124                 :         /* A mark bit, for other traversals. */
     125                 :         bool marked;
     126                 : 
     127                 :       private:
     128                 :         Node(const Node &);
     129                 :         Node &operator=(const Node &);
     130                 :     };
     131                 : 
     132                 :     /* Metadata for a heap edge we have traversed. */
     133                 :     struct Edge {
     134                 :       public:
     135         4419644 :         Edge(char *name, void *origin) : name(name), origin(origin) { }
     136        10347505 :         ~Edge() { js_free(name); }
     137                 : 
     138                 :         /*
     139                 :          * Move constructor and move assignment. These allow us to live in
     140                 :          * Vectors without needing to copy our name string when the vector is
     141                 :          * resized.
     142                 :          */
     143         5927861 :         Edge(MoveRef<Edge> rhs) : name(rhs->name), origin(rhs->origin) {
     144         5927861 :             rhs->name = NULL;
     145         5927861 :         }
     146                 :         Edge &operator=(MoveRef<Edge> rhs) {
     147                 :             this->~Edge();
     148                 :             new(this) Edge(rhs);
     149                 :             return *this;
     150                 :         }
     151                 : 
     152                 :         /* The name of this heap edge. Owned by this Edge. */
     153                 :         char *name;
     154                 : 
     155                 :         /*
     156                 :          * The Cell from which this edge originates. NULL means a root. This is
     157                 :          * a cell address instead of a Node * because Nodes live in HashMap
     158                 :          * table entries; if the HashMap reallocates its table, all pointers to
     159                 :          * the Nodes it contains would become invalid. You should look up the
     160                 :          * address here in |map| to find its Node.
     161                 :          */
     162                 :         void *origin;
     163                 :     };
     164                 : 
     165                 :     /*
     166                 :      * The result of a reversal is a map from Cells' addresses to Node
     167                 :      * structures describing their incoming edges.
     168                 :      */
     169                 :     typedef HashMap<void *, Node, DefaultHasher<void *>, SystemAllocPolicy> Map;
     170                 :     Map map;
     171                 : 
     172                 :     /* Construct a HeapReverser for |context|'s heap. */
     173             540 :     HeapReverser(JSContext *cx) : rooter(cx, 0, NULL), parent(NULL) {
     174             540 :         JS_TracerInit(this, JS_GetRuntime(cx), traverseEdgeWithThis);
     175             540 :     }
     176                 : 
     177             540 :     bool init() { return map.init(); }
     178                 : 
     179                 :     /* Build a reversed map of the heap in |map|. */
     180                 :     bool reverseHeap();
     181                 : 
     182                 :   private:    
     183                 :     /*
     184                 :      * Conservative scanning can, on a whim, decide that a root is no longer a
     185                 :      * root, and cause bits of our graph to disappear. The 'roots' vector holds
     186                 :      * all the roots we find alive, and 'rooter' keeps them alive until we're
     187                 :      * destroyed.
     188                 :      *
     189                 :      * Note that AutoArrayRooters must be constructed and destroyed in a
     190                 :      * stack-like order, so the same rule applies to this HeapReverser. The
     191                 :      * easiest way to satisfy this requirement is to only allocate HeapReversers
     192                 :      * as local variables in functions, or in types that themselves follow that
     193                 :      * rule. This is kind of dumb, but JSAPI doesn't provide any less restricted
     194                 :      * way to register arrays of roots.
     195                 :      */
     196                 :     Vector<jsval, 0, SystemAllocPolicy> roots;
     197                 :     AutoArrayRooter rooter;
     198                 : 
     199                 :     /*
     200                 :      * Return the name of the most recent edge this JSTracer has traversed. The
     201                 :      * result is allocated with malloc; if we run out of memory, raise an error
     202                 :      * in this HeapReverser's context and return NULL.
     203                 :      *
     204                 :      * This may not be called after that edge's call to traverseEdge has
     205                 :      * returned.
     206                 :      */
     207                 :     char *getEdgeDescription();
     208                 : 
     209                 :     /* Class for setting new parent, and then restoring the original. */
     210                 :     class AutoParent {
     211                 :       public:
     212         3343104 :         AutoParent(HeapReverser *reverser, void *newParent) : reverser(reverser) {
     213         3343104 :             savedParent = reverser->parent;
     214         3343104 :             reverser->parent = newParent;
     215         3343104 :         }
     216         3343104 :         ~AutoParent() {
     217         3343104 :             reverser->parent = savedParent; 
     218         3343104 :         }
     219                 :       private:
     220                 :         HeapReverser *reverser;
     221                 :         void *savedParent;
     222                 :     };
     223                 : 
     224                 :     /* A work item in the stack of nodes whose children we need to traverse. */
     225         7766244 :     struct Child {
     226         3343104 :         Child(void *cell, JSGCTraceKind kind) : cell(cell), kind(kind) { }
     227                 :         void *cell;
     228                 :         JSGCTraceKind kind;
     229                 :     };
     230                 : 
     231                 :     /*
     232                 :      * A stack of work items. We represent the stack explicitly to avoid
     233                 :      * overflowing the C++ stack when traversing long chains of objects.
     234                 :      */
     235                 :     Vector<Child, 0, SystemAllocPolicy> work;
     236                 : 
     237                 :     /* When traverseEdge is called, the Cell and kind at which the edge originated. */
     238                 :     void *parent;
     239                 : 
     240                 :     /* Traverse an edge. */
     241                 :     bool traverseEdge(void *cell, JSGCTraceKind kind);
     242                 : 
     243                 :     /*
     244                 :      * JS_TraceRuntime and JS_TraceChildren don't propagate error returns,
     245                 :      * and out-of-memory errors, by design, don't establish an exception in
     246                 :      * |context|, so traverseEdgeWithThis uses this to communicate the
     247                 :      * result of the traversal to reverseHeap.
     248                 :      */
     249                 :     bool traversalStatus;
     250                 : 
     251                 :     /* Static member function wrapping 'traverseEdge'. */
     252         4419644 :     static void traverseEdgeWithThis(JSTracer *tracer, void **thingp, JSGCTraceKind kind) {
     253         4419644 :         HeapReverser *reverser = static_cast<HeapReverser *>(tracer);
     254         4419644 :         reverser->traversalStatus = reverser->traverseEdge(*thingp, kind);
     255         4419644 :     }
     256                 : 
     257                 :     /* Return a jsval representing a node, if possible; otherwise, return JSVAL_VOID. */
     258         2603264 :     jsval nodeToValue(void *cell, int kind) {
     259         2603264 :         if (kind != JSTRACE_OBJECT)
     260         2581515 :             return JSVAL_VOID;
     261           21749 :         JSObject *object = static_cast<JSObject *>(cell);
     262           21749 :         return OBJECT_TO_JSVAL(object);
     263                 :     }
     264                 : };
     265                 : 
     266                 : bool
     267         4419644 : HeapReverser::traverseEdge(void *cell, JSGCTraceKind kind) {
     268                 :     /* If this is a root, make our own root for it as well. */
     269         4419644 :     if (!parent) {
     270         2603264 :         if (!roots.append(nodeToValue(cell, kind)))
     271               0 :             return false;
     272         2603264 :         rooter.changeArray(roots.begin(), roots.length());
     273                 :     }
     274                 : 
     275                 :     /* Capture this edge before the JSTracer members get overwritten. */
     276         4419644 :     char *edgeDescription = getEdgeDescription();
     277         4419644 :     if (!edgeDescription)
     278               0 :         return false;
     279         8839288 :     Edge e(edgeDescription, parent);
     280                 : 
     281         4419644 :     Map::AddPtr a = map.lookupForAdd(cell);
     282         4419644 :     if (!a) {
     283                 :         /*
     284                 :          * We've never visited this cell before. Add it to the map (thus
     285                 :          * marking it as visited), and put it on the work stack, to be
     286                 :          * visited from the main loop.
     287                 :          */
     288         6686208 :         Node n(kind);
     289         3343104 :         uint32_t generation = map.generation();
     290         6686208 :         if (!map.add(a, cell, Move(n)) ||
     291         3343104 :             !work.append(Child(cell, kind)))
     292               0 :             return false;
     293                 :         /* If the map has been resized, re-check the pointer. */
     294         3343104 :         if (map.generation() != generation)
     295            4860 :             a = map.lookupForAdd(cell);
     296                 :     }
     297                 : 
     298                 :     /* Add this edge to the reversed map. */
     299         4419644 :     return a->value.incoming.append(Move(e));
     300                 : }
     301                 : 
     302                 : bool
     303             540 : HeapReverser::reverseHeap() {
     304                 :     /* Prime the work stack with the roots of collection. */
     305             540 :     JS_TraceRuntime(this);
     306             540 :     if (!traversalStatus)
     307               0 :         return false;
     308                 : 
     309                 :     /* Traverse children until the stack is empty. */
     310         3344184 :     while (!work.empty()) {
     311         3343104 :         const Child child = work.popCopy();
     312         6686208 :         AutoParent autoParent(this, child.cell);
     313         3343104 :         JS_TraceChildren(this, child.cell, child.kind);
     314         3343104 :         if (!traversalStatus)
     315               0 :             return false;
     316                 :     }
     317                 : 
     318             540 :     return true;
     319                 : }
     320                 : 
     321                 : char *
     322         4419644 : HeapReverser::getEdgeDescription()
     323                 : {
     324         4419644 :     if (!debugPrinter && debugPrintIndex == (size_t) -1) {
     325         4051559 :         const char *arg = static_cast<const char *>(debugPrintArg);
     326         4051559 :         char *name = static_cast<char *>(js_malloc(strlen(arg) + 1));
     327         4051559 :         if (!name)
     328               0 :             return NULL;
     329         4051559 :         strcpy(name, arg);
     330         4051559 :         return name;
     331                 :     }
     332                 : 
     333                 :     /* Lovely; but a fixed size is required by JSTraceNamePrinter. */
     334                 :     static const int nameSize = 200;
     335          368085 :     char *name = static_cast<char *>(js_malloc(nameSize));
     336          368085 :     if (!name)
     337               0 :         return NULL;
     338          368085 :     if (debugPrinter)
     339          359079 :         debugPrinter(this, name, nameSize);
     340                 :     else
     341                 :         JS_snprintf(name, nameSize, "%s[%lu]",
     342            9006 :                     static_cast<const char *>(debugPrintArg), debugPrintIndex);
     343                 : 
     344                 :     /* Shrink storage to fit. */
     345          368085 :     return static_cast<char *>(js_realloc(name, strlen(name) + 1));
     346                 : }
     347                 : 
     348                 : 
     349                 : /*** class ReferenceFinder ***********************************************************************/
     350                 : 
     351                 : /* A class for finding an object's referrers, given a reversed heap map. */
     352                 : class ReferenceFinder {
     353                 :   public:
     354             540 :     ReferenceFinder(JSContext *cx, const HeapReverser &reverser) 
     355             540 :       : context(cx), reverser(reverser) { }
     356                 : 
     357                 :     /* Produce an object describing all references to |target|. */
     358                 :     JSObject *findReferences(JSObject *target);
     359                 : 
     360                 :   private:
     361                 :     /* The context in which to do allocation and error-handling. */
     362                 :     JSContext *context;
     363                 : 
     364                 :     /* A reversed map of the current heap. */
     365                 :     const HeapReverser &reverser;
     366                 : 
     367                 :     /* The results object we're currently building. */
     368                 :     JSObject *result;
     369                 : 
     370                 :     /* A list of edges we've traversed to get to a certain point. */
     371                 :     class Path {
     372                 :       public:
     373            4085 :         Path(const HeapReverser::Edge &edge, Path *next) : edge(edge), next(next) { }
     374                 :         
     375                 :         /*
     376                 :          * Compute the full path represented by this Path. The result is
     377                 :          * owned by the caller.
     378                 :          */
     379                 :         char *computeName(JSContext *cx);
     380                 : 
     381                 :       private:
     382                 :         const HeapReverser::Edge &edge;
     383                 :         Path *next;
     384                 :     };
     385                 : 
     386                 :     struct AutoNodeMarker {
     387             540 :         AutoNodeMarker(HeapReverser::Node *node) : node(node) { node->marked = true; }
     388             540 :         ~AutoNodeMarker() { node->marked = false; }
     389                 :       private:
     390                 :         HeapReverser::Node *node;
     391                 :     };
     392                 : 
     393                 :     /* 
     394                 :      * Given that we've reached |cell| via |path|, with all Nodes along that
     395                 :      * path marked, add paths from all reportable objects reachable from cell
     396                 :      * to |result|.
     397                 :      */
     398                 :     bool visit(void *cell, Path *path);
     399                 : 
     400                 :     /*
     401                 :      * If |cell|, of |kind|, is representable as a JavaScript value, return that
     402                 :      * value; otherwise, return JSVAL_VOID.
     403                 :      */
     404            1362 :     jsval representable(void *cell, int kind) {
     405            1362 :         if (kind == JSTRACE_OBJECT) {
     406            1362 :             JSObject *object = static_cast<JSObject *>(cell);
     407                 : 
     408                 :             /* Certain classes of object are for internal use only. */
     409            5448 :             if (object->isBlock() ||
     410            1362 :                 object->isCall() ||
     411            1362 :                 object->isWith() ||
     412            1362 :                 object->isDeclEnv()) {
     413               0 :                 return JSVAL_VOID;
     414                 :             }
     415                 : 
     416                 :             /* Internal function objects should also not be revealed. */
     417            1362 :             if (JS_ObjectIsFunction(context, object) && IsInternalFunctionObject(object))
     418               0 :                 return JSVAL_VOID;
     419                 : 
     420            1362 :             return OBJECT_TO_JSVAL(object);
     421                 :         }
     422                 : 
     423               0 :         return JSVAL_VOID;
     424                 :     }
     425                 : 
     426                 :     /* Add |referrer| as something that refers to |target| via |path|. */
     427                 :     bool addReferrer(jsval referrer, Path *path);
     428                 : };
     429                 : 
     430                 : bool
     431            4625 : ReferenceFinder::visit(void *cell, Path *path)
     432                 : {
     433                 :     /* In ReferenceFinder, paths will almost certainly fit on the C++ stack. */
     434            4625 :     JS_CHECK_RECURSION(context, return false);
     435                 : 
     436                 :     /* Have we reached a root? Always report that. */
     437            4625 :     if (!cell)
     438            2723 :         return addReferrer(JSVAL_NULL, path);
     439                 :         
     440            1902 :     HeapReverser::Map::Ptr p = reverser.map.lookup(cell);
     441            1902 :     JS_ASSERT(p);
     442            1902 :     HeapReverser::Node *node = &p->value;
     443                 : 
     444                 :     /* Is |cell| a representable cell, reached via a non-empty path? */
     445            1902 :     if (path != NULL) {
     446            1362 :         jsval representation = representable(cell, node->kind);
     447            1362 :         if (!JSVAL_IS_VOID(representation))
     448            1362 :             return addReferrer(representation, path);
     449                 :     }
     450                 : 
     451                 :     /*
     452                 :      * If we've made a cycle, don't traverse further. We *do* want to include
     453                 :      * paths from the target to itself, so we don't want to do this check until
     454                 :      * after we've possibly reported this cell as a referrer.
     455                 :      */
     456             540 :     if (node->marked)
     457               0 :         return true;
     458            1080 :     AutoNodeMarker marker(node);
     459                 : 
     460                 :     /* Visit the origins of all |cell|'s incoming edges. */
     461            4625 :     for (size_t i = 0; i < node->incoming.length(); i++) {
     462            4085 :         const HeapReverser::Edge &edge = node->incoming[i];
     463            4085 :         Path extendedPath(edge, path);
     464            4085 :         if (!visit(edge.origin, &extendedPath))
     465               0 :             return false;
     466                 :     }
     467                 : 
     468             540 :     return true;
     469                 : }
     470                 : 
     471                 : char *
     472            4085 : ReferenceFinder::Path::computeName(JSContext *cx)
     473                 : {
     474                 :     /* Walk the edge list and compute the total size of the path. */
     475            4085 :     size_t size = 6;
     476            8170 :     for (Path *l = this; l; l = l->next) 
     477            4085 :         size += strlen(l->edge.name) + (l->next ? 2 : 0);
     478            4085 :     size += 1;
     479                 : 
     480            4085 :     char *path = static_cast<char *>(cx->malloc_(size));
     481            4085 :     if (!path)
     482               0 :         return NULL;
     483                 : 
     484                 :     /*
     485                 :      * Walk the edge list again, and copy the edge names into place, with
     486                 :      * appropriate separators. Note that we constructed the edge list from
     487                 :      * target to referrer, which means that the list links point *towards* the
     488                 :      * target, so we can walk the list and build the path from left to right.
     489                 :      */
     490            4085 :     strcpy(path, "edge: ");
     491            4085 :     char *next = path + 6;
     492            8170 :     for (Path *l = this; l; l = l->next) {
     493            4085 :         strcpy(next, l->edge.name);
     494            4085 :         next += strlen(next);
     495            4085 :         if (l->next) {
     496               0 :             strcpy(next, "; ");
     497               0 :             next += 2;
     498                 :         }
     499                 :     }
     500            4085 :     JS_ASSERT(next + 1 == path + size);
     501                 : 
     502            4085 :     return path;
     503                 : }
     504                 : 
     505                 : bool
     506            4085 : ReferenceFinder::addReferrer(jsval referrer, Path *path)
     507                 : {
     508            4085 :     if (!context->compartment->wrap(context, &referrer))
     509               0 :         return NULL;
     510                 : 
     511            4085 :     char *pathName = path->computeName(context);
     512            4085 :     if (!pathName)
     513               0 :         return false;
     514            8170 :     AutoReleasePtr releasePathName(context, pathName);
     515                 : 
     516                 :     /* Find the property of the results object named |pathName|. */
     517                 :     jsval v;
     518            4085 :     if (!JS_GetProperty(context, result, pathName, &v))
     519               0 :         return false;
     520            4085 :     if (JSVAL_IS_VOID(v)) {
     521                 :         /* Create an array to accumulate referents under this path. */
     522            2982 :         JSObject *array = JS_NewArrayObject(context, 1, &referrer);
     523            2982 :         if (!array)
     524               0 :             return false;
     525            2982 :         v = OBJECT_TO_JSVAL(array);
     526            2982 :         return !!JS_SetProperty(context, result, pathName, &v);
     527                 :     }
     528                 : 
     529                 :     /* The property's value had better be an array. */
     530            1103 :     JS_ASSERT(JSVAL_IS_OBJECT(v) && !JSVAL_IS_NULL(v));
     531            1103 :     JSObject *array = JSVAL_TO_OBJECT(v);
     532            1103 :     JS_ASSERT(JS_IsArrayObject(context, array));
     533                 : 
     534                 :     /* Append our referrer to this array. */
     535                 :     uint32_t length;
     536            1103 :     return JS_GetArrayLength(context, array, &length) &&
     537            1103 :            JS_SetElement(context, array, length, &referrer);
     538                 : }
     539                 : 
     540                 : JSObject *
     541             540 : ReferenceFinder::findReferences(JSObject *target)
     542                 : {
     543             540 :     result = JS_NewObject(context, NULL, NULL, NULL);
     544             540 :     if (!result)
     545               0 :         return NULL;
     546             540 :     if (!visit(target, NULL))
     547               0 :         return NULL;
     548                 : 
     549             540 :     return result;
     550                 : }
     551                 : 
     552                 : /* See help(findReferences). */
     553                 : JSBool
     554             540 : FindReferences(JSContext *cx, unsigned argc, jsval *vp)
     555                 : {
     556             540 :     if (argc < 1) {
     557                 :         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_MORE_ARGS_NEEDED,
     558               0 :                              "findReferences", "0", "s");
     559               0 :         return false;
     560                 :     }
     561                 : 
     562             540 :     jsval target = JS_ARGV(cx, vp)[0];
     563             540 :     if (!JSVAL_IS_OBJECT(target) || JSVAL_IS_NULL(target)) {
     564                 :         JS_ReportErrorNumber(cx, js_GetErrorMessage, NULL, JSMSG_UNEXPECTED_TYPE,
     565               0 :                              "argument", "not an object");
     566               0 :         return false;
     567                 :     }
     568                 : 
     569                 :     /* Walk the JSRuntime, producing a reversed map of the heap. */
     570            1080 :     HeapReverser reverser(cx);
     571             540 :     if (!reverser.init() || !reverser.reverseHeap())
     572               0 :         return false;
     573                 : 
     574                 :     /* Given the reversed map, find the referents of target. */
     575             540 :     ReferenceFinder finder(cx, reverser);
     576             540 :     JSObject *references = finder.findReferences(JSVAL_TO_OBJECT(target));
     577             540 :     if (!references)
     578               0 :         return false;
     579                 :     
     580             540 :     JS_SET_RVAL(cx, vp, OBJECT_TO_JSVAL(references));
     581             540 :     return true;
     582                 : }
     583                 : 
     584                 : #endif /* DEBUG */

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