diff --git a/js/src/jscntxt.cpp b/js/src/jscntxt.cpp
index ac3a1ed2d11..57820d666c7 100644
--- a/js/src/jscntxt.cpp
+++ b/js/src/jscntxt.cpp
@@ -585,20 +585,16 @@ js_DestroyContext(JSContext *cx, JSDestroyContextMode mode)
              */
             {
                 AutoLockGC lock(rt);
-                JSCompartment **compartment = rt->compartments.begin();
-                JSCompartment **end = rt->compartments.end();
-                while (compartment < end) {
-                    (*compartment)->types.print(cx, false);
-                    compartment++;
-                }
+                for (CompartmentsIter c(rt); !c.done(); c.next())
+                    c->types.print(cx, false);
             }
 
             /* Unpin all common atoms before final GC. */
             js_FinishCommonAtoms(cx);
 
             /* Clear debugging state to remove GC roots. */
-            for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); c++)
-                (*c)->clearTraps(cx, NULL);
+            for (CompartmentsIter c(rt); !c.done(); c.next())
+                c->clearTraps(cx, NULL);
             JS_ClearAllWatchPoints(cx);
         }
 
diff --git a/js/src/jscompartment.h b/js/src/jscompartment.h
index 66aaa96aad5..397e9ae51bf 100644
--- a/js/src/jscompartment.h
+++ b/js/src/jscompartment.h
@@ -833,6 +833,32 @@ class ErrorCopier
     ~ErrorCopier();
 };
 
+class CompartmentsIter {
+  private:
+    JSCompartment **it, **end;
+
+  public:
+    CompartmentsIter(JSRuntime *rt) {
+        it = rt->compartments.begin();
+        end = rt->compartments.end();
+    }
+
+    bool done() const { return it == end; }
+
+    void next() {
+        JS_ASSERT(!done());
+        it++;
+    }
+
+    JSCompartment *get() const {
+        JS_ASSERT(!done());
+        return *it;
+    }
+
+    operator JSCompartment *() const { return get(); }
+    JSCompartment *operator->() const { return get(); }
+};
+
 } /* namespace js */
 
 #endif /* jscompartment_h___ */
diff --git a/js/src/jsgc.cpp b/js/src/jsgc.cpp
index b1e3a53fc42..8858acc6d4c 100644
--- a/js/src/jsgc.cpp
+++ b/js/src/jsgc.cpp
@@ -1143,8 +1143,8 @@ void
 js_FinishGC(JSRuntime *rt)
 {
     /* Delete all remaining Compartments. */
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c)
-        Foreground::delete_(*c);
+    for (CompartmentsIter c(rt); !c.done(); c.next())
+        Foreground::delete_(c.get());
     rt->compartments.clear();
     rt->atomsCompartment = NULL;
 
@@ -2506,8 +2506,8 @@ BeginMarkPhase(JSContext *cx, GCMarker *gcmarker, JSGCInvocationKind gckind)
         r.front()->bitmap.clear();
 
     if (rt->gcCurrentCompartment) {
-        for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c)
-            (*c)->markCrossCompartmentWrappers(gcmarker);
+        for (CompartmentsIter c(rt); !c.done(); c.next())
+            c->markCrossCompartmentWrappers(gcmarker);
         Debugger::markCrossCompartmentDebuggerObjectReferents(gcmarker);
     }
 
@@ -2545,9 +2545,9 @@ EndMarkPhase(JSContext *cx, GCMarker *gcmarker, JSGCInvocationKind gckind)
 #ifdef DEBUG
     /* Make sure that we didn't mark an object in another compartment */
     if (rt->gcCurrentCompartment) {
-        for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-            JS_ASSERT_IF(*c != rt->gcCurrentCompartment && *c != rt->atomsCompartment,
-                         (*c)->arenas.checkArenaListAllUnmarked());
+        for (CompartmentsIter c(rt); !c.done(); c.next()) {
+            JS_ASSERT_IF(c != rt->gcCurrentCompartment && c != rt->atomsCompartment,
+                         c->arenas.checkArenaListAllUnmarked());
         }
     }
 #endif
@@ -2956,8 +2956,8 @@ GCCycle(JSContext *cx, JSCompartment *comp, JSGCInvocationKind gckind)
     rt->gcCurrentCompartment = NULL;
     rt->gcWeakMapList = NULL;
 
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c)
-        (*c)->setGCLastBytes((*c)->gcBytes, gckind);
+    for (CompartmentsIter c(rt); !c.done(); c.next())
+        c->setGCLastBytes(c->gcBytes, gckind);
 }
 
 void
@@ -3037,13 +3037,13 @@ class AutoCopyFreeListToArenas {
   public:
     AutoCopyFreeListToArenas(JSRuntime *rt)
       : rt(rt) {
-        for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c)
-            (*c)->arenas.copyFreeListsToArenas();
+        for (CompartmentsIter c(rt); !c.done(); c.next())
+            c->arenas.copyFreeListsToArenas();
     }
 
     ~AutoCopyFreeListToArenas() {
-        for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c)
-            (*c)->arenas.clearFreeListsInArenas();
+        for (CompartmentsIter c(rt); !c.done(); c.next())
+            c->arenas.clearFreeListsInArenas();
     }
 };
 
@@ -3130,16 +3130,15 @@ IterateCompartmentsArenasCells(JSContext *cx, void *data,
     AutoUnlockGC unlock(rt);
 
     AutoCopyFreeListToArenas copy(rt);
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-        JSCompartment *compartment = *c;
-        (*compartmentCallback)(cx, data, compartment);
+    for (CompartmentsIter c(rt); !c.done(); c.next()) {
+        (*compartmentCallback)(cx, data, c);
 
         for (size_t thingKind = 0; thingKind != FINALIZE_LIMIT; thingKind++) {
             JSGCTraceKind traceKind = MapAllocToTraceKind(AllocKind(thingKind));
             size_t thingSize = Arena::thingSize(AllocKind(thingKind));
             IterateArenaCallbackOp arenaOp(cx, data, arenaCallback, traceKind, thingSize);
             IterateCellCallbackOp cellOp(cx, data, cellCallback, traceKind, thingSize);
-            ForEachArenaAndCell(compartment, AllocKind(thingKind), arenaOp, cellOp);
+            ForEachArenaAndCell(c, AllocKind(thingKind), arenaOp, cellOp);
         }
     }
 }
@@ -3193,8 +3192,8 @@ IterateCells(JSContext *cx, JSCompartment *compartment, AllocKind thingKind,
         for (CellIterUnderGC i(compartment, thingKind); !i.done(); i.next())
             cellCallback(cx, data, i.getCell(), traceKind, thingSize);
     } else {
-        for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-            for (CellIterUnderGC i(*c, thingKind); !i.done(); i.next())
+        for (CompartmentsIter c(rt); !c.done(); c.next()) {
+            for (CellIterUnderGC i(c, thingKind); !i.done(); i.next())
                 cellCallback(cx, data, i.getCell(), traceKind, thingSize);
         }
     }
@@ -3413,10 +3412,10 @@ StartVerifyBarriers(JSContext *cx)
      * code in the compartment.
      */
 #ifdef JS_METHODJIT
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-        mjit::ClearAllFrames(*c);
+    for (CompartmentsIter c(rt); !c.done(); c.next()) {
+        mjit::ClearAllFrames(c);
 
-        for (CellIterUnderGC i(*c, FINALIZE_SCRIPT); !i.done(); i.next()) {
+        for (CellIterUnderGC i(c, FINALIZE_SCRIPT); !i.done(); i.next()) {
             JSScript *script = i.get<JSScript>();
             mjit::ReleaseScriptCode(cx, script);
 
@@ -3474,9 +3473,9 @@ StartVerifyBarriers(JSContext *cx)
 
     rt->gcVerifyData = trc;
     rt->gcIncrementalTracer = &trc->gcmarker;
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-        (*c)->gcIncrementalTracer = &trc->gcmarker;
-        (*c)->needsBarrier_ = true;
+    for (CompartmentsIter c(rt); !c.done(); c.next()) {
+        c->gcIncrementalTracer = &trc->gcmarker;
+        c->needsBarrier_ = true;
     }
 
     return;
@@ -3545,9 +3544,9 @@ EndVerifyBarriers(JSContext *cx)
 
     rt->gcVerifyData = NULL;
     rt->gcIncrementalTracer = NULL;
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-        (*c)->gcIncrementalTracer = NULL;
-        (*c)->needsBarrier_ = false;
+    for (CompartmentsIter c(rt); !c.done(); c.next()) {
+        c->gcIncrementalTracer = NULL;
+        c->needsBarrier_ = false;
     }
 
     JS_TRACER_INIT(trc, cx, CheckAutorooter);
diff --git a/js/src/jspropertytree.cpp b/js/src/jspropertytree.cpp
index bec0df45808..14bb3f8cd6e 100644
--- a/js/src/jspropertytree.cpp
+++ b/js/src/jspropertytree.cpp
@@ -351,14 +351,14 @@ js::PropertyTree::dumpShapes(JSContext *cx)
     JSRuntime *rt = cx->runtime;
     fprintf(dumpfp, "rt->gcNumber = %lu", (unsigned long)rt->gcNumber);
 
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-        if (rt->gcCurrentCompartment != NULL && rt->gcCurrentCompartment != *c)
+    for (CompartmentsIter c(rt); !c.done(); c.next()) {
+        if (rt->gcCurrentCompartment != NULL && rt->gcCurrentCompartment != c)
             continue;
 
-        fprintf(dumpfp, "*** Compartment %p ***\n", (void *)*c);
+        fprintf(dumpfp, "*** Compartment %p ***\n", (void *)c.get());
 
         typedef JSCompartment::EmptyShapeSet HS;
-        HS &h = (*c)->emptyShapes;
+        HS &h = c->emptyShapes;
         for (HS::Range r = h.all(); !r.empty(); r.popFront()) {
             Shape *empty = r.front();
             empty->dumpSubtree(cx, 0, dumpfp);
diff --git a/js/src/jswatchpoint.cpp b/js/src/jswatchpoint.cpp
index d7e54a1f003..ce719b4f09b 100644
--- a/js/src/jswatchpoint.cpp
+++ b/js/src/jswatchpoint.cpp
@@ -184,9 +184,9 @@ WatchpointMap::markAllIteratively(JSTracer *trc)
     }
 
     bool mutated = false;
-    for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-        if ((*c)->watchpointMap)
-            mutated |= (*c)->watchpointMap->markIteratively(trc);
+    for (CompartmentsIter c(rt); !c.done(); c.next()) {
+        if (c->watchpointMap)
+            mutated |= c->watchpointMap->markIteratively(trc);
     }
     return mutated;
 }
@@ -226,8 +226,8 @@ WatchpointMap::sweepAll(JSContext *cx)
         if (WatchpointMap *wpmap = rt->gcCurrentCompartment->watchpointMap)
             wpmap->sweep(cx);
     } else {
-        for (JSCompartment **c = rt->compartments.begin(); c != rt->compartments.end(); ++c) {
-            if (WatchpointMap *wpmap = (*c)->watchpointMap)
+        for (CompartmentsIter c(rt); !c.done(); c.next()) {
+            if (WatchpointMap *wpmap = c->watchpointMap)
                 wpmap->sweep(cx);
         }
     }