The Tor Browser: js/src/gc/RootMarking.cpp@6474c204b198 (annotated)

js/src/gc/RootMarking.cpp@6474c204b198 (annotated)

js/src/gc/RootMarking.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* -*- 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/. */
 #include "mozilla/ArrayUtils.h"
 #ifdef MOZ_VALGRIND
 # include <valgrind/memcheck.h>
 #endif
 #include "jscntxt.h"
 #include "jsgc.h"
 #include "jsonparser.h"
 #include "jsprf.h"
 #include "jstypes.h"
 #include "jswatchpoint.h"
 #include "builtin/MapObject.h"
 #include "frontend/BytecodeCompiler.h"
 #include "gc/GCInternals.h"
 #include "gc/Marking.h"
 #ifdef JS_ION
 # include "jit/IonMacroAssembler.h"
 #endif
 #include "js/HashTable.h"
 #include "vm/Debugger.h"
 #include "jsgcinlines.h"
 #include "jsobjinlines.h"
 using namespace js;
 using namespace js::gc;
 using mozilla::ArrayEnd;
 typedef RootedValueMap::Range RootRange;
 typedef RootedValueMap::Entry RootEntry;
 typedef RootedValueMap::Enum RootEnum;
 #ifdef JSGC_USE_EXACT_ROOTING
 static inline void
 MarkExactStackRoot(JSTracer *trc, Rooted<void*> *rooter, ThingRootKind kind)
 {
     void **addr = (void **)rooter->address();
     if (IsNullTaggedPointer(*addr))
         return;
     if (kind == THING_ROOT_OBJECT && *addr == TaggedProto::LazyProto)
         return;
     switch (kind) {
       case THING_ROOT_OBJECT:      MarkObjectRoot(trc, (JSObject **)addr, "exact-object"); break;
       case THING_ROOT_STRING:      MarkStringRoot(trc, (JSString **)addr, "exact-string"); break;
       case THING_ROOT_SCRIPT:      MarkScriptRoot(trc, (JSScript **)addr, "exact-script"); break;
       case THING_ROOT_LAZY_SCRIPT: MarkLazyScriptRoot(trc, (LazyScript **)addr, "exact-lazy-script"); break;
       case THING_ROOT_SHAPE:       MarkShapeRoot(trc, (Shape **)addr, "exact-shape"); break;
       case THING_ROOT_BASE_SHAPE:  MarkBaseShapeRoot(trc, (BaseShape **)addr, "exact-baseshape"); break;
       case THING_ROOT_TYPE:        MarkTypeRoot(trc, (types::Type *)addr, "exact-type"); break;
       case THING_ROOT_TYPE_OBJECT: MarkTypeObjectRoot(trc, (types::TypeObject **)addr, "exact-typeobject"); break;
       case THING_ROOT_JIT_CODE:    MarkJitCodeRoot(trc, (jit::JitCode **)addr, "exact-jitcode"); break;
       case THING_ROOT_VALUE:       MarkValueRoot(trc, (Value *)addr, "exact-value"); break;
       case THING_ROOT_ID:          MarkIdRoot(trc, (jsid *)addr, "exact-id"); break;
       case THING_ROOT_BINDINGS:    ((Bindings *)addr)->trace(trc); break;
       case THING_ROOT_PROPERTY_DESCRIPTOR: ((JSPropertyDescriptor *)addr)->trace(trc); break;
       case THING_ROOT_CUSTOM: {
           // 'rooter' is a member within a class containing a vtable. Back up
           // to the vtable and call trace() through it.
           const size_t rooterOffset = offsetof(RootedGeneric<void*>, rooter);
           reinterpret_cast< RootedGeneric<void*>* >(uintptr_t(rooter) - rooterOffset)->trace(trc);
           break;
       }
       default: MOZ_ASSUME_UNREACHABLE("Invalid THING_ROOT kind"); break;
     }
 }
 static inline void
 MarkExactStackRootList(JSTracer *trc, Rooted<void*> *rooter, ThingRootKind kind)
 {
     while (rooter) {
         MarkExactStackRoot(trc, rooter, kind);
         rooter = rooter->previous();
     }
 }
 static void
 MarkExactStackRoots(JSTracer *trc)
 {
     for (unsigned i = 0; i < THING_ROOT_LIMIT; i++) {
         for (ContextIter cx(trc->runtime()); !cx.done(); cx.next())
             MarkExactStackRootList(trc, cx->thingGCRooters[i], ThingRootKind(i));
         MarkExactStackRootList(trc, trc->runtime()->mainThread.thingGCRooters[i], ThingRootKind(i));
     }
 }
 #endif /* JSGC_USE_EXACT_ROOTING */
 enum ConservativeGCTest
 {
     CGCT_VALID,
     CGCT_LOWBITSET, /* excluded because one of the low bits was set */
     CGCT_NOTARENA,  /* not within arena range in a chunk */
     CGCT_OTHERCOMPARTMENT,  /* in another compartment */
     CGCT_NOTCHUNK,  /* not within a valid chunk */
     CGCT_FREEARENA, /* within arena containing only free things */
     CGCT_NOTLIVE,   /* gcthing is not allocated */
     CGCT_END
 };
 /*
  * Tests whether w is a (possibly dead) GC thing. Returns CGCT_VALID and
  * details about the thing if so. On failure, returns the reason for rejection.
  */
 static inline ConservativeGCTest
 IsAddressableGCThing(JSRuntime *rt, uintptr_t w,
                      bool skipUncollectedCompartments,
                      gc::AllocKind *thingKindPtr,
                      ArenaHeader **arenaHeader,
                      void **thing)
 {
     /*
      * We assume that the compiler never uses sub-word alignment to store
      * pointers and does not tag pointers on its own. Additionally, the value
      * representation for all values and the jsid representation for GC-things
      * do not touch the low two bits. Thus any word with the low two bits set
      * is not a valid GC-thing.
      */
     JS_STATIC_ASSERT(JSID_TYPE_STRING == 0 && JSID_TYPE_OBJECT == 4);
     if (w & 0x3)
         return CGCT_LOWBITSET;
     /*
      * An object jsid has its low bits tagged. In the value representation on
      * 64-bit, the high bits are tagged.
      */
     const uintptr_t JSID_PAYLOAD_MASK = ~uintptr_t(JSID_TYPE_MASK);
 #if JS_BITS_PER_WORD == 32
     uintptr_t addr = w & JSID_PAYLOAD_MASK;
 #elif JS_BITS_PER_WORD == 64
     uintptr_t addr = w & JSID_PAYLOAD_MASK & JSVAL_PAYLOAD_MASK;
 #endif
     Chunk *chunk = Chunk::fromAddress(addr);
     if (!rt->gcChunkSet.has(chunk))
         return CGCT_NOTCHUNK;
     /*
      * We query for pointers outside the arena array after checking for an
      * allocated chunk. Such pointers are rare and we want to reject them
      * after doing more likely rejections.
      */
     if (!Chunk::withinArenasRange(addr))
         return CGCT_NOTARENA;
     /* If the arena is not currently allocated, don't access the header. */
     size_t arenaOffset = Chunk::arenaIndex(addr);
     if (chunk->decommittedArenas.get(arenaOffset))
         return CGCT_FREEARENA;
     ArenaHeader *aheader = &chunk->arenas[arenaOffset].aheader;
     if (!aheader->allocated())
         return CGCT_FREEARENA;
     if (skipUncollectedCompartments && !aheader->zone->isCollecting())
         return CGCT_OTHERCOMPARTMENT;
     AllocKind thingKind = aheader->getAllocKind();
     uintptr_t offset = addr & ArenaMask;
     uintptr_t minOffset = Arena::firstThingOffset(thingKind);
     if (offset < minOffset)
         return CGCT_NOTARENA;
     /* addr can point inside the thing so we must align the address. */
     uintptr_t shift = (offset - minOffset) % Arena::thingSize(thingKind);
     addr -= shift;
     if (thing)
         *thing = reinterpret_cast<void *>(addr);
     if (arenaHeader)
         *arenaHeader = aheader;
     if (thingKindPtr)
         *thingKindPtr = thingKind;
     return CGCT_VALID;
 }
 /*
  * Returns CGCT_VALID and mark it if the w can be a  live GC thing and sets
  * thingKind accordingly. Otherwise returns the reason for rejection.
  */
 static inline ConservativeGCTest
 MarkIfGCThingWord(JSTracer *trc, uintptr_t w)
 {
     void *thing;
     ArenaHeader *aheader;
     AllocKind thingKind;
     ConservativeGCTest status =
         IsAddressableGCThing(trc->runtime(), w, IS_GC_MARKING_TRACER(trc),
                              &thingKind, &aheader, &thing);
     if (status != CGCT_VALID)
         return status;
     /*
      * Check if the thing is free. We must use the list of free spans as at
      * this point we no longer have the mark bits from the previous GC run and
      * we must account for newly allocated things.
      */
     if (InFreeList(aheader, thing))
         return CGCT_NOTLIVE;
     JSGCTraceKind traceKind = MapAllocToTraceKind(thingKind);
 #ifdef DEBUG
     const char pattern[] = "machine_stack %p";
     char nameBuf[sizeof(pattern) - 2 + sizeof(thing) * 2];
     JS_snprintf(nameBuf, sizeof(nameBuf), pattern, thing);
     trc->setTracingName(nameBuf);
 #endif
     trc->setTracingLocation((void *)w);
     void *tmp = thing;
     MarkKind(trc, &tmp, traceKind);
     JS_ASSERT(tmp == thing);
 #ifdef DEBUG
     if (trc->runtime()->gcIncrementalState == MARK_ROOTS)
         trc->runtime()->mainThread.gcSavedRoots.append(
             PerThreadData::SavedGCRoot(thing, traceKind));
 #endif
     return CGCT_VALID;
 }
 #ifndef JSGC_USE_EXACT_ROOTING
 static void
 MarkWordConservatively(JSTracer *trc, uintptr_t w)
 {
     /*
      * The conservative scanner may access words that valgrind considers as
      * undefined. To avoid false positives and not to alter valgrind view of
      * the memory we make as memcheck-defined the argument, a copy of the
      * original word. See bug 572678.
      */
 #ifdef MOZ_VALGRIND
     JS_SILENCE_UNUSED_VALUE_IN_EXPR(VALGRIND_MAKE_MEM_DEFINED(&w, sizeof(w)));
 #endif
     MarkIfGCThingWord(trc, w);
 }
 MOZ_ASAN_BLACKLIST
 static void
 MarkRangeConservatively(JSTracer *trc, const uintptr_t *begin, const uintptr_t *end)
 {
     JS_ASSERT(begin <= end);
     for (const uintptr_t *i = begin; i < end; ++i)
         MarkWordConservatively(trc, *i);
 }
 static void
 MarkRangeConservativelyAndSkipIon(JSTracer *trc, JSRuntime *rt, const uintptr_t *begin, const uintptr_t *end)
 {
     const uintptr_t *i = begin;
 #if JS_STACK_GROWTH_DIRECTION < 0 && defined(JS_ION) && !defined(JS_ARM_SIMULATOR)
     // Walk only regions in between JIT activations. Note that non-volatile
     // registers are spilled to the stack before the entry frame, ensuring
     // that the conservative scanner will still see them.
     //
     // If the ARM simulator is enabled, JIT activations are not on the native
     // stack but on the simulator stack, so we don't have to skip JIT regions
     // in this case.
     for (jit::JitActivationIterator iter(rt); !iter.done(); ++iter) {
         uintptr_t *jitMin, *jitEnd;
         iter.jitStackRange(jitMin, jitEnd);
         MarkRangeConservatively(trc, i, jitMin);
         i = jitEnd;
     }
 #endif
     // Mark everything after the most recent Ion activation.
     MarkRangeConservatively(trc, i, end);
 }
 static MOZ_NEVER_INLINE void
 MarkConservativeStackRoots(JSTracer *trc, bool useSavedRoots)
 {
     JSRuntime *rt = trc->runtime();
 #ifdef DEBUG
     if (useSavedRoots) {
         for (PerThreadData::SavedGCRoot *root = rt->mainThread.gcSavedRoots.begin();
              root != rt->mainThread.gcSavedRoots.end();
              root++)
         {
             trc->setTracingName("cstack");
             MarkKind(trc, &root->thing, root->kind);
         }
         return;
     }
     if (rt->gcIncrementalState == MARK_ROOTS)
         rt->mainThread.gcSavedRoots.clearAndFree();
 #endif
     ConservativeGCData *cgcd = &rt->conservativeGC;
     if (!cgcd->hasStackToScan()) {
 #ifdef JS_THREADSAFE
         JS_ASSERT(!rt->requestDepth);
 #endif
         return;
     }
     uintptr_t *stackMin, *stackEnd;
 #if JS_STACK_GROWTH_DIRECTION > 0
     stackMin = reinterpret_cast<uintptr_t *>(rt->nativeStackBase);
     stackEnd = cgcd->nativeStackTop;
 #else
     stackMin = cgcd->nativeStackTop + 1;
     stackEnd = reinterpret_cast<uintptr_t *>(rt->nativeStackBase);
 #endif
     JS_ASSERT(stackMin <= stackEnd);
     MarkRangeConservativelyAndSkipIon(trc, rt, stackMin, stackEnd);
     MarkRangeConservatively(trc, cgcd->registerSnapshot.words,
                             ArrayEnd(cgcd->registerSnapshot.words));
 }
 void
 js::MarkStackRangeConservatively(JSTracer *trc, Value *beginv, Value *endv)
 {
     const uintptr_t *begin = beginv->payloadUIntPtr();
     const uintptr_t *end = endv->payloadUIntPtr();
 #ifdef JS_NUNBOX32
     /*
      * With 64-bit jsvals on 32-bit systems, we can optimize a bit by
      * scanning only the payloads.
      */
     JS_ASSERT(begin <= end);
     for (const uintptr_t *i = begin; i < end; i += sizeof(Value) / sizeof(uintptr_t))
         MarkWordConservatively(trc, *i);
 #else
     MarkRangeConservatively(trc, begin, end);
 #endif
 }
 #endif /* JSGC_USE_EXACT_ROOTING */
 MOZ_NEVER_INLINE void
 ConservativeGCData::recordStackTop()
 {
     /* Update the native stack pointer if it points to a bigger stack. */
     uintptr_t dummy;
     nativeStackTop = &dummy;
     /*
      * To record and update the register snapshot for the conservative scanning
      * with the latest values we use setjmp.
      */
 #if defined(_MSC_VER)
 # pragma warning(push)
 # pragma warning(disable: 4611)
 #endif
     (void) setjmp(registerSnapshot.jmpbuf);
 #if defined(_MSC_VER)
 # pragma warning(pop)
 #endif
 }
 void
 JS::AutoIdArray::trace(JSTracer *trc)
 {
     JS_ASSERT(tag_ == IDARRAY);
     gc::MarkIdRange(trc, idArray->length, idArray->vector, "JSAutoIdArray.idArray");
 }
 inline void
 AutoGCRooter::trace(JSTracer *trc)
 {
     switch (tag_) {
       case PARSER:
         frontend::MarkParser(trc, this);
         return;
       case IDARRAY: {
         JSIdArray *ida = static_cast<AutoIdArray *>(this)->idArray;
         MarkIdRange(trc, ida->length, ida->vector, "JS::AutoIdArray.idArray");
         return;
       }
       case DESCRIPTORS: {
         PropDescArray &descriptors =
             static_cast<AutoPropDescArrayRooter *>(this)->descriptors;
         for (size_t i = 0, len = descriptors.length(); i < len; i++) {
             PropDesc &desc = descriptors[i];
             MarkValueRoot(trc, &desc.pd_, "PropDesc::pd_");
             MarkValueRoot(trc, &desc.value_, "PropDesc::value_");
             MarkValueRoot(trc, &desc.get_, "PropDesc::get_");
             MarkValueRoot(trc, &desc.set_, "PropDesc::set_");
         }
         return;
       }
       case ID:
         MarkIdRoot(trc, &static_cast<AutoIdRooter *>(this)->id_, "JS::AutoIdRooter.id_");
         return;
       case VALVECTOR: {
         AutoValueVector::VectorImpl &vector = static_cast<AutoValueVector *>(this)->vector;
         MarkValueRootRange(trc, vector.length(), vector.begin(), "js::AutoValueVector.vector");
         return;
       }
       case IDVECTOR: {
         AutoIdVector::VectorImpl &vector = static_cast<AutoIdVector *>(this)->vector;
         MarkIdRootRange(trc, vector.length(), vector.begin(), "js::AutoIdVector.vector");
         return;
       }
       case SHAPEVECTOR: {
         AutoShapeVector::VectorImpl &vector = static_cast<js::AutoShapeVector *>(this)->vector;
         MarkShapeRootRange(trc, vector.length(), const_cast<Shape **>(vector.begin()),
                            "js::AutoShapeVector.vector");
         return;
       }
       case OBJVECTOR: {
         AutoObjectVector::VectorImpl &vector = static_cast<AutoObjectVector *>(this)->vector;
         MarkObjectRootRange(trc, vector.length(), vector.begin(), "js::AutoObjectVector.vector");
         return;
       }
       case FUNVECTOR: {
         AutoFunctionVector::VectorImpl &vector = static_cast<AutoFunctionVector *>(this)->vector;
         MarkObjectRootRange(trc, vector.length(), vector.begin(), "js::AutoFunctionVector.vector");
         return;
       }
       case STRINGVECTOR: {
         AutoStringVector::VectorImpl &vector = static_cast<AutoStringVector *>(this)->vector;
         MarkStringRootRange(trc, vector.length(), vector.begin(), "js::AutoStringVector.vector");
         return;
       }
       case NAMEVECTOR: {
         AutoNameVector::VectorImpl &vector = static_cast<AutoNameVector *>(this)->vector;
         MarkStringRootRange(trc, vector.length(), vector.begin(), "js::AutoNameVector.vector");
         return;
       }
       case VALARRAY: {
         /*
          * We don't know the template size parameter, but we can safely treat it
          * as an AutoValueArray<1> because the length is stored separately.
          */
         AutoValueArray<1> *array = static_cast<AutoValueArray<1> *>(this);
         MarkValueRootRange(trc, array->length(), array->begin(), "js::AutoValueArray");
         return;
       }
       case SCRIPTVECTOR: {
         AutoScriptVector::VectorImpl &vector = static_cast<AutoScriptVector *>(this)->vector;
         MarkScriptRootRange(trc, vector.length(), vector.begin(), "js::AutoScriptVector.vector");
         return;
       }
       case OBJOBJHASHMAP: {
         AutoObjectObjectHashMap::HashMapImpl &map = static_cast<AutoObjectObjectHashMap *>(this)->map;
         for (AutoObjectObjectHashMap::Enum e(map); !e.empty(); e.popFront()) {
             MarkObjectRoot(trc, &e.front().value(), "AutoObjectObjectHashMap value");
             trc->setTracingLocation((void *)&e.front().key());
             JSObject *key = e.front().key();
             MarkObjectRoot(trc, &key, "AutoObjectObjectHashMap key");
             if (key != e.front().key())
                 e.rekeyFront(key);
         }
         return;
       }
       case OBJU32HASHMAP: {
         AutoObjectUnsigned32HashMap *self = static_cast<AutoObjectUnsigned32HashMap *>(this);
         AutoObjectUnsigned32HashMap::HashMapImpl &map = self->map;
         for (AutoObjectUnsigned32HashMap::Enum e(map); !e.empty(); e.popFront()) {
             JSObject *key = e.front().key();
             MarkObjectRoot(trc, &key, "AutoObjectUnsignedHashMap key");
             if (key != e.front().key())
                 e.rekeyFront(key);
         }
         return;
       }
       case OBJHASHSET: {
         AutoObjectHashSet *self = static_cast<AutoObjectHashSet *>(this);
         AutoObjectHashSet::HashSetImpl &set = self->set;
         for (AutoObjectHashSet::Enum e(set); !e.empty(); e.popFront()) {
             JSObject *obj = e.front();
             MarkObjectRoot(trc, &obj, "AutoObjectHashSet value");
             if (obj != e.front())
                 e.rekeyFront(obj);
         }
         return;
       }
       case HASHABLEVALUE: {
         AutoHashableValueRooter *rooter = static_cast<AutoHashableValueRooter *>(this);
         rooter->trace(trc);
         return;
       }
       case IONMASM: {
 #ifdef JS_ION
         static_cast<js::jit::MacroAssembler::AutoRooter *>(this)->masm()->trace(trc);
 #endif
         return;
       }
       case IONALLOC: {
 #ifdef JS_ION
         static_cast<js::jit::AutoTempAllocatorRooter *>(this)->trace(trc);
 #endif
         return;
       }
       case WRAPPER: {
         /*
          * We need to use MarkValueUnbarriered here because we mark wrapper
          * roots in every slice. This is because of some rule-breaking in
          * RemapAllWrappersForObject; see comment there.
          */
           MarkValueUnbarriered(trc, &static_cast<AutoWrapperRooter *>(this)->value.get(),
                                "JS::AutoWrapperRooter.value");
         return;
       }
       case WRAPVECTOR: {
         AutoWrapperVector::VectorImpl &vector = static_cast<AutoWrapperVector *>(this)->vector;
         /*
          * We need to use MarkValueUnbarriered here because we mark wrapper
          * roots in every slice. This is because of some rule-breaking in
          * RemapAllWrappersForObject; see comment there.
          */
         for (WrapperValue *p = vector.begin(); p < vector.end(); p++)
             MarkValueUnbarriered(trc, &p->get(), "js::AutoWrapperVector.vector");
         return;
       }
       case JSONPARSER:
         static_cast<js::JSONParser *>(this)->trace(trc);
         return;
       case CUSTOM:
         static_cast<JS::CustomAutoRooter *>(this)->trace(trc);
         return;
     }
     JS_ASSERT(tag_ >= 0);
     if (Value *vp = static_cast<AutoArrayRooter *>(this)->array)
         MarkValueRootRange(trc, tag_, vp, "JS::AutoArrayRooter.array");
 }
 /* static */ void
 AutoGCRooter::traceAll(JSTracer *trc)
 {
     for (ContextIter cx(trc->runtime()); !cx.done(); cx.next()) {
         for (js::AutoGCRooter *gcr = cx->autoGCRooters; gcr; gcr = gcr->down)
             gcr->trace(trc);
     }
 }
 /* static */ void
 AutoGCRooter::traceAllWrappers(JSTracer *trc)
 {
     for (ContextIter cx(trc->runtime()); !cx.done(); cx.next()) {
         for (js::AutoGCRooter *gcr = cx->autoGCRooters; gcr; gcr = gcr->down) {
             if (gcr->tag_ == WRAPVECTOR || gcr->tag_ == WRAPPER)
                 gcr->trace(trc);
         }
     }
 }
 void
 AutoHashableValueRooter::trace(JSTracer *trc)
 {
     MarkValueRoot(trc, reinterpret_cast<Value*>(&value), "AutoHashableValueRooter");
 }
 void
 StackShape::trace(JSTracer *trc)
 {
     if (base)
         MarkBaseShapeRoot(trc, (BaseShape**) &base, "StackShape base");
     MarkIdRoot(trc, (jsid*) &propid, "StackShape id");
 }
 void
 JSPropertyDescriptor::trace(JSTracer *trc)
 {
     if (obj)
         MarkObjectRoot(trc, &obj, "Descriptor::obj");
     MarkValueRoot(trc, &value, "Descriptor::value");
     if ((attrs & JSPROP_GETTER) && getter) {
         JSObject *tmp = JS_FUNC_TO_DATA_PTR(JSObject *, getter);
         MarkObjectRoot(trc, &tmp, "Descriptor::get");
         getter = JS_DATA_TO_FUNC_PTR(JSPropertyOp, tmp);
     }
     if ((attrs & JSPROP_SETTER) && setter) {
         JSObject *tmp = JS_FUNC_TO_DATA_PTR(JSObject *, setter);
         MarkObjectRoot(trc, &tmp, "Descriptor::set");
         setter = JS_DATA_TO_FUNC_PTR(JSStrictPropertyOp, tmp);
     }
 }
 namespace js {
 namespace gc {
 template<typename T>
 struct PersistentRootedMarker
 {
     typedef PersistentRooted<T> Element;
     typedef mozilla::LinkedList<Element> List;
     typedef void (*MarkFunc)(JSTracer *trc, T *ref, const char *name);
     template <MarkFunc Mark>
     static void
     markChainIfNotNull(JSTracer *trc, List &list, const char *name)
     {
         for (Element *r = list.getFirst(); r; r = r->getNext()) {
             if (r->get())
                 Mark(trc, r->address(), name);
         }
     }
     template <MarkFunc Mark>
     static void
     markChain(JSTracer *trc, List &list, const char *name)
     {
         for (Element *r = list.getFirst(); r; r = r->getNext())
             Mark(trc, r->address(), name);
     }
 };
 }
 }
 void
 js::gc::MarkPersistentRootedChains(JSTracer *trc)
 {
     JSRuntime *rt = trc->runtime();
     // Mark the PersistentRooted chains of types that may be null.
     PersistentRootedMarker<JSFunction*>::markChainIfNotNull<MarkObjectRoot>(
         trc, rt->functionPersistentRooteds, "PersistentRooted<JSFunction *>");
     PersistentRootedMarker<JSObject*>::markChainIfNotNull<MarkObjectRoot>(
         trc, rt->objectPersistentRooteds, "PersistentRooted<JSObject *>");
     PersistentRootedMarker<JSScript*>::markChainIfNotNull<MarkScriptRoot>(
         trc, rt->scriptPersistentRooteds, "PersistentRooted<JSScript *>");
     PersistentRootedMarker<JSString*>::markChainIfNotNull<MarkStringRoot>(
         trc, rt->stringPersistentRooteds, "PersistentRooted<JSString *>");
     // Mark the PersistentRooted chains of types that are never null.
     PersistentRootedMarker<jsid>::markChain<MarkIdRoot>(trc, rt->idPersistentRooteds,
                                                         "PersistentRooted<jsid>");
     PersistentRootedMarker<Value>::markChain<MarkValueRoot>(trc, rt->valuePersistentRooteds,
                                                             "PersistentRooted<Value>");
 }
 void
 js::gc::MarkRuntime(JSTracer *trc, bool useSavedRoots)
 {
     JSRuntime *rt = trc->runtime();
     JS_ASSERT(trc->callback != GCMarker::GrayCallback);
     JS_ASSERT(!rt->mainThread.suppressGC);
     if (IS_GC_MARKING_TRACER(trc)) {
         for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) {
             if (!c->zone()->isCollecting())
                 c->markCrossCompartmentWrappers(trc);
         }
         Debugger::markCrossCompartmentDebuggerObjectReferents(trc);
     }
     AutoGCRooter::traceAll(trc);
     if (!rt->isBeingDestroyed()) {
 #ifdef JSGC_USE_EXACT_ROOTING
         MarkExactStackRoots(trc);
 #else
         MarkConservativeStackRoots(trc, useSavedRoots);
 #endif
         rt->markSelfHostingGlobal(trc);
     }
     for (RootRange r = rt->gcRootsHash.all(); !r.empty(); r.popFront()) {
         const RootEntry &entry = r.front();
         const char *name = entry.value().name ? entry.value().name : "root";
         JSGCRootType type = entry.value().type;
         void *key = entry.key();
         if (type == JS_GC_ROOT_VALUE_PTR) {
             MarkValueRoot(trc, reinterpret_cast<Value *>(key), name);
         } else if (*reinterpret_cast<void **>(key)){
             if (type == JS_GC_ROOT_STRING_PTR)
                 MarkStringRoot(trc, reinterpret_cast<JSString **>(key), name);
             else if (type == JS_GC_ROOT_OBJECT_PTR)
                 MarkObjectRoot(trc, reinterpret_cast<JSObject **>(key), name);
             else if (type == JS_GC_ROOT_SCRIPT_PTR)
                 MarkScriptRoot(trc, reinterpret_cast<JSScript **>(key), name);
             else
                 MOZ_ASSUME_UNREACHABLE("unexpected js::RootInfo::type value");
         }
     }
     MarkPersistentRootedChains(trc);
     if (rt->scriptAndCountsVector) {
         ScriptAndCountsVector &vec = *rt->scriptAndCountsVector;
         for (size_t i = 0; i < vec.length(); i++)
             MarkScriptRoot(trc, &vec[i].script, "scriptAndCountsVector");
     }
     if (!rt->isBeingDestroyed() && !trc->runtime()->isHeapMinorCollecting()) {
         if (!IS_GC_MARKING_TRACER(trc) || rt->atomsCompartment()->zone()->isCollecting()) {
             MarkPermanentAtoms(trc);
             MarkAtoms(trc);
 #ifdef JS_ION
             jit::JitRuntime::Mark(trc);
 #endif
         }
     }
     for (ContextIter acx(rt); !acx.done(); acx.next())
         acx->mark(trc);
     for (ZonesIter zone(rt, SkipAtoms); !zone.done(); zone.next()) {
         if (IS_GC_MARKING_TRACER(trc) && !zone->isCollecting())
             continue;
         /* Do not discard scripts with counts while profiling. */
         if (rt->profilingScripts && !rt->isHeapMinorCollecting()) {
             for (CellIterUnderGC i(zone, FINALIZE_SCRIPT); !i.done(); i.next()) {
                 JSScript *script = i.get<JSScript>();
                 if (script->hasScriptCounts()) {
                     MarkScriptRoot(trc, &script, "profilingScripts");
                     JS_ASSERT(script == i.get<JSScript>());
                 }
             }
         }
     }
     /* We can't use GCCompartmentsIter if we're called from TraceRuntime. */
     for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next()) {
         if (trc->runtime()->isHeapMinorCollecting())
             c->globalWriteBarriered = false;
         if (IS_GC_MARKING_TRACER(trc) && !c->zone()->isCollecting())
             continue;
         /* During a GC, these are treated as weak pointers. */
         if (!IS_GC_MARKING_TRACER(trc)) {
             if (c->watchpointMap)
                 c->watchpointMap->markAll(trc);
         }
         /* Mark debug scopes, if present */
         if (c->debugScopes)
             c->debugScopes->mark(trc);
     }
     MarkInterpreterActivations(rt, trc);
 #ifdef JS_ION
     jit::MarkJitActivations(rt, trc);
 #endif
     if (!rt->isHeapMinorCollecting()) {
         /*
          * All JSCompartment::mark does is mark the globals for compartments
          * which have been entered. Globals aren't nursery allocated so there's
          * no need to do this for minor GCs.
          */
         for (CompartmentsIter c(rt, SkipAtoms); !c.done(); c.next())
             c->markRoots(trc);
         /*
          * The embedding can register additional roots here.
          *
          * We don't need to trace these in a minor GC because all pointers into
          * the nursery should be in the store buffer, and we want to avoid the
          * time taken to trace all these roots.
          */
         for (size_t i = 0; i < rt->gcBlackRootTracers.length(); i++) {
             const JSRuntime::ExtraTracer &e = rt->gcBlackRootTracers[i];
             (*e.op)(trc, e.data);
         }
         /* During GC, we don't mark gray roots at this stage. */
         if (JSTraceDataOp op = rt->gcGrayRootTracer.op) {
             if (!IS_GC_MARKING_TRACER(trc))
                 (*op)(trc, rt->gcGrayRootTracer.data);
         }
     }
 }
 void
 js::gc::BufferGrayRoots(GCMarker *gcmarker)
 {
     JSRuntime *rt = gcmarker->runtime();
     gcmarker->startBufferingGrayRoots();
     if (JSTraceDataOp op = rt->gcGrayRootTracer.op)
         (*op)(gcmarker, rt->gcGrayRootTracer.data);
     gcmarker->endBufferingGrayRoots();
 }

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js/src/gc/RootMarking.cpp@6474c204b198 (annotated)

js/src/gc/RootMarking.cpp