[snapshot] avoid aliasing for snapshot reservations.

R=ulan@chromium.org

Bug: v8:7141
Change-Id: I21b82f5c3f6a2cd5f6e525d267d6c6819b1370fb
Reviewed-on: https://chromium-review.googlesource.com/796370
Commit-Queue: Yang Guo <yangguo@chromium.org>
Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#49784}

src/snapshot/builtin-deserializer-allocator.h

@@ -69,7 +69,7 @@ class BuiltinDeserializerAllocator final {
 
   // Builtin deserialization does not bake reservations into the snapshot, hence
   // this is a nop.
-  void DecodeReservation(Vector<const SerializedData::Reservation> res) {}
+  void DecodeReservation(std::vector<SerializedData::Reservation> res) {}
 
   // These methods are used to pre-allocate builtin objects prior to
   // deserialization.

src/snapshot/code-serializer.cc

@@ -432,11 +432,13 @@ ScriptData* SerializedCodeData::GetScriptData() {
   return result;
 }
 
-Vector<const SerializedData::Reservation> SerializedCodeData::Reservations()
+std::vector<SerializedData::Reservation> SerializedCodeData::Reservations()
     const {
-  return Vector<const Reservation>(
-      reinterpret_cast<const Reservation*>(data_ + kHeaderSize),
-      GetHeaderValue(kNumReservationsOffset));
+  uint32_t size = GetHeaderValue(kNumReservationsOffset);
+  std::vector<Reservation> reservations(size);
+  memcpy(reservations.data(), data_ + kHeaderSize,
+         size * sizeof(SerializedData::Reservation));
+  return reservations;
 }
 
 Vector<const byte> SerializedCodeData::Payload() const {

src/snapshot/code-serializer.h

@@ -129,7 +129,7 @@ class SerializedCodeData : public SerializedData {
   // Return ScriptData object and relinquish ownership over it to the caller.
   ScriptData* GetScriptData();
 
-  Vector<const Reservation> Reservations() const;
+  std::vector<Reservation> Reservations() const;
   Vector<const byte> Payload() const;
 
   Vector<const uint32_t> CodeStubKeys() const;

src/snapshot/default-deserializer-allocator.cc

@@ -121,7 +121,7 @@ HeapObject* DefaultDeserializerAllocator::GetObject(AllocationSpace space,
 }
 
 void DefaultDeserializerAllocator::DecodeReservation(
-    Vector<const SerializedData::Reservation> res) {
+    std::vector<SerializedData::Reservation> res) {
   DCHECK_EQ(0, reservations_[NEW_SPACE].size());
   STATIC_ASSERT(NEW_SPACE == 0);
   int current_space = NEW_SPACE;

src/snapshot/default-deserializer-allocator.h

@@ -44,7 +44,7 @@ class DefaultDeserializerAllocator final {
   // ------- Reservation Methods -------
   // Methods related to memory reservations (prior to deserialization).
 
-  void DecodeReservation(Vector<const SerializedData::Reservation> res);
+  void DecodeReservation(std::vector<SerializedData::Reservation> res);
   bool ReserveSpace();
 
   // Atomically reserves space for the two given deserializers. Guarantees

src/snapshot/serializer-common.h

@@ -255,6 +255,7 @@ class SerializedData {
  public:
   class Reservation {
    public:
+    Reservation() : reservation_(0) {}
     explicit Reservation(uint32_t size)
         : reservation_(ChunkSizeBits::encode(size)) {}
 

src/snapshot/snapshot-common.cc

@@ -358,10 +358,12 @@ SnapshotData::SnapshotData(const Serializer<AllocatorT>* serializer) {
 template SnapshotData::SnapshotData(
     const Serializer<DefaultSerializerAllocator>* serializer);
 
-Vector<const SerializedData::Reservation> SnapshotData::Reservations() const {
-  return Vector<const Reservation>(
-      reinterpret_cast<const Reservation*>(data_ + kHeaderSize),
-      GetHeaderValue(kNumReservationsOffset));
+std::vector<SerializedData::Reservation> SnapshotData::Reservations() const {
+  uint32_t size = GetHeaderValue(kNumReservationsOffset);
+  std::vector<SerializedData::Reservation> reservations(size);
+  memcpy(reservations.data(), data_ + kHeaderSize,
+         size * sizeof(SerializedData::Reservation));
+  return reservations;
 }
 
 Vector<const byte> SnapshotData::Payload() const {

src/snapshot/snapshot.h

@@ -31,7 +31,7 @@ class SnapshotData : public SerializedData {
       : SerializedData(const_cast<byte*>(snapshot.begin()), snapshot.length()) {
   }
 
-  Vector<const Reservation> Reservations() const;
+  std::vector<Reservation> Reservations() const;
   virtual Vector<const byte> Payload() const;
 
   Vector<const byte> RawData() const {