Fix bug with guarded fields and deserialization.

runtime/vm/snapshot.cc

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/snapshot.h"
 
 #include "platform/assert.h"
 #include "vm/bigint_operations.h"
 #include "vm/bootstrap.h"
 #include "vm/class_finalizer.h"
@@ skipping 132 matching lines @@
 
 SnapshotReader::SnapshotReader(const uint8_t* buffer,
                                intptr_t size,
                                Snapshot::Kind kind,
                                Isolate* isolate)
     : BaseReader(buffer, size),
       kind_(kind),
       isolate_(isolate),
       cls_(Class::Handle()),
       obj_(Object::Handle()),
+      array_(Array::Handle()),
+      field_(Field::Handle()),
       str_(String::Handle()),
       library_(Library::Handle()),
       type_(AbstractType::Handle()),
       type_arguments_(AbstractTypeArguments::Handle()),
       tokens_(Array::Handle()),
       stream_(TokenStream::Handle()),
       data_(ExternalTypedData::Handle()),
       error_(UnhandledException::Handle()),
       backward_references_((kind == Snapshot::kFull) ?
                            kNumInitialReferencesInFullSnapshot :
@@ skipping 619 matching lines @@
         *result ^= Object::Allocate(cls_.id(),
                                     instance_size,
                                     HEAP_SPACE(kind_));
       }
     } else {
       cls_ ^= ReadObjectImpl();
       ASSERT(!cls_.IsNull());
       instance_size = cls_.instance_size();
     }
     intptr_t offset = Object::InstanceSize();
+    intptr_t result_cid = result->GetClassId();
     while (offset < instance_size) {
       obj_ = ReadObjectRef();
       result->SetFieldAtOffset(offset, obj_);
+      if (kind_ == Snapshot::kMessage) {
+        cls_ = isolate()->class_table()->At(result_cid);

[Ivan Posva, 2013/11/01 04:50:05]

You want to look this up only once and not for every field in the object, but I
also understand that you cannot share the handle in that case. Would be OK to
add a TODO and investigate this with Siva after having addressed the crash fix.

[Florian Schneider, 2013/11/01 10:39:27]

Done. Added TODO.

+        array_ = cls_.OffsetToFieldMap();

[Ivan Posva, 2013/11/01 04:50:05]

ditto

[Florian Schneider, 2013/11/01 10:39:27]

Done.

+        field_ ^= array_.At(offset / kWordSize);

[Ivan Posva, 2013/11/01 04:50:05]

offset >> kWordSizeLog2

[Florian Schneider, 2013/11/01 10:39:27]

Done.

+        // Entries can be null because offset can be outside of instance fields
+        // due to rounded allocation size.
+        if (!field_.IsNull()) {
+          ASSERT(field_.Offset() == offset);
+          field_.UpdateGuardedCidAndLength(obj_);
+        }
+      }

[Ivan Posva, 2013/11/01 04:50:05]

We also wanted to assert that when deserializing other snapshots these values
were correct. At least add a TODO.

[Florian Schneider, 2013/11/01 10:39:27]

Added TODO. I'll think about how to assert this for the other kinds.

       offset += kWordSize;
     }
     if (kind_ == Snapshot::kFull) {
       result->SetCreatedFromSnapshot();
     } else if (result->IsCanonical()) {
       *result = result->CheckAndCanonicalize(NULL);
       ASSERT(!result->IsNull());
     }
     return result->raw();
   }
@@ skipping 681 matching lines @@
     UnmarkAll();
     isolate->set_long_jump_base(base);
   } else {
     isolate->set_long_jump_base(base);
     ThrowException(exception_type(), exception_msg());
   }
 }
 
 
 }  // namespace dart