- Create an all static TypedDataView class which uses implicit field offset

runtime/vm/class_finalizer.cc

 // Copyright (c) 2013, 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/class_finalizer.h"
 
 #include "vm/flags.h"
 #include "vm/heap.h"
 #include "vm/isolate.h"
 #include "vm/longjump.h"
@@ skipping 149 matching lines @@
     // Clear pending classes array.
     class_array = GrowableObjectArray::New();
     object_store->set_pending_classes(class_array);
   } else {
     retval = false;
   }
   isolate->set_long_jump_base(base);
   if (FLAG_use_cha) {
     RemoveOptimizedCode(added_subclasses_to_cids);
   }
+  VerifyImplicitFieldOffsets();

[regis, 2013/04/09 20:27:39]

I am getting a crash here in the case class finalization reported an error.
Moving this call just after line 162 solves the problem, but is that correct?
Is the system in an inconsistent state after an error is reported?
You can reproduce by generating the snapshot with the flag
--error_on_malformed_type at r21166, because there is an error in the core lib.

[siva, 2013/04/09 21:30:29]

I guess in your case a type error occurred before the classes in dart:typeddata
got finalized, as a result of the error the field offsets are not set for the
typeddata classes and this assertion fails.

We could move the code to the successful case as you indicate, what about the
other pieces like RemoveOptimizedCode etc. should that be run only of there are
no errors?

Another option might be to do the verification only if the dart:typedata classes
are marked as being 'finalized'. 

On 2013/04/09 20:27:39, regis wrote:

   return retval;
 }
 
 
 // Adds all interfaces of cls into 'collected'. Duplicate entries may occur.
 // No cycles are allowed.
 void ClassFinalizer::CollectInterfaces(const Class& cls,
                                        const GrowableObjectArray& collected) {
   const Array& interface_array = Array::Handle(cls.interfaces());
   AbstractType& interface = AbstractType::Handle();
@@ skipping 1786 matching lines @@
 
 void ClassFinalizer::ReportError(const char* format, ...) {
   va_list args;
   va_start(args, format);
   const Error& error = Error::Handle(
       Parser::FormatError(Script::Handle(), -1, "Error", format, args));
   va_end(args);
   ReportError(error);
 }
 
+
+void ClassFinalizer::VerifyImplicitFieldOffsets() {
+#ifdef DEBUG
+  const ClassTable& class_table = *(Isolate::Current()->class_table());
+  Class& cls = Class::Handle();
+  Array& fields_array = Array::Handle();
+  Field& field = Field::Handle();
+  String& name = String::Handle();
+  String& expected_name = String::Handle();
+
+  // First verify field offsets of all the TypedDataView classes.
+  for (intptr_t cid = kTypedDataInt8ArrayViewCid;
+       cid <= kTypedDataFloat32x4ArrayViewCid;
+       cid++) {
+    cls = class_table.At(cid);  // Get the TypedDataView class.
+    cls = cls.SuperClass();  // Get it's super class '_TypedListView'.
+    fields_array ^= cls.fields();
+    ASSERT(fields_array.Length() == TypedDataView::NumberOfFields());
+    field ^= fields_array.At(0);
+    ASSERT(field.Offset() == TypedDataView::data_offset());
+    name ^= field.name();
+    expected_name ^= String::New("_typeddata");
+    ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
+    field ^= fields_array.At(1);
+    ASSERT(field.Offset() == TypedDataView::offset_in_bytes_offset());
+    name ^= field.name();
+    ASSERT(name.Equals("offsetInBytes"));
+    field ^= fields_array.At(2);
+    ASSERT(field.Offset() == TypedDataView::length_offset());
+    name ^= field.name();
+    ASSERT(name.Equals("length"));
+  }
+
+  // Now verify field offsets of '_ByteDataView' class.
+  cls = class_table.At(kByteDataViewCid);
+  fields_array ^= cls.fields();
+  ASSERT(fields_array.Length() == TypedDataView::NumberOfFields());
+  field ^= fields_array.At(0);
+  ASSERT(field.Offset() == TypedDataView::data_offset());
+  name ^= field.name();
+  expected_name ^= String::New("_typeddata");
+  ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
+  field ^= fields_array.At(1);
+  ASSERT(field.Offset() == TypedDataView::offset_in_bytes_offset());
+  name ^= field.name();
+  expected_name ^= String::New("_offset");
+  ASSERT(String::EqualsIgnoringPrivateKey(name, expected_name));
+  field ^= fields_array.At(2);
+  ASSERT(field.Offset() == TypedDataView::length_offset());
+  name ^= field.name();
+  ASSERT(name.Equals("length"));
+#endif
+}
+
 }  // namespace dart