Make VerifyMarking work in the presence of grey objects

src/heap/mark-compact.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/v8.h"
 
 #include "src/base/atomicops.h"
 #include "src/base/bits.h"
 #include "src/code-stubs.h"
 #include "src/compilation-cache.h"
@@ skipping 84 matching lines @@
   VerifyMarkingVisitor visitor(heap);
   HeapObject* object;
   Address next_object_must_be_here_or_later = bottom;
 
   for (Address current = bottom; current < top; current += kPointerSize) {
     object = HeapObject::FromAddress(current);
     if (MarkCompactCollector::IsMarked(object)) {
       CHECK(current >= next_object_must_be_here_or_later);
       object->Iterate(&visitor);
       next_object_must_be_here_or_later = current + object->Size();
+      // Take into account that a marked objected is at least two pointers in

[Hannes Payer (out of office), 2015/03/09 13:49:25]

object

+      // size. If we don't skip one word, the next word gets detected as an
+      // object as well.
+      current += kPointerSize;

[Hannes Payer (out of office), 2015/03/09 13:49:25]

Now the verifier would allow grey object in the final transitive closure. I
don't think we want that. You could add an additional parameter that forces you
to check for black and/or grey.

     }
   }
 }
 
 
 static void VerifyMarking(NewSpace* space) {
   Address end = space->top();
   NewSpacePageIterator it(space->bottom(), end);
   // The bottom position is at the start of its page. Allows us to use
   // page->area_start() as start of range on all pages.
@@ skipping 4381 matching lines @@
   SlotsBuffer* buffer = *buffer_address;
   while (buffer != NULL) {
     SlotsBuffer* next_buffer = buffer->next();
     DeallocateBuffer(buffer);
     buffer = next_buffer;
   }
   *buffer_address = NULL;
 }
 }
 }  // namespace v8::internal