Deletion barrier: Distinguish+verify field initialization in ia32 generated code.

runtime/vm/gc_sweeper.cc

 // Copyright (c) 2011, 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/gc_sweeper.h"
 
 #include "vm/freelist.h"
 #include "vm/globals.h"
 #include "vm/heap.h"
 #include "vm/lockers.h"
@@ skipping 26 matching lines @@
         if (next_obj->IsMarked()) {
           // Reached the end of the free block.
           break;
         }
         // Expand the free block by the size of this object.
         free_end += next_obj->Size();
       }
       obj_size = free_end - current;
       if (is_executable) {
         memset(reinterpret_cast<void*>(current), 0xcc, obj_size);
+      } else {
+#if defined(DEBUG)
+        memset(reinterpret_cast<void*>(current), Heap::kZapByte, obj_size);
+#endif  // DEBUG
       }
       if ((current != start) || (free_end != end)) {
         // Only add to the free list if not covering the whole page.
         if (locked) {
           freelist->FreeLocked(current, obj_size);
         } else {
           freelist->Free(current, obj_size);
         }
       }
     }
@@ skipping 13 matching lines @@
     words_to_end = (raw_obj->Size() >> kWordSizeLog2);
   }
 #ifdef DEBUG
   // String::MakeExternal and Array::MakeArray create trailing filler objects,
   // but they are always unreachable. Verify that they are not marked.
   uword current = RawObject::ToAddr(raw_obj) + raw_obj->Size();
   uword end = page->object_end();
   while (current < end) {
     RawObject* cur_obj = RawObject::FromAddr(current);
     ASSERT(!cur_obj->IsMarked());
-    current += cur_obj->Size();
+    intptr_t obj_size = cur_obj->Size();
+    memset(reinterpret_cast<void*>(current), Heap::kZapByte, obj_size);
+    current += obj_size;
   }
 #endif  // DEBUG
   return words_to_end;
 }
 
 
 class SweeperTask : public ThreadPool::Task {
  public:
   SweeperTask(Isolate* isolate,
               PageSpace* old_space,
@@ skipping 66 matching lines @@
   SweeperTask* task =
       new SweeperTask(isolate->ShallowCopy(),
                       isolate->heap()->old_space(),
                       first, last,
                       freelist);
   ThreadPool* pool = Dart::thread_pool();
   pool->Run(task);
 }
 
 }  // namespace dart