Fix for 7941

runtime/vm/object.cc

Index: runtime/vm/object.cc
===================================================================
--- runtime/vm/object.cc	(revision 17155)
+++ runtime/vm/object.cc	(working copy)
@@ -515,7 +515,7 @@
 
 // Make unused space in an object whose type has been transformed safe
 // for traversing during GC.
-// The unused part of the transformed object is marked as an Array
+// The unused part of the transformed object is marked as an Int8Array
 // object or a regular Object so that it can be traversed during garbage
 // collection.
 void Object::MakeUnusedSpaceTraversable(const Object& obj,
@@ -528,18 +528,17 @@
     intptr_t leftover_size = original_size - used_size;
 
     uword addr = RawObject::ToAddr(obj.raw()) + used_size;

[Ivan Posva, 2013/01/16 21:30:06]

How about adding
ASSERT(Object::InstanceSize() + kObjectAlignment == Int8Array::InstanceSize(0));

[siva, 2013/01/16 21:43:08]

Changed code a bit as discussed offline.
ASSERT(object::InstanceSize() == Int8Array::InstanceSize(0));

On 2013/01/16 21:30:06, Ivan Posva wrote:

-    if (leftover_size >= Array::InstanceSize(0)) {
-      // As we have enough space to use an array object, update the leftover
-      // space as an Array object.
-      RawArray* raw = reinterpret_cast<RawArray*>(RawObject::FromAddr(addr));
+    if (leftover_size >= Int8Array::InstanceSize(0)) {
+      // As we have enough space to use an Int8Array object, update the
+      // leftover space as an Int8Array object.
+      RawInt8Array* raw =
+          reinterpret_cast<RawInt8Array*>(RawObject::FromAddr(addr));
       uword tags = 0;
       tags = RawObject::SizeTag::update(leftover_size, tags);
-      tags = RawObject::ClassIdTag::update(kArrayCid, tags);
+      tags = RawObject::ClassIdTag::update(kInt8ArrayCid, tags);
       raw->ptr()->tags_ = tags;
-      intptr_t leftover_len =
-          ((leftover_size - Array::InstanceSize(0)) / kWordSize);
-      ASSERT(Array::InstanceSize(leftover_len) == leftover_size);
-      raw->ptr()->tags_ = tags;
+      intptr_t leftover_len = (leftover_size - Int8Array::InstanceSize(0));
+      ASSERT(Int8Array::InstanceSize(leftover_len) == leftover_size);
       raw->ptr()->length_ = Smi::New(leftover_len);
     } else {
       // Update the leftover space as a basic object.