Explicitly initialize Bigint members after uninitialized allocations.

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/exceptions.h"
@@ skipping 231 matching lines @@
   obj->ptr()->value_ = value;
   return obj;
 }
 
 
 RawBigint* SnapshotReader::NewBigint(const char* hex_string) {
   ASSERT(kind_ == Snapshot::kFull);
   ASSERT(isolate()->no_gc_scope_depth() != 0);
   cls_ = object_store()->bigint_class();
   intptr_t bigint_length = BigintOperations::ComputeChunkLength(hex_string);
-  const Bigint& result = Bigint::Handle(reinterpret_cast<RawBigint*>(
-      AllocateUninitialized(cls_, Bigint::InstanceSize(bigint_length))));
-  BigintOperations::FromHexCString(hex_string, result);
-  return result.raw();
+  RawBigint* obj = reinterpret_cast<RawBigint*>(
+      AllocateUninitialized(cls_, Bigint::InstanceSize(bigint_length)));
+  obj->ptr()->allocated_length_ = bigint_length;
+  obj->ptr()->signed_length_ = bigint_length;

[siva, 2012/04/26 04:45:04]

why not add a set_allocated_length() and set_signed_length() in object.h and use
them here

or

Bigint& result = Bigint::Handle();
{
  NoGCScope nogc;
  result = AllocateUninitialized(...);
  result.raw()->ptr()->allocated_length_ = ...
  result.raw()->ptr()->signed_length_ = ...
 }
 BigintOperations::FromHexCString(...);
 return

[cshapiro, 2012/04/26 06:34:53]

Hmm... I tried to make the code look like the rest of the code in the snapshot
reader.

The NoGCScope seemed unnecessary because of the assert on line 249 and because
the entire read is wrapped in a NoGCScope on line 130.

We have a SetLength but it does something different than one would expect.  It
is confusing to me why we have these two length values in the first place.  
Let's talk about this off-line.

[siva, 2012/04/26 17:17:44]

Agree, I didn't realize we already had a NoGCScope around the caller.

Maybe in a different CL, I will add an assertion in each of this functions so
that there is no confusion.

On 2012/04/26 06:34:53, cshapiro wrote:

+  BigintOperations::FromHexCString(hex_string, Bigint::Handle(obj));
+  return obj;
 }
 
 
 RawDouble* SnapshotReader::NewDouble(double value) {
   ASSERT(kind_ == Snapshot::kFull);
   ASSERT(isolate()->no_gc_scope_depth() != 0);
   cls_ = object_store()->double_class();
   RawDouble* obj = reinterpret_cast<RawDouble*>(
       AllocateUninitialized(cls_, Double::InstanceSize()));
   obj->ptr()->value_ = value;
@@ skipping 405 matching lines @@
 
 
 void SnapshotWriterVisitor::VisitPointers(RawObject** first, RawObject** last) {
   for (RawObject** current = first; current <= last; current++) {
     RawObject* raw_obj = *current;
     writer_->WriteObject(raw_obj);
   }
 }
 
 }  // namespace dart