Make sure Bigint._digits is always a Uint32List (instead of sometimes null).

runtime/vm/object.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/object.h"
 
 #include "include/dart_api.h"
 #include "platform/assert.h"
 #include "vm/assembler.h"
 #include "vm/cpu.h"
@@ skipping 16246 matching lines @@
   StorePointer(&raw_ptr()->neg_, value.raw());
 }
 
 
 void Bigint::set_used(const Smi& value) const {
   raw_ptr()->used_ = value.raw();
 }
 
 
 void Bigint::set_digits(const TypedData& value) const {
+  // The VM expects digits_ to be a Uint32List (not null).
+  ASSERT(!value.IsNull() && (value.GetClassId() == kTypedDataUint32ArrayCid));
   StorePointer(&raw_ptr()->digits_, value.raw());
 }
 
 
 bool Bigint::Neg() const {
   return Bool::Handle(neg()).value();
 }
 
 
 void Bigint::SetNeg(bool value) const {
@@ skipping 57 matching lines @@
   // Bool field neg should always be canonical.
   ASSERT(Bool::Handle(neg()).IsCanonical());
   // Smi field used is canonical by definition.
   if (Used() > 0) {
     // Canonicalize TypedData field digits.
     TypedData& digits_ = TypedData::Handle(digits());
     digits_ ^= digits_.CheckAndCanonicalize(NULL);
     ASSERT(!digits_.IsNull());
     set_digits(digits_);
   } else {
-    ASSERT(digits() == TypedData::null());
+    ASSERT(digits() == TypedData::EmptyUint32Array(Isolate::Current()));
   }
   return true;
 }
 
 
 RawBigint* Bigint::New(Heap::Space space) {
-  ASSERT(Isolate::Current()->object_store()->bigint_class() != Class::null());
-  Bigint& result = Bigint::Handle();
+  Isolate* isolate = Isolate::Current();
+  ASSERT(isolate->object_store()->bigint_class() != Class::null());
+  Bigint& result = Bigint::Handle(isolate);
   {
     RawObject* raw = Object::Allocate(Bigint::kClassId,
                                       Bigint::InstanceSize(),
                                       space);
     NoGCScope no_gc;
     result ^= raw;
   }
   result.set_neg(Bool::Get(false));
-  result.set_used(Smi::Handle(Smi::New(0)));
+  result.set_used(Smi::Handle(isolate, Smi::New(0)));
+  result.set_digits(
+      TypedData::Handle(isolate, TypedData::EmptyUint32Array(isolate)));
   return result.raw();
 }
 
 
 RawBigint* Bigint::NewFromInt64(int64_t value, Heap::Space space) {
   const Bigint& result = Bigint::Handle(New(space));
   result.EnsureLength(2, space);
   result.SetUsed(2);
   if (value < 0) {
     result.SetNeg(true);
@@ skipping 44 matching lines @@
       (bit_shift == 0) ? 0
                        : static_cast<uint32_t>(abs_value >> (64 - bit_shift)));
   result.Clamp();
   return result.raw();
 }
 
 
 void Bigint::EnsureLength(intptr_t length, Heap::Space space) const {
   ASSERT(length >= 0);
   TypedData& old_digits = TypedData::Handle(digits());
-  if ((length > 0) && (old_digits.IsNull() || (length > old_digits.Length()))) {
+  if ((length > 0) && (length > old_digits.Length())) {
     TypedData& new_digits = TypedData::Handle(
         TypedData::New(kTypedDataUint32ArrayCid, length + kExtraDigits, space));
-    if (!old_digits.IsNull()) {
+    if (old_digits.Length() > 0) {
       TypedData::Copy(new_digits, TypedData::data_offset(),
                       old_digits, TypedData::data_offset(),
                       old_digits.LengthInBytes());
     }
     set_digits(new_digits);
   }
 }
 
 
 void Bigint::Clamp() const {
@@ skipping 3188 matching lines @@
     result ^= raw;
     result.SetLength(len);
     if (len > 0) {
       memset(result.DataAddr(0), 0, lengthInBytes);
     }
   }
   return result.raw();
 }
 
 
+RawTypedData* TypedData::EmptyUint32Array(Isolate* isolate) {
+  ASSERT(isolate != NULL);
+  ASSERT(isolate->object_store() != NULL);
+  if (isolate->object_store()->empty_uint32_array() != TypedData::null()) {
+    // Already created.
+    return isolate->object_store()->empty_uint32_array();
+  }
+  const TypedData& array = TypedData::Handle(isolate,
+      TypedData::New(kTypedDataUint32ArrayCid, 0, Heap::kOld));
+  isolate->object_store()->set_empty_uint32_array(array);
+  return array.raw();
+}
+
+
 const char* TypedData::ToCString() const {
   return "TypedData";
 }
 
 
 void TypedData::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
@@ skipping 754 matching lines @@
   return tag_label.ToCString();
 }
 
 
 void UserTag::PrintJSONImpl(JSONStream* stream, bool ref) const {
   Instance::PrintJSONImpl(stream, ref);
 }
 
 
 }  // namespace dart