[vm, gc] Require a safepoint for heap iteration.

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/become.h"
@@ skipping 1098 matching lines @@
 
   // Set up names for the pseudo-classes for free list elements and forwarding
   // corpses. Mainly this makes VM debugging easier.
   cls = isolate->class_table()->At(kFreeListElement);
   cls.set_name(Symbols::FreeListElement());
   cls = isolate->class_table()->At(kForwardingCorpse);
   cls.set_name(Symbols::ForwardingCorpse());
 
   {
     ASSERT(isolate == Dart::vm_isolate());
-    WritableVMIsolateScope scope(Thread::Current());
+    Thread* thread = Thread::Current();
+    WritableVMIsolateScope scope(thread);
+    HeapIterationScope iteration(thread);
     FinalizeVMIsolateVisitor premarker;
     ASSERT(isolate->heap()->UsedInWords(Heap::kNew) == 0);
-    isolate->heap()->IterateOldObjectsNoImagePages(&premarker);
+    iteration.IterateOldObjectsNoImagePages(&premarker);
     // Make the VM isolate read-only again after setting all objects as marked.
     // Note objects in image pages are already pre-marked.
   }
 }
 
 void Object::set_vm_isolate_snapshot_object_table(const Array& table) {
   ASSERT(Isolate::Current() == Dart::vm_isolate());
   *vm_isolate_snapshot_object_table_ = table.raw();
 }
 
@@ skipping 12986 matching lines @@
 
 bool Code::SlowFindRawCodeVisitor::FindObject(RawObject* raw_obj) const {
   return RawCode::ContainsPC(raw_obj, pc_);
 }
 
 RawCode* Code::LookupCodeInIsolate(Isolate* isolate, uword pc) {
   ASSERT((isolate == Isolate::Current()) || (isolate == Dart::vm_isolate()));
   if (isolate->heap() == NULL) {
     return Code::null();
   }
-  NoSafepointScope no_safepoint;
+  HeapIterationScope heap_iteration_scope(Thread::Current());
   SlowFindRawCodeVisitor visitor(pc);
   RawObject* needle = isolate->heap()->FindOldObject(&visitor);
   if (needle != Code::null()) {
     return static_cast<RawCode*>(needle);
   }
   return Code::null();
 }
 
 RawCode* Code::LookupCode(uword pc) {
   return LookupCodeInIsolate(Isolate::Current(), pc);
@@ skipping 8406 matching lines @@
   }
   return UserTag::null();
 }
 
 const char* UserTag::ToCString() const {
   const String& tag_label = String::Handle(label());
   return tag_label.ToCString();
 }
 
 }  // namespace dart