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

runtime/vm/verifier.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/verifier.h"
 
 #include "platform/assert.h"
 #include "vm/dart.h"
 #include "vm/dart_api_state.h"
 #include "vm/freelist.h"
@@ skipping 47 matching lines @@
 }
 
 void VerifyWeakPointersVisitor::VisitHandle(uword addr) {
   FinalizablePersistentHandle* handle =
       reinterpret_cast<FinalizablePersistentHandle*>(addr);
   RawObject* raw_obj = handle->raw();
   visitor_->VisitPointer(&raw_obj);
 }
 
 void VerifyPointersVisitor::VerifyPointers(MarkExpectation mark_expectation) {
-  NoSafepointScope no_safepoint;
   Thread* thread = Thread::Current();
   Isolate* isolate = thread->isolate();
+  HeapIterationScope iteration(thread);
   StackZone stack_zone(thread);
   ObjectSet* allocated_set = isolate->heap()->CreateAllocatedObjectSet(
       stack_zone.GetZone(), mark_expectation);
+
   VerifyPointersVisitor visitor(isolate, allocated_set);
   // Visit all strongly reachable objects.
-  isolate->IterateObjectPointers(&visitor, StackFrameIterator::kValidateFrames);
+  iteration.IterateObjectPointers(&visitor,
+                                  StackFrameIterator::kValidateFrames);
   VerifyWeakPointersVisitor weak_visitor(&visitor);
   // Visit weak handles and prologue weak handles.
   isolate->VisitWeakPersistentHandles(&weak_visitor);
 }
 
 #if defined(DEBUG)
 VerifyCanonicalVisitor::VerifyCanonicalVisitor(Thread* thread)
     : thread_(thread), instanceHandle_(Instance::Handle(thread->zone())) {}
 
 void VerifyCanonicalVisitor::VisitObject(RawObject* obj) {
   if (obj->GetClassId() >= kInstanceCid) {
     if (obj->IsCanonical()) {
       instanceHandle_ ^= obj;
       const bool is_canonical = instanceHandle_.CheckIsCanonical(thread_);
       if (!is_canonical) {
         OS::PrintErr("Instance `%s` is not canonical!\n",
                      instanceHandle_.ToCString());
       }
       ASSERT(is_canonical);
     }
   }
 }
 #endif  // defined(DEBUG)
 
 }  // namespace dart