Avoid calling potentially-allocating PrintJSON methods when iterating over heap.

runtime/vm/object_test.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 "platform/globals.h"
 
 #include "vm/assembler.h"
 #include "vm/bigint_operations.h"
 #include "vm/class_finalizer.h"
 #include "vm/dart_api_impl.h"
@@ skipping 4151 matching lines @@
 
   // Truncation, limit is in u-escape
   result = Dart_GetField(lib, NewString("toolong3"));
   EXPECT_VALID(result);
   obj ^= Api::UnwrapHandle(result);
   EXPECT_STREQ("\"012345678901234567890123456789\"...",
                obj.ToUserCString(40));
 }
 
 
-class JSONTypeVerifier : public ObjectVisitor {
+class ObjectAccumulator : public ObjectVisitor {
  public:
-  JSONTypeVerifier() : ObjectVisitor(Isolate::Current()) {}
-  virtual ~JSONTypeVerifier() { }
+  explicit ObjectAccumulator(GrowableArray<Object*>* objects)
+      : ObjectVisitor(Isolate::Current()), objects_(objects) {}
+  virtual ~ObjectAccumulator() { }
   virtual void VisitObject(RawObject* obj) {
     // Free-list elements cannot even be wrapped in handles.
     if (obj->IsFreeListElement()) {
       return;
     }
     Object& handle = Object::Handle(obj);
     // Skip some common simple objects to run in reasonable time.
     if (handle.IsString() ||
         handle.IsArray() ||
         handle.IsLiteralToken()) {
       return;
     }
-    JSONStream js;
-    handle.PrintJSON(&js, false);
-    EXPECT_SUBSTRING("\"type\":", js.ToCString());
+    objects_->Add(&handle);
   }
+ private:
+  GrowableArray<Object*>* objects_;
 };
 
 
 TEST_CASE(PrintJSON) {
   Heap* heap = Isolate::Current()->heap();
   heap->CollectAllGarbage();
-  JSONTypeVerifier verifier;
-  heap->IterateObjects(&verifier);
+  GrowableArray<Object*> objects;
+  ObjectAccumulator acc(&objects);
+  heap->IterateObjects(&acc);
+  for (intptr_t i = 0; i < objects.length(); ++i) {
+    JSONStream js;
+    objects[i]->PrintJSON(&js, false);
+    EXPECT_SUBSTRING("\"type\":", js.ToCString());
+  }
 }
 
 
 TEST_CASE(InstanceEquality) {
   // Test that Instance::OperatorEquals can call a user-defined operator==.
   const char* kScript =
       "class A {\n"
       "  bool operator==(A other) { return true; }\n"
       "}\n"
       "main() {\n"
@@ skipping 35 matching lines @@
   EXPECT_VALID(h_result);
   Integer& result = Integer::Handle();
   result ^= Api::UnwrapHandle(h_result);
   String& foo = String::Handle(String::New("foo"));
   Integer& expected = Integer::Handle();
   expected ^= foo.HashCode();
   EXPECT(result.IsIdenticalTo(expected));
 }
 
 }  // namespace dart