Debug garbage collector does not correctly remove cross-gen garbage

runtime/vm/heap.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/heap.h"
 
 #include "platform/assert.h"
 #include "platform/utils.h"
 #include "vm/flags.h"
 #include "vm/isolate.h"
@@ skipping 20 matching lines @@
            intptr_t max_new_gen_semi_words,
            intptr_t max_old_gen_words,
            intptr_t max_external_words)
     : isolate_(isolate),
       new_space_(this, max_new_gen_semi_words, kNewObjectAlignmentOffset),
       old_space_(this, max_old_gen_words, max_external_words),
       barrier_(new Monitor()),
       barrier_done_(new Monitor()),
       read_only_(false),
       gc_new_space_in_progress_(false),
-      gc_old_space_in_progress_(false) {
+      gc_old_space_in_progress_(false),
+      debug_gc_in_progress_(false) {
   UpdateGlobalMaxUsed();
   for (int sel = 0; sel < kNumWeakSelectors; sel++) {
     new_weak_tables_[sel] = new WeakTable();
     old_weak_tables_[sel] = new WeakTable();
   }
   stats_.num_ = 0;
 }
 
 
 Heap::~Heap() {
@@ skipping 385 matching lines @@
     CollectOldSpaceGarbage(thread, kInvokeApiCallbacks, kOldSpace);
   } else {
     ASSERT(space == kNew);
     CollectNewSpaceGarbage(thread, kInvokeApiCallbacks, kNewSpace);
   }
 }
 
 
 void Heap::CollectAllGarbage() {
   Thread* thread = Thread::Current();
+  debug_gc_in_progress_ = true;
+  CollectOldSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
   CollectNewSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
-  CollectOldSpaceGarbage(thread, kInvokeApiCallbacks, kFull);
+  debug_gc_in_progress_ = false;
 }
 
 
 void Heap::WaitForSweeperTasks(Thread* thread) {
   MonitorLocker ml(old_space_.tasks_lock());
   while (old_space_.tasks() > 0) {
     ml.WaitWithSafepointCheck(thread);
   }
 }
 
@@ skipping 395 matching lines @@
   Dart::vm_isolate()->heap()->WriteProtect(false);
 }
 
 
 WritableVMIsolateScope::~WritableVMIsolateScope() {
   ASSERT(Dart::vm_isolate()->heap()->UsedInWords(Heap::kNew) == 0);
   Dart::vm_isolate()->heap()->WriteProtect(true);
 }
 
 }  // namespace dart