Fix Dartium DEBUG failures by ensuring proper scoping within GC prologue/epilogue.

runtime/vm/scavenger.cc

 // Copyright (c) 2011, 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/scavenger.h"
 
 #include <algorithm>
 #include <map>
 #include <utility>
 
@@ skipping 457 matching lines @@
     // isolate to finish scavenge, etc.).
     FATAL("Out of memory.\n");
   }
   top_ = FirstObjectStart();
   resolved_top_ = top_;
   end_ = to_->end();
 }
 
 
 void Scavenger::Epilogue(Isolate* isolate,
-                         ScavengerVisitor* visitor,
                          bool invoke_api_callbacks) {
   // All objects in the to space have been copied from the from space at this
   // moment.
   double avg_frac = stats_history_.Get(0).PromoCandidatesSuccessFraction();
   if (stats_history_.Size() >= 2) {
     // Previous scavenge is only given half as much weight.
     avg_frac += 0.5 * stats_history_.Get(1).PromoCandidatesSuccessFraction();
     avg_frac /= 1.0 + 0.5;  // Normalize.
   }
   if (avg_frac < (FLAG_early_tenuring_threshold / 100.0)) {
@@ skipping 322 matching lines @@
     OS::PrintErr("Verifying before Scavenge...");
     heap_->Verify(kForbidMarked);
     OS::PrintErr(" done.\n");
   }
 
   // Prepare for a scavenge.
   SpaceUsage usage_before = GetCurrentUsage();
   intptr_t promo_candidate_words =
       (survivor_end_ - FirstObjectStart()) / kWordSize;
   Prologue(isolate, invoke_api_callbacks);
-  const bool prologue_weak_are_strong = !invoke_api_callbacks;
+  // The API prologue/epilogue may create/destroy zones, so we must not
+  // depend on zone allocations surviving beyond the epilogue callback.
+  {
+    StackZone zone(isolate);
+    // Setup the visitor and run the scavenge.
+    ScavengerVisitor visitor(isolate, this);
+    page_space->AcquireDataLock();
+    const bool prologue_weak_are_strong = !invoke_api_callbacks;
+    IterateRoots(isolate, &visitor, prologue_weak_are_strong);
+    int64_t start = OS::GetCurrentTimeMicros();
+    ProcessToSpace(&visitor);
+    int64_t middle = OS::GetCurrentTimeMicros();
+    IterateWeakReferences(isolate, &visitor);
+    ScavengerWeakVisitor weak_visitor(this, prologue_weak_are_strong);
+    // Include the prologue weak handles, since we must process any promotion.
+    const bool visit_prologue_weak_handles = true;
+    IterateWeakRoots(isolate, &weak_visitor, visit_prologue_weak_handles);
+    visitor.Finalize();
+    ProcessWeakTables();
+    page_space->ReleaseDataLock();
 
-  // Setup the visitor and run the scavenge.
-  ScavengerVisitor visitor(isolate, this);
-  page_space->AcquireDataLock();
-  IterateRoots(isolate, &visitor, prologue_weak_are_strong);
-  int64_t start = OS::GetCurrentTimeMicros();
-  ProcessToSpace(&visitor);
-  int64_t middle = OS::GetCurrentTimeMicros();
-  IterateWeakReferences(isolate, &visitor);
-  ScavengerWeakVisitor weak_visitor(this, prologue_weak_are_strong);
-  // Include the prologue weak handles, since we must process any promotion.
-  const bool visit_prologue_weak_handles = true;
-  IterateWeakRoots(isolate, &weak_visitor, visit_prologue_weak_handles);
-  visitor.Finalize();
-  ProcessWeakTables();
-  page_space->ReleaseDataLock();
-
-  // Scavenge finished. Run accounting and epilogue.
-  int64_t end = OS::GetCurrentTimeMicros();
-  heap_->RecordTime(kProcessToSpace, middle - start);
-  heap_->RecordTime(kIterateWeaks, end - middle);
-  stats_history_.Add(ScavengeStats(start, end,
-                                   usage_before, GetCurrentUsage(),
-                                   promo_candidate_words,
-                                   visitor.bytes_promoted() >> kWordSizeLog2));
-  Epilogue(isolate, &visitor, invoke_api_callbacks);
+    // Scavenge finished. Run accounting.
+    int64_t end = OS::GetCurrentTimeMicros();
+    heap_->RecordTime(kProcessToSpace, middle - start);
+    heap_->RecordTime(kIterateWeaks, end - middle);
+    stats_history_.Add(
+        ScavengeStats(start, end,
+                      usage_before, GetCurrentUsage(),
+                      promo_candidate_words,
+                      visitor.bytes_promoted() >> kWordSizeLog2));
+  }
+  Epilogue(isolate, invoke_api_callbacks);
 
   // TODO(koda): Make verification more compatible with concurrent sweep.
   if (FLAG_verify_after_gc && !FLAG_concurrent_sweep) {
     OS::PrintErr("Verifying after Scavenge...");
     heap_->Verify(kForbidMarked);
     OS::PrintErr(" done.\n");
   }
 
   // Done scavenging. Reset the marker.
   ASSERT(scavenging_);
@@ skipping 41 matching lines @@
 }
 
 
 void Scavenger::FreeExternal(intptr_t size) {
   ASSERT(size >= 0);
   external_size_ -= size;
   ASSERT(external_size_ >= 0);
 }
 
 }  // namespace dart