Guard against undefined fields in global context.

src/heap.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 626 matching lines @@
 }
 
 
 void Heap::ClearJSFunctionResultCaches() {
   if (isolate_->bootstrapper()->IsActive()) return;
 
   Object* context = global_contexts_list_;
   while (!context->IsUndefined()) {
     // Get the caches for this context:
     FixedArray* caches =
       Context::cast(context)->jsfunction_result_caches();

[Vyacheslav Egorov (Chromium), 2011/12/13 12:26:20]

Should not you guard here instead of guarding below? 

(set_jsfunction_result_caches is called once the cache is fully constructed).

also please comment why we need to guard against undefined.

[ulan, 2011/12/13 13:02:58]

Done.

     // Clear the caches:
     int length = caches->length();
     for (int i = 0; i < length; i++) {
-      JSFunctionResultCache::cast(caches->get(i))->Clear();
+      Object* cache = caches->get(i);
+      if (!cache->IsUndefined()) {
+        JSFunctionResultCache::cast(cache)->Clear();
+      }
     }
     // Get the next context:
     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
   }
 }
 
 
 
 void Heap::ClearNormalizedMapCaches() {
   if (isolate_->bootstrapper()->IsActive() &&
       !incremental_marking()->IsMarking()) {
     return;
   }
 
   Object* context = global_contexts_list_;
   while (!context->IsUndefined()) {
-    Context::cast(context)->normalized_map_cache()->Clear();
+    int index = Context::NORMALIZED_MAP_CACHE_INDEX;

[Vyacheslav Egorov (Chromium), 2011/12/13 12:26:20]

I don't think we need separate variable just for index.

[ulan, 2011/12/13 13:02:58]

Done.

+    Object* cache = Context::cast(context)->get(index);
+    if (!cache->IsUndefined()) {

[Vyacheslav Egorov (Chromium), 2011/12/13 12:26:20]

please comment why we need to guard against partial initialized objects.

[ulan, 2011/12/13 13:02:58]

Done.

+      NormalizedMapCache::cast(cache)->Clear();
+    }
     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
   }
 }
 
 
 void Heap::UpdateSurvivalRateTrend(int start_new_space_size) {
   double survival_rate =
       (static_cast<double>(young_survivors_after_last_gc_) * 100) /
       start_new_space_size;
 
@@ skipping 5912 matching lines @@
   isolate_->heap()->store_buffer()->Compact();
   isolate_->heap()->store_buffer()->Filter(MemoryChunk::ABOUT_TO_BE_FREED);
   for (chunk = chunks_queued_for_free_; chunk != NULL; chunk = next) {
     next = chunk->next_chunk();
     isolate_->memory_allocator()->Free(chunk);
   }
   chunks_queued_for_free_ = NULL;
 }
 
 } }  // namespace v8::internal