harmony_scoping: Implement lexical bindings at top level

src/contexts.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_CONTEXTS_H_
 #define V8_CONTEXTS_H_
 
 #include "src/heap/heap.h"
 #include "src/objects.h"
 
@@ skipping 165 matching lines @@
   V(NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE, JSFunction,                         \
     native_object_notifier_perform_change)                                     \
   V(SLOPPY_GENERATOR_FUNCTION_MAP_INDEX, Map, sloppy_generator_function_map)   \
   V(STRICT_GENERATOR_FUNCTION_MAP_INDEX, Map, strict_generator_function_map)   \
   V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, generator_object_prototype_map) \
   V(ITERATOR_RESULT_MAP_INDEX, Map, iterator_result_map)                       \
   V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map)                             \
   V(SET_ITERATOR_MAP_INDEX, Map, set_iterator_map)                             \
   V(ITERATOR_SYMBOL_INDEX, Symbol, iterator_symbol)                            \
   V(UNSCOPABLES_SYMBOL_INDEX, Symbol, unscopables_symbol)                      \
-  V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator)
+  V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator)            \
+  V(GLOBAL_CONTEXT_TABLE_INDEX, GlobalContextTable, global_context_table)
+
+
+class GlobalContextTable : public FixedArray {

[adamk, 2014/11/06 20:18:06]

Please add a comment for this class. What is it for? What's the layout?

[Dmitry Lomov (no reviews), 2014/11/07 10:18:48]

Done.

+ public:
+  // Conversions.
+  static GlobalContextTable* cast(Object* context) {
+    DCHECK(context->IsGlobalContextTable());
+    return reinterpret_cast<GlobalContextTable*>(context);
+  }
+
+  struct LookupResult {
+    int context_index;
+    int slot_index;
+    VariableMode mode;
+    InitializationFlag init_flag;
+    MaybeAssignedFlag maybe_assigned_flag;
+  };
+
+  int size() const { return Smi::cast(get(kSizeSlot))->value(); }

[adamk, 2014/11/06 20:18:05]

Just a question: are const methods that common? I do see a few in objects.h now
that I look. What's the best practice here?

[Dmitry Lomov (no reviews), 2014/11/07 10:18:47]

Make methods 'const' if possible is the parctice

+
+  static Handle<Context> GetContext(Handle<GlobalContextTable> table, int i) {
+    DCHECK(i < table->size());
+    return Handle<Context>::cast(FixedArray::get(table, i + 1));

[adamk, 2014/11/06 20:18:06]

This and the various other +1s in the .cc file might benefit from a constant or
a private helper method, but I could imagine that's too much overhead for a
simple case like this. I leave it up to you.

[Dmitry Lomov (no reviews), 2014/11/07 10:18:47]

Yes, I think it is too much fuss.

+  }
+
+  static bool Lookup(Handle<GlobalContextTable> table, Handle<String> name,

[adamk, 2014/11/06 20:18:06]

This method could use a comment, at least for the return value. It's notable
that result ends up with garbage in it when this returns false (MUST_USE_RESULT
wouldn't be a bad idea here for that reason).

[Dmitry Lomov (no reviews), 2014/11/07 10:18:47]

Done.

+                     LookupResult* result);
+
+  // table may be null.

[adamk, 2014/11/06 20:18:05]

Not clear what this means, it certainly can't be a null handle.

[Dmitry Lomov (no reviews), 2014/11/07 10:18:47]

Stray comment, removed.

+  static Handle<GlobalContextTable> Extend(Handle<GlobalContextTable> table,

[adamk, 2014/11/06 20:18:05]

MUST_USE_RESULT?

[Dmitry Lomov (no reviews), 2014/11/07 10:18:47]

Done.

+                                           Handle<Context> global_context);
+
+ private:
+  static const int kSizeSlot = 0;
+};

[adamk, 2014/11/06 20:18:05]

nit: DISALLOW_IMPLICIT_CONSTRUCTORS

[Dmitry Lomov (no reviews), 2014/11/07 10:18:47]

Done.

 
 // JSFunctions are pairs (context, function code), sometimes also called
 // closures. A Context object is used to represent function contexts and
 // dynamically pushed 'with' contexts (or 'scopes' in ECMA-262 speak).
 //
 // At runtime, the contexts build a stack in parallel to the execution
 // stack, with the top-most context being the current context. All contexts
 // have the following slots:
 //
 // [ closure   ]  This is the current function. It is the same for all
@@ skipping 156 matching lines @@
     NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE,
     SLOPPY_GENERATOR_FUNCTION_MAP_INDEX,
     STRICT_GENERATOR_FUNCTION_MAP_INDEX,
     GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX,
     ITERATOR_RESULT_MAP_INDEX,
     MAP_ITERATOR_MAP_INDEX,
     SET_ITERATOR_MAP_INDEX,
     ITERATOR_SYMBOL_INDEX,
     UNSCOPABLES_SYMBOL_INDEX,
     ARRAY_VALUES_ITERATOR_INDEX,
+    GLOBAL_CONTEXT_TABLE_INDEX,
 
     // Properties from here are treated as weak references by the full GC.
     // Scavenge treats them as strong references.
     OPTIMIZED_FUNCTIONS_LIST,  // Weak.
     OPTIMIZED_CODE_LIST,       // Weak.
     DEOPTIMIZED_CODE_LIST,     // Weak.
     MAP_CACHE_INDEX,           // Weak.
     NEXT_CONTEXT_LINK,         // Weak.
 
     // Total number of slots.
@@ skipping 175 matching lines @@
 
 #ifdef DEBUG
   // Bootstrapping-aware type checks.
   static bool IsBootstrappingOrValidParentContext(Object* object, Context* kid);
   static bool IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object);
 #endif
 
   STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize);
   STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 };
-
 } }  // namespace v8::internal
 
 #endif  // V8_CONTEXTS_H_