src/v8/src/contexts.h

   1 // Copyright 2012 the V8 project authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef V8_CONTEXTS_H_
   6 #define V8_CONTEXTS_H_
   7
   8 #include "src/heap/heap.h"
   9 #include "src/objects.h"
  10
  11 namespace v8 {
  12 namespace internal {
  13
  14
  15 enum ContextLookupFlags {
  16   FOLLOW_CONTEXT_CHAIN = 1,
  17   FOLLOW_PROTOTYPE_CHAIN = 2,
  18
  19   DONT_FOLLOW_CHAINS = 0,
  20   FOLLOW_CHAINS = FOLLOW_CONTEXT_CHAIN | FOLLOW_PROTOTYPE_CHAIN
  21 };
  22
  23
  24 // ES5 10.2 defines lexical environments with mutable and immutable bindings.
  25 // Immutable bindings have two states, initialized and uninitialized, and
  26 // their state is changed by the InitializeImmutableBinding method. The
  27 // BindingFlags enum represents information if a binding has definitely been
  28 // initialized. A mutable binding does not need to be checked and thus has
  29 // the BindingFlag MUTABLE_IS_INITIALIZED.
  30 //
  31 // There are two possibilities for immutable bindings
  32 //  * 'const' declared variables. They are initialized when evaluating the
  33 //    corresponding declaration statement. They need to be checked for being
  34 //    initialized and thus get the flag IMMUTABLE_CHECK_INITIALIZED.
  35 //  * The function name of a named function literal. The binding is immediately
  36 //    initialized when entering the function and thus does not need to be
  37 //    checked. it gets the BindingFlag IMMUTABLE_IS_INITIALIZED.
  38 // Accessing an uninitialized binding produces the undefined value.
  39 //
  40 // The harmony proposal for block scoped bindings also introduces the
  41 // uninitialized state for mutable bindings.
  42 //  * A 'let' declared variable. They are initialized when evaluating the
  43 //    corresponding declaration statement. They need to be checked for being
  44 //    initialized and thus get the flag MUTABLE_CHECK_INITIALIZED.
  45 //  * A 'var' declared variable. It is initialized immediately upon creation
  46 //    and thus doesn't need to be checked. It gets the flag
  47 //    MUTABLE_IS_INITIALIZED.
  48 //  * Catch bound variables, function parameters and variables introduced by
  49 //    function declarations are initialized immediately and do not need to be
  50 //    checked. Thus they get the flag MUTABLE_IS_INITIALIZED.
  51 // Immutable bindings in harmony mode get the _HARMONY flag variants. Accessing
  52 // an uninitialized binding produces a reference error.
  53 //
  54 // In V8 uninitialized bindings are set to the hole value upon creation and set
  55 // to a different value upon initialization.
  56 enum BindingFlags {
  57   MUTABLE_IS_INITIALIZED,
  58   MUTABLE_CHECK_INITIALIZED,
  59   IMMUTABLE_IS_INITIALIZED,
  60   IMMUTABLE_CHECK_INITIALIZED,
  61   IMMUTABLE_IS_INITIALIZED_HARMONY,
  62   IMMUTABLE_CHECK_INITIALIZED_HARMONY,
  63   MISSING_BINDING
  64 };
  65
  66
  67 // Heap-allocated activation contexts.
  68 //
  69 // Contexts are implemented as FixedArray objects; the Context
  70 // class is a convenience interface casted on a FixedArray object.
  71 //
  72 // Note: Context must have no virtual functions and Context objects
  73 // must always be allocated via Heap::AllocateContext() or
  74 // Factory::NewContext.
  75
  76 #define NATIVE_CONTEXT_FIELDS(V)                                               \
  77   V(GLOBAL_PROXY_INDEX, JSObject, global_proxy_object)                         \
  78   V(SECURITY_TOKEN_INDEX, Object, security_token)                              \
  79   V(BOOLEAN_FUNCTION_INDEX, JSFunction, boolean_function)                      \
  80   V(NUMBER_FUNCTION_INDEX, JSFunction, number_function)                        \
  81   V(STRING_FUNCTION_INDEX, JSFunction, string_function)                        \
  82   V(STRING_FUNCTION_PROTOTYPE_MAP_INDEX, Map, string_function_prototype_map)   \
  83   V(SYMBOL_FUNCTION_INDEX, JSFunction, symbol_function)                        \
  84   V(OBJECT_FUNCTION_INDEX, JSFunction, object_function)                        \
  85   V(INTERNAL_ARRAY_FUNCTION_INDEX, JSFunction, internal_array_function)        \
  86   V(ARRAY_FUNCTION_INDEX, JSFunction, array_function)                          \
  87   V(JS_ARRAY_MAPS_INDEX, Object, js_array_maps)                                \
  88   V(DATE_FUNCTION_INDEX, JSFunction, date_function)                            \
  89   V(JSON_OBJECT_INDEX, JSObject, json_object)                                  \
  90   V(REGEXP_FUNCTION_INDEX, JSFunction, regexp_function)                        \
  91   V(INITIAL_OBJECT_PROTOTYPE_INDEX, JSObject, initial_object_prototype)        \
  92   V(INITIAL_ARRAY_PROTOTYPE_INDEX, JSObject, initial_array_prototype)          \
  93   V(CREATE_DATE_FUN_INDEX, JSFunction, create_date_fun)                        \
  94   V(TO_NUMBER_FUN_INDEX, JSFunction, to_number_fun)                            \
  95   V(TO_STRING_FUN_INDEX, JSFunction, to_string_fun)                            \
  96   V(TO_DETAIL_STRING_FUN_INDEX, JSFunction, to_detail_string_fun)              \
  97   V(TO_OBJECT_FUN_INDEX, JSFunction, to_object_fun)                            \
  98   V(TO_INTEGER_FUN_INDEX, JSFunction, to_integer_fun)                          \
  99   V(TO_UINT32_FUN_INDEX, JSFunction, to_uint32_fun)                            \
 100   V(TO_INT32_FUN_INDEX, JSFunction, to_int32_fun)                              \
 101   V(GLOBAL_EVAL_FUN_INDEX, JSFunction, global_eval_fun)                        \
 102   V(INSTANTIATE_FUN_INDEX, JSFunction, instantiate_fun)                        \
 103   V(CONFIGURE_INSTANCE_FUN_INDEX, JSFunction, configure_instance_fun)          \
 104   V(MATH_ABS_FUN_INDEX, JSFunction, math_abs_fun)                              \
 105   V(MATH_ACOS_FUN_INDEX, JSFunction, math_acos_fun)                            \
 106   V(MATH_ASIN_FUN_INDEX, JSFunction, math_asin_fun)                            \
 107   V(MATH_ATAN_FUN_INDEX, JSFunction, math_atan_fun)                            \
 108   V(MATH_ATAN2_FUN_INDEX, JSFunction, math_atan2_fun)                          \
 109   V(MATH_CEIL_FUN_INDEX, JSFunction, math_ceil_fun)                            \
 110   V(MATH_COS_FUN_INDEX, JSFunction, math_cos_fun)                              \
 111   V(MATH_EXP_FUN_INDEX, JSFunction, math_exp_fun)                              \
 112   V(MATH_FLOOR_FUN_INDEX, JSFunction, math_floor_fun)                          \
 113   V(MATH_IMUL_FUN_INDEX, JSFunction, math_imul_fun)                            \
 114   V(MATH_LOG_FUN_INDEX, JSFunction, math_log_fun)                              \
 115   V(MATH_MAX_FUN_INDEX, JSFunction, math_max_fun)                              \
 116   V(MATH_MIN_FUN_INDEX, JSFunction, math_min_fun)                              \
 117   V(MATH_POW_FUN_INDEX, JSFunction, math_pow_fun)                              \
 118   V(MATH_RANDOM_FUN_INDEX, JSFunction, math_random_fun)                        \
 119   V(MATH_ROUND_FUN_INDEX, JSFunction, math_round_fun)                          \
 120   V(MATH_SIN_FUN_INDEX, JSFunction, math_sin_fun)                              \
 121   V(MATH_SQRT_FUN_INDEX, JSFunction, math_sqrt_fun)                            \
 122   V(MATH_TAN_FUN_INDEX, JSFunction, math_tan_fun)                              \
 123   V(ARRAY_BUFFER_FUN_INDEX, JSFunction, array_buffer_fun)                      \
 124   V(UINT8_ARRAY_FUN_INDEX, JSFunction, uint8_array_fun)                        \
 125   V(INT8_ARRAY_FUN_INDEX, JSFunction, int8_array_fun)                          \
 126   V(UINT16_ARRAY_FUN_INDEX, JSFunction, uint16_array_fun)                      \
 127   V(INT16_ARRAY_FUN_INDEX, JSFunction, int16_array_fun)                        \
 128   V(UINT32_ARRAY_FUN_INDEX, JSFunction, uint32_array_fun)                      \
 129   V(INT32_ARRAY_FUN_INDEX, JSFunction, int32_array_fun)                        \
 130   V(FLOAT32_ARRAY_FUN_INDEX, JSFunction, float32_array_fun)                    \
 131   V(FLOAT64_ARRAY_FUN_INDEX, JSFunction, float64_array_fun)                    \
 132   V(UINT8_CLAMPED_ARRAY_FUN_INDEX, JSFunction, uint8_clamped_array_fun)        \
 133   V(INT8_ARRAY_EXTERNAL_MAP_INDEX, Map, int8_array_external_map)               \
 134   V(UINT8_ARRAY_EXTERNAL_MAP_INDEX, Map, uint8_array_external_map)             \
 135   V(INT16_ARRAY_EXTERNAL_MAP_INDEX, Map, int16_array_external_map)             \
 136   V(UINT16_ARRAY_EXTERNAL_MAP_INDEX, Map, uint16_array_external_map)           \
 137   V(INT32_ARRAY_EXTERNAL_MAP_INDEX, Map, int32_array_external_map)             \
 138   V(UINT32_ARRAY_EXTERNAL_MAP_INDEX, Map, uint32_array_external_map)           \
 139   V(FLOAT32_ARRAY_EXTERNAL_MAP_INDEX, Map, float32_array_external_map)         \
 140   V(FLOAT64_ARRAY_EXTERNAL_MAP_INDEX, Map, float64_array_external_map)         \
 141   V(UINT8_CLAMPED_ARRAY_EXTERNAL_MAP_INDEX, Map,                               \
 142     uint8_clamped_array_external_map)                                          \
 143   V(DATA_VIEW_FUN_INDEX, JSFunction, data_view_fun)                            \
 144   V(SLOPPY_FUNCTION_MAP_INDEX, Map, sloppy_function_map)                       \
 145   V(SLOPPY_FUNCTION_WITH_READONLY_PROTOTYPE_MAP_INDEX, Map,                    \
 146     sloppy_function_with_readonly_prototype_map)                               \
 147   V(STRICT_FUNCTION_MAP_INDEX, Map, strict_function_map)                       \
 148   V(SLOPPY_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX, Map,                          \
 149     sloppy_function_without_prototype_map)                                     \
 150   V(STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX, Map,                          \
 151     strict_function_without_prototype_map)                                     \
 152   V(BOUND_FUNCTION_MAP_INDEX, Map, bound_function_map)                         \
 153   V(REGEXP_RESULT_MAP_INDEX, Map, regexp_result_map)                           \
 154   V(SLOPPY_ARGUMENTS_MAP_INDEX, Map, sloppy_arguments_map)                     \
 155   V(ALIASED_ARGUMENTS_MAP_INDEX, Map, aliased_arguments_map)                   \
 156   V(STRICT_ARGUMENTS_MAP_INDEX, Map, strict_arguments_map)                     \
 157   V(MESSAGE_LISTENERS_INDEX, JSObject, message_listeners)                      \
 158   V(MAKE_MESSAGE_FUN_INDEX, JSFunction, make_message_fun)                      \
 159   V(GET_STACK_TRACE_LINE_INDEX, JSFunction, get_stack_trace_line_fun)          \
 160   V(CONFIGURE_GLOBAL_INDEX, JSFunction, configure_global_fun)                  \
 161   V(FUNCTION_CACHE_INDEX, JSObject, function_cache)                            \
 162   V(JSFUNCTION_RESULT_CACHES_INDEX, FixedArray, jsfunction_result_caches)      \
 163   V(NORMALIZED_MAP_CACHE_INDEX, Object, normalized_map_cache)                  \
 164   V(RUNTIME_CONTEXT_INDEX, Context, runtime_context)                           \
 165   V(CALL_AS_FUNCTION_DELEGATE_INDEX, JSFunction, call_as_function_delegate)    \
 166   V(CALL_AS_CONSTRUCTOR_DELEGATE_INDEX, JSFunction,                            \
 167     call_as_constructor_delegate)                                              \
 168   V(SCRIPT_FUNCTION_INDEX, JSFunction, script_function)                        \
 169   V(OPAQUE_REFERENCE_FUNCTION_INDEX, JSFunction, opaque_reference_function)    \
 170   V(CONTEXT_EXTENSION_FUNCTION_INDEX, JSFunction, context_extension_function)  \
 171   V(MAP_CACHE_INDEX, Object, map_cache)                                        \
 172   V(EMBEDDER_DATA_INDEX, FixedArray, embedder_data)                            \
 173   V(ALLOW_CODE_GEN_FROM_STRINGS_INDEX, Object, allow_code_gen_from_strings)    \
 174   V(ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX, Object,                     \
 175     error_message_for_code_gen_from_strings)                                   \
 176   V(IS_PROMISE_INDEX, JSFunction, is_promise)                                  \
 177   V(PROMISE_CREATE_INDEX, JSFunction, promise_create)                          \
 178   V(PROMISE_RESOLVE_INDEX, JSFunction, promise_resolve)                        \
 179   V(PROMISE_REJECT_INDEX, JSFunction, promise_reject)                          \
 180   V(PROMISE_CHAIN_INDEX, JSFunction, promise_chain)                            \
 181   V(PROMISE_CATCH_INDEX, JSFunction, promise_catch)                            \
 182   V(PROMISE_THEN_INDEX, JSFunction, promise_then)                              \
 183   V(TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX, JSFunction,                         \
 184     to_complete_property_descriptor)                                           \
 185   V(DERIVED_HAS_TRAP_INDEX, JSFunction, derived_has_trap)                      \
 186   V(DERIVED_GET_TRAP_INDEX, JSFunction, derived_get_trap)                      \
 187   V(DERIVED_SET_TRAP_INDEX, JSFunction, derived_set_trap)                      \
 188   V(PROXY_ENUMERATE_INDEX, JSFunction, proxy_enumerate)                        \
 189   V(OBSERVERS_NOTIFY_CHANGE_INDEX, JSFunction, observers_notify_change)        \
 190   V(OBSERVERS_ENQUEUE_SPLICE_INDEX, JSFunction, observers_enqueue_splice)      \
 191   V(OBSERVERS_BEGIN_SPLICE_INDEX, JSFunction, observers_begin_perform_splice)  \
 192   V(OBSERVERS_END_SPLICE_INDEX, JSFunction, observers_end_perform_splice)      \
 193   V(NATIVE_OBJECT_OBSERVE_INDEX, JSFunction, native_object_observe)            \
 194   V(NATIVE_OBJECT_GET_NOTIFIER_INDEX, JSFunction, native_object_get_notifier)  \
 195   V(NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE, JSFunction,                         \
 196     native_object_notifier_perform_change)                                     \
 197   V(SLOPPY_GENERATOR_FUNCTION_MAP_INDEX, Map, sloppy_generator_function_map)   \
 198   V(STRICT_GENERATOR_FUNCTION_MAP_INDEX, Map, strict_generator_function_map)   \
 199   V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, generator_object_prototype_map) \
 200   V(ITERATOR_RESULT_MAP_INDEX, Map, iterator_result_map)                       \
 201   V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map)                             \
 202   V(SET_ITERATOR_MAP_INDEX, Map, set_iterator_map)                             \
 203   V(ITERATOR_SYMBOL_INDEX, Symbol, iterator_symbol)                            \
 204   V(UNSCOPABLES_SYMBOL_INDEX, Symbol, unscopables_symbol)                      \
 205   V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator)
 206
 207 // JSFunctions are pairs (context, function code), sometimes also called
 208 // closures. A Context object is used to represent function contexts and
 209 // dynamically pushed 'with' contexts (or 'scopes' in ECMA-262 speak).
 210 //
 211 // At runtime, the contexts build a stack in parallel to the execution
 212 // stack, with the top-most context being the current context. All contexts
 213 // have the following slots:
 214 //
 215 // [ closure   ]  This is the current function. It is the same for all
 216 //                contexts inside a function. It provides access to the
 217 //                incoming context (i.e., the outer context, which may
 218 //                or may not become the current function's context), and
 219 //                it provides access to the functions code and thus it's
 220 //                scope information, which in turn contains the names of
 221 //                statically allocated context slots. The names are needed
 222 //                for dynamic lookups in the presence of 'with' or 'eval'.
 223 //
 224 // [ previous  ]  A pointer to the previous context. It is NULL for
 225 //                function contexts, and non-NULL for 'with' contexts.
 226 //                Used to implement the 'with' statement.
 227 //
 228 // [ extension ]  A pointer to an extension JSObject, or NULL. Used to
 229 //                implement 'with' statements and dynamic declarations
 230 //                (through 'eval'). The object in a 'with' statement is
 231 //                stored in the extension slot of a 'with' context.
 232 //                Dynamically declared variables/functions are also added
 233 //                to lazily allocated extension object. Context::Lookup
 234 //                searches the extension object for properties.
 235 //                For global and block contexts, contains the respective
 236 //                ScopeInfo.
 237 //                For module contexts, points back to the respective JSModule.
 238 //
 239 // [ global_object ]  A pointer to the global object. Provided for quick
 240 //                access to the global object from inside the code (since
 241 //                we always have a context pointer).
 242 //
 243 // In addition, function contexts may have statically allocated context slots
 244 // to store local variables/functions that are accessed from inner functions
 245 // (via static context addresses) or through 'eval' (dynamic context lookups).
 246 // The native context contains additional slots for fast access to native
 247 // properties.
 248 //
 249 // Finally, with Harmony scoping, the JSFunction representing a top level
 250 // script will have the GlobalContext rather than a FunctionContext.
 251
 252 class Context: public FixedArray {
 253  public:
 254   // Conversions.
 255   static Context* cast(Object* context) {
 256     DCHECK(context->IsContext());
 257     return reinterpret_cast<Context*>(context);
 258   }
 259
 260   // The default context slot layout; indices are FixedArray slot indices.
 261   enum {
 262     // These slots are in all contexts.
 263     CLOSURE_INDEX,
 264     PREVIOUS_INDEX,
 265     // The extension slot is used for either the global object (in global
 266     // contexts), eval extension object (function contexts), subject of with
 267     // (with contexts), or the variable name (catch contexts), the serialized
 268     // scope info (block contexts), or the module instance (module contexts).
 269     EXTENSION_INDEX,
 270     GLOBAL_OBJECT_INDEX,
 271     MIN_CONTEXT_SLOTS,
 272
 273     // This slot holds the thrown value in catch contexts.
 274     THROWN_OBJECT_INDEX = MIN_CONTEXT_SLOTS,
 275
 276     // These slots are only in native contexts.
 277     GLOBAL_PROXY_INDEX = MIN_CONTEXT_SLOTS,
 278     SECURITY_TOKEN_INDEX,
 279     SLOPPY_ARGUMENTS_MAP_INDEX,
 280     ALIASED_ARGUMENTS_MAP_INDEX,
 281     STRICT_ARGUMENTS_MAP_INDEX,
 282     REGEXP_RESULT_MAP_INDEX,
 283     SLOPPY_FUNCTION_MAP_INDEX,
 284     SLOPPY_FUNCTION_WITH_READONLY_PROTOTYPE_MAP_INDEX,
 285     STRICT_FUNCTION_MAP_INDEX,
 286     SLOPPY_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX,
 287     STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX,
 288     BOUND_FUNCTION_MAP_INDEX,
 289     INITIAL_OBJECT_PROTOTYPE_INDEX,
 290     INITIAL_ARRAY_PROTOTYPE_INDEX,
 291     BOOLEAN_FUNCTION_INDEX,
 292     NUMBER_FUNCTION_INDEX,
 293     STRING_FUNCTION_INDEX,
 294     STRING_FUNCTION_PROTOTYPE_MAP_INDEX,
 295     SYMBOL_FUNCTION_INDEX,
 296     OBJECT_FUNCTION_INDEX,
 297     INTERNAL_ARRAY_FUNCTION_INDEX,
 298     ARRAY_FUNCTION_INDEX,
 299     JS_ARRAY_MAPS_INDEX,
 300     DATE_FUNCTION_INDEX,
 301     JSON_OBJECT_INDEX,
 302     REGEXP_FUNCTION_INDEX,
 303     CREATE_DATE_FUN_INDEX,
 304     TO_NUMBER_FUN_INDEX,
 305     TO_STRING_FUN_INDEX,
 306     TO_DETAIL_STRING_FUN_INDEX,
 307     TO_OBJECT_FUN_INDEX,
 308     TO_INTEGER_FUN_INDEX,
 309     TO_UINT32_FUN_INDEX,
 310     TO_INT32_FUN_INDEX,
 311     TO_BOOLEAN_FUN_INDEX,
 312     GLOBAL_EVAL_FUN_INDEX,
 313     INSTANTIATE_FUN_INDEX,
 314     CONFIGURE_INSTANCE_FUN_INDEX,
 315     MATH_ABS_FUN_INDEX,
 316     MATH_ACOS_FUN_INDEX,
 317     MATH_ASIN_FUN_INDEX,
 318     MATH_ATAN_FUN_INDEX,
 319     MATH_ATAN2_FUN_INDEX,
 320     MATH_CEIL_FUN_INDEX,
 321     MATH_COS_FUN_INDEX,
 322     MATH_EXP_FUN_INDEX,
 323     MATH_FLOOR_FUN_INDEX,
 324     MATH_IMUL_FUN_INDEX,
 325     MATH_LOG_FUN_INDEX,
 326     MATH_MAX_FUN_INDEX,
 327     MATH_MIN_FUN_INDEX,
 328     MATH_POW_FUN_INDEX,
 329     MATH_RANDOM_FUN_INDEX,
 330     MATH_ROUND_FUN_INDEX,
 331     MATH_SIN_FUN_INDEX,
 332     MATH_SQRT_FUN_INDEX,
 333     MATH_TAN_FUN_INDEX,
 334     ARRAY_BUFFER_FUN_INDEX,
 335     UINT8_ARRAY_FUN_INDEX,
 336     INT8_ARRAY_FUN_INDEX,
 337     UINT16_ARRAY_FUN_INDEX,
 338     INT16_ARRAY_FUN_INDEX,
 339     UINT32_ARRAY_FUN_INDEX,
 340     INT32_ARRAY_FUN_INDEX,
 341     FLOAT32_ARRAY_FUN_INDEX,
 342     FLOAT64_ARRAY_FUN_INDEX,
 343     UINT8_CLAMPED_ARRAY_FUN_INDEX,
 344     INT8_ARRAY_EXTERNAL_MAP_INDEX,
 345     UINT8_ARRAY_EXTERNAL_MAP_INDEX,
 346     INT16_ARRAY_EXTERNAL_MAP_INDEX,
 347     UINT16_ARRAY_EXTERNAL_MAP_INDEX,
 348     INT32_ARRAY_EXTERNAL_MAP_INDEX,
 349     UINT32_ARRAY_EXTERNAL_MAP_INDEX,
 350     FLOAT32_ARRAY_EXTERNAL_MAP_INDEX,
 351     FLOAT64_ARRAY_EXTERNAL_MAP_INDEX,
 352     UINT8_CLAMPED_ARRAY_EXTERNAL_MAP_INDEX,
 353     DATA_VIEW_FUN_INDEX,
 354     MESSAGE_LISTENERS_INDEX,
 355     MAKE_MESSAGE_FUN_INDEX,
 356     GET_STACK_TRACE_LINE_INDEX,
 357     CONFIGURE_GLOBAL_INDEX,
 358     FUNCTION_CACHE_INDEX,
 359     JSFUNCTION_RESULT_CACHES_INDEX,
 360     NORMALIZED_MAP_CACHE_INDEX,
 361     RUNTIME_CONTEXT_INDEX,
 362     CALL_AS_FUNCTION_DELEGATE_INDEX,
 363     CALL_AS_CONSTRUCTOR_DELEGATE_INDEX,
 364     SCRIPT_FUNCTION_INDEX,
 365     OPAQUE_REFERENCE_FUNCTION_INDEX,
 366     CONTEXT_EXTENSION_FUNCTION_INDEX,
 367     OUT_OF_MEMORY_INDEX,
 368     EMBEDDER_DATA_INDEX,
 369     ALLOW_CODE_GEN_FROM_STRINGS_INDEX,
 370     ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX,
 371     RUN_MICROTASKS_INDEX,
 372     ENQUEUE_MICROTASK_INDEX,
 373     IS_PROMISE_INDEX,
 374     PROMISE_CREATE_INDEX,
 375     PROMISE_RESOLVE_INDEX,
 376     PROMISE_REJECT_INDEX,
 377     PROMISE_CHAIN_INDEX,
 378     PROMISE_CATCH_INDEX,
 379     PROMISE_THEN_INDEX,
 380     TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX,
 381     DERIVED_HAS_TRAP_INDEX,
 382     DERIVED_GET_TRAP_INDEX,
 383     DERIVED_SET_TRAP_INDEX,
 384     PROXY_ENUMERATE_INDEX,
 385     OBSERVERS_NOTIFY_CHANGE_INDEX,
 386     OBSERVERS_ENQUEUE_SPLICE_INDEX,
 387     OBSERVERS_BEGIN_SPLICE_INDEX,
 388     OBSERVERS_END_SPLICE_INDEX,
 389     NATIVE_OBJECT_OBSERVE_INDEX,
 390     NATIVE_OBJECT_GET_NOTIFIER_INDEX,
 391     NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE,
 392     SLOPPY_GENERATOR_FUNCTION_MAP_INDEX,
 393     STRICT_GENERATOR_FUNCTION_MAP_INDEX,
 394     GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX,
 395     ITERATOR_RESULT_MAP_INDEX,
 396     MAP_ITERATOR_MAP_INDEX,
 397     SET_ITERATOR_MAP_INDEX,
 398     ITERATOR_SYMBOL_INDEX,
 399     UNSCOPABLES_SYMBOL_INDEX,
 400     ARRAY_VALUES_ITERATOR_INDEX,
 401
 402     // Properties from here are treated as weak references by the full GC.
 403     // Scavenge treats them as strong references.
 404     OPTIMIZED_FUNCTIONS_LIST,  // Weak.
 405     OPTIMIZED_CODE_LIST,       // Weak.
 406     DEOPTIMIZED_CODE_LIST,     // Weak.
 407     MAP_CACHE_INDEX,           // Weak.
 408     NEXT_CONTEXT_LINK,         // Weak.
 409
 410     // Total number of slots.
 411     NATIVE_CONTEXT_SLOTS,
 412     FIRST_WEAK_SLOT = OPTIMIZED_FUNCTIONS_LIST
 413   };
 414
 415   // Direct slot access.
 416   JSFunction* closure() { return JSFunction::cast(get(CLOSURE_INDEX)); }
 417   void set_closure(JSFunction* closure) { set(CLOSURE_INDEX, closure); }
 418
 419   Context* previous() {
 420     Object* result = unchecked_previous();
 421     DCHECK(IsBootstrappingOrValidParentContext(result, this));
 422     return reinterpret_cast<Context*>(result);
 423   }
 424   void set_previous(Context* context) { set(PREVIOUS_INDEX, context); }
 425
 426   bool has_extension() { return extension() != NULL; }
 427   Object* extension() { return get(EXTENSION_INDEX); }
 428   void set_extension(Object* object) { set(EXTENSION_INDEX, object); }
 429
 430   JSModule* module() { return JSModule::cast(get(EXTENSION_INDEX)); }
 431   void set_module(JSModule* module) { set(EXTENSION_INDEX, module); }
 432
 433   // Get the context where var declarations will be hoisted to, which
 434   // may be the context itself.
 435   Context* declaration_context();
 436
 437   GlobalObject* global_object() {
 438     Object* result = get(GLOBAL_OBJECT_INDEX);
 439     DCHECK(IsBootstrappingOrGlobalObject(this->GetIsolate(), result));
 440     return reinterpret_cast<GlobalObject*>(result);
 441   }
 442   void set_global_object(GlobalObject* object) {
 443     set(GLOBAL_OBJECT_INDEX, object);
 444   }
 445
 446   // Returns a JSGlobalProxy object or null.
 447   JSObject* global_proxy();
 448   void set_global_proxy(JSObject* global);
 449
 450   // The builtins object.
 451   JSBuiltinsObject* builtins();
 452
 453   // Get the innermost global context by traversing the context chain.
 454   Context* global_context();
 455
 456   // Compute the native context by traversing the context chain.
 457   Context* native_context();
 458
 459   // Predicates for context types.  IsNativeContext is also defined on Object
 460   // because we frequently have to know if arbitrary objects are natives
 461   // contexts.
 462   bool IsNativeContext() {
 463     Map* map = this->map();
 464     return map == map->GetHeap()->native_context_map();
 465   }
 466   bool IsFunctionContext() {
 467     Map* map = this->map();
 468     return map == map->GetHeap()->function_context_map();
 469   }
 470   bool IsCatchContext() {
 471     Map* map = this->map();
 472     return map == map->GetHeap()->catch_context_map();
 473   }
 474   bool IsWithContext() {
 475     Map* map = this->map();
 476     return map == map->GetHeap()->with_context_map();
 477   }
 478   bool IsBlockContext() {
 479     Map* map = this->map();
 480     return map == map->GetHeap()->block_context_map();
 481   }
 482   bool IsModuleContext() {
 483     Map* map = this->map();
 484     return map == map->GetHeap()->module_context_map();
 485   }
 486   bool IsGlobalContext() {
 487     Map* map = this->map();
 488     return map == map->GetHeap()->global_context_map();
 489   }
 490
 491   bool HasSameSecurityTokenAs(Context* that) {
 492     return this->global_object()->native_context()->security_token() ==
 493         that->global_object()->native_context()->security_token();
 494   }
 495
 496   // A native context holds a list of all functions with optimized code.
 497   void AddOptimizedFunction(JSFunction* function);
 498   void RemoveOptimizedFunction(JSFunction* function);
 499   void SetOptimizedFunctionsListHead(Object* head);
 500   Object* OptimizedFunctionsListHead();
 501
 502   // The native context also stores a list of all optimized code and a
 503   // list of all deoptimized code, which are needed by the deoptimizer.
 504   void AddOptimizedCode(Code* code);
 505   void SetOptimizedCodeListHead(Object* head);
 506   Object* OptimizedCodeListHead();
 507   void SetDeoptimizedCodeListHead(Object* head);
 508   Object* DeoptimizedCodeListHead();
 509
 510   Handle<Object> ErrorMessageForCodeGenerationFromStrings();
 511
 512 #define NATIVE_CONTEXT_FIELD_ACCESSORS(index, type, name) \
 513   void  set_##name(type* value) {                         \
 514     DCHECK(IsNativeContext());                            \
 515     set(index, value);                                    \
 516   }                                                       \
 517   bool is_##name(type* value) {                           \
 518     DCHECK(IsNativeContext());                            \
 519     return type::cast(get(index)) == value;               \
 520   }                                                       \
 521   type* name() {                                          \
 522     DCHECK(IsNativeContext());                            \
 523     return type::cast(get(index));                        \
 524   }
 525   NATIVE_CONTEXT_FIELDS(NATIVE_CONTEXT_FIELD_ACCESSORS)
 526 #undef NATIVE_CONTEXT_FIELD_ACCESSORS
 527
 528   // Lookup the slot called name, starting with the current context.
 529   // There are three possibilities:
 530   //
 531   // 1) result->IsContext():
 532   //    The binding was found in a context.  *index is always the
 533   //    non-negative slot index.  *attributes is NONE for var and let
 534   //    declarations, READ_ONLY for const declarations (never ABSENT).
 535   //
 536   // 2) result->IsJSObject():
 537   //    The binding was found as a named property in a context extension
 538   //    object (i.e., was introduced via eval), as a property on the subject
 539   //    of with, or as a property of the global object.  *index is -1 and
 540   //    *attributes is not ABSENT.
 541   //
 542   // 3) result.is_null():
 543   //    There was no binding found, *index is always -1 and *attributes is
 544   //    always ABSENT.
 545   Handle<Object> Lookup(Handle<String> name,
 546                         ContextLookupFlags flags,
 547                         int* index,
 548                         PropertyAttributes* attributes,
 549                         BindingFlags* binding_flags);
 550
 551   // Code generation support.
 552   static int SlotOffset(int index) {
 553     return kHeaderSize + index * kPointerSize - kHeapObjectTag;
 554   }
 555
 556   static int FunctionMapIndex(StrictMode strict_mode, FunctionKind kind) {
 557     if (IsGeneratorFunction(kind)) {
 558       return strict_mode == SLOPPY ? SLOPPY_GENERATOR_FUNCTION_MAP_INDEX
 559                                    : STRICT_GENERATOR_FUNCTION_MAP_INDEX;
 560     }
 561
 562     if (IsArrowFunction(kind) || IsConciseMethod(kind)) {
 563       return strict_mode == SLOPPY
 564                  ? SLOPPY_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX
 565                  : STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX;
 566     }
 567
 568     return strict_mode == SLOPPY ? SLOPPY_FUNCTION_MAP_INDEX
 569                                  : STRICT_FUNCTION_MAP_INDEX;
 570   }
 571
 572   static const int kSize = kHeaderSize + NATIVE_CONTEXT_SLOTS * kPointerSize;
 573
 574   // GC support.
 575   typedef FixedBodyDescriptor<
 576       kHeaderSize, kSize, kSize> ScavengeBodyDescriptor;
 577
 578   typedef FixedBodyDescriptor<
 579       kHeaderSize,
 580       kHeaderSize + FIRST_WEAK_SLOT * kPointerSize,
 581       kSize> MarkCompactBodyDescriptor;
 582
 583  private:
 584   // Unchecked access to the slots.
 585   Object* unchecked_previous() { return get(PREVIOUS_INDEX); }
 586
 587 #ifdef DEBUG
 588   // Bootstrapping-aware type checks.
 589   static bool IsBootstrappingOrValidParentContext(Object* object, Context* kid);
 590   static bool IsBootstrappingOrGlobalObject(Isolate* isolate, Object* object);
 591 #endif
 592
 593   STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize);
 594   STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex);
 595 };
 596
 597 } }  // namespace v8::internal
 598
 599 #endif  // V8_CONTEXTS_H_