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 << 0, 17 FOLLOW_PROTOTYPE_CHAIN = 1 << 1, 18 STOP_AT_DECLARATION_SCOPE = 1 << 2, 19 SKIP_WITH_CONTEXT = 1 << 3, 20 21 DONT_FOLLOW_CHAINS = 0, 22 FOLLOW_CHAINS = FOLLOW_CONTEXT_CHAIN | FOLLOW_PROTOTYPE_CHAIN, 23 LEXICAL_TEST = 24 FOLLOW_CONTEXT_CHAIN | STOP_AT_DECLARATION_SCOPE | SKIP_WITH_CONTEXT, 25 }; 26 27 28 // ES5 10.2 defines lexical environments with mutable and immutable bindings. 29 // Immutable bindings have two states, initialized and uninitialized, and 30 // their state is changed by the InitializeImmutableBinding method. The 31 // BindingFlags enum represents information if a binding has definitely been 32 // initialized. A mutable binding does not need to be checked and thus has 33 // the BindingFlag MUTABLE_IS_INITIALIZED. 34 // 35 // There are two possibilities for immutable bindings 36 // * 'const' declared variables. They are initialized when evaluating the 37 // corresponding declaration statement. They need to be checked for being 38 // initialized and thus get the flag IMMUTABLE_CHECK_INITIALIZED. 39 // * The function name of a named function literal. The binding is immediately 40 // initialized when entering the function and thus does not need to be 41 // checked. it gets the BindingFlag IMMUTABLE_IS_INITIALIZED. 42 // Accessing an uninitialized binding produces the undefined value. 43 // 44 // The harmony proposal for block scoped bindings also introduces the 45 // uninitialized state for mutable bindings. 46 // * A 'let' declared variable. They are initialized when evaluating the 47 // corresponding declaration statement. They need to be checked for being 48 // initialized and thus get the flag MUTABLE_CHECK_INITIALIZED. 49 // * A 'var' declared variable. It is initialized immediately upon creation 50 // and thus doesn't need to be checked. It gets the flag 51 // MUTABLE_IS_INITIALIZED. 52 // * Catch bound variables, function parameters and variables introduced by 53 // function declarations are initialized immediately and do not need to be 54 // checked. Thus they get the flag MUTABLE_IS_INITIALIZED. 55 // Immutable bindings in harmony mode get the _HARMONY flag variants. Accessing 56 // an uninitialized binding produces a reference error. 57 // 58 // In V8 uninitialized bindings are set to the hole value upon creation and set 59 // to a different value upon initialization. 60 enum BindingFlags { 61 MUTABLE_IS_INITIALIZED, 62 MUTABLE_CHECK_INITIALIZED, 63 IMMUTABLE_IS_INITIALIZED, 64 IMMUTABLE_CHECK_INITIALIZED, 65 IMMUTABLE_IS_INITIALIZED_HARMONY, 66 IMMUTABLE_CHECK_INITIALIZED_HARMONY, 67 MISSING_BINDING 68 }; 69 70 71 // Heap-allocated activation contexts. 72 // 73 // Contexts are implemented as FixedArray objects; the Context 74 // class is a convenience interface casted on a FixedArray object. 75 // 76 // Note: Context must have no virtual functions and Context objects 77 // must always be allocated via Heap::AllocateContext() or 78 // Factory::NewContext. 79 80 #define NATIVE_CONTEXT_INTRINSIC_FUNCTIONS(V) \ 81 V(IS_ARRAYLIKE, JSFunction, is_arraylike) \ 82 V(CONCAT_ITERABLE_TO_ARRAY_INDEX, JSFunction, concat_iterable_to_array) \ 83 V(GET_TEMPLATE_CALL_SITE_INDEX, JSFunction, get_template_call_site) \ 84 V(MAKE_RANGE_ERROR_INDEX, JSFunction, make_range_error) \ 85 V(MAKE_TYPE_ERROR_INDEX, JSFunction, make_type_error) \ 86 V(OBJECT_FREEZE, JSFunction, object_freeze) \ 87 V(OBJECT_IS_EXTENSIBLE, JSFunction, object_is_extensible) \ 88 V(OBJECT_IS_FROZEN, JSFunction, object_is_frozen) \ 89 V(OBJECT_IS_SEALED, JSFunction, object_is_sealed) \ 90 V(OBJECT_KEYS, JSFunction, object_keys) \ 91 V(REFLECT_APPLY_INDEX, JSFunction, reflect_apply) \ 92 V(REFLECT_CONSTRUCT_INDEX, JSFunction, reflect_construct) \ 93 V(REFLECT_DEFINE_PROPERTY_INDEX, JSFunction, reflect_define_property) \ 94 V(REFLECT_DELETE_PROPERTY_INDEX, JSFunction, reflect_delete_property) \ 95 V(SPREAD_ARGUMENTS_INDEX, JSFunction, spread_arguments) \ 96 V(SPREAD_ITERABLE_INDEX, JSFunction, spread_iterable) 97 98 99 #define NATIVE_CONTEXT_JS_BUILTINS(V) \ 100 V(CONCAT_ITERABLE_TO_ARRAY_BUILTIN_INDEX, JSFunction, \ 101 concat_iterable_to_array_builtin) 102 103 104 #define NATIVE_CONTEXT_IMPORTED_FIELDS(V) \ 105 V(ARRAY_CONCAT_INDEX, JSFunction, array_concat) \ 106 V(ARRAY_POP_INDEX, JSFunction, array_pop) \ 107 V(ARRAY_PUSH_INDEX, JSFunction, array_push) \ 108 V(ARRAY_SHIFT_INDEX, JSFunction, array_shift) \ 109 V(ARRAY_SPLICE_INDEX, JSFunction, array_splice) \ 110 V(ARRAY_SLICE_INDEX, JSFunction, array_slice) \ 111 V(ARRAY_UNSHIFT_INDEX, JSFunction, array_unshift) \ 112 V(ARRAY_VALUES_ITERATOR_INDEX, JSFunction, array_values_iterator) \ 113 V(DERIVED_GET_TRAP_INDEX, JSFunction, derived_get_trap) \ 114 V(ERROR_FUNCTION_INDEX, JSFunction, error_function) \ 115 V(EVAL_ERROR_FUNCTION_INDEX, JSFunction, eval_error_function) \ 116 V(GET_STACK_TRACE_LINE_INDEX, JSFunction, get_stack_trace_line_fun) \ 117 V(GLOBAL_EVAL_FUN_INDEX, JSFunction, global_eval_fun) \ 118 V(JSON_SERIALIZE_ADAPTER_INDEX, JSFunction, json_serialize_adapter) \ 119 V(MAKE_ERROR_FUNCTION_INDEX, JSFunction, make_error_function) \ 120 V(MAP_DELETE_METHOD_INDEX, JSFunction, map_delete) \ 121 V(MAP_GET_METHOD_INDEX, JSFunction, map_get) \ 122 V(MAP_HAS_METHOD_INDEX, JSFunction, map_has) \ 123 V(MAP_SET_METHOD_INDEX, JSFunction, map_set) \ 124 V(MESSAGE_GET_COLUMN_NUMBER_INDEX, JSFunction, message_get_column_number) \ 125 V(MESSAGE_GET_LINE_NUMBER_INDEX, JSFunction, message_get_line_number) \ 126 V(MESSAGE_GET_SOURCE_LINE_INDEX, JSFunction, message_get_source_line) \ 127 V(NATIVE_OBJECT_GET_NOTIFIER_INDEX, JSFunction, native_object_get_notifier) \ 128 V(NATIVE_OBJECT_NOTIFIER_PERFORM_CHANGE, JSFunction, \ 129 native_object_notifier_perform_change) \ 130 V(NATIVE_OBJECT_OBSERVE_INDEX, JSFunction, native_object_observe) \ 131 V(NO_SIDE_EFFECTS_TO_STRING_FUN_INDEX, JSFunction, \ 132 no_side_effects_to_string_fun) \ 133 V(OBJECT_VALUE_OF, JSFunction, object_value_of) \ 134 V(OBJECT_TO_STRING, JSFunction, object_to_string) \ 135 V(OBSERVERS_BEGIN_SPLICE_INDEX, JSFunction, observers_begin_perform_splice) \ 136 V(OBSERVERS_END_SPLICE_INDEX, JSFunction, observers_end_perform_splice) \ 137 V(OBSERVERS_ENQUEUE_SPLICE_INDEX, JSFunction, observers_enqueue_splice) \ 138 V(OBSERVERS_NOTIFY_CHANGE_INDEX, JSFunction, observers_notify_change) \ 139 V(PROMISE_CATCH_INDEX, JSFunction, promise_catch) \ 140 V(PROMISE_CHAIN_INDEX, JSFunction, promise_chain) \ 141 V(PROMISE_CREATE_INDEX, JSFunction, promise_create) \ 142 V(PROMISE_FUNCTION_INDEX, JSFunction, promise_function) \ 143 V(PROMISE_HAS_USER_DEFINED_REJECT_HANDLER_INDEX, JSFunction, \ 144 promise_has_user_defined_reject_handler) \ 145 V(PROMISE_REJECT_INDEX, JSFunction, promise_reject) \ 146 V(PROMISE_RESOLVE_INDEX, JSFunction, promise_resolve) \ 147 V(PROMISE_THEN_INDEX, JSFunction, promise_then) \ 148 V(PROXY_ENUMERATE_INDEX, JSFunction, proxy_enumerate) \ 149 V(RANGE_ERROR_FUNCTION_INDEX, JSFunction, range_error_function) \ 150 V(REFERENCE_ERROR_FUNCTION_INDEX, JSFunction, reference_error_function) \ 151 V(SET_ADD_METHOD_INDEX, JSFunction, set_add) \ 152 V(SET_DELETE_METHOD_INDEX, JSFunction, set_delete) \ 153 V(SET_HAS_METHOD_INDEX, JSFunction, set_has) \ 154 V(STACK_OVERFLOW_BOILERPLATE_INDEX, JSObject, stack_overflow_boilerplate) \ 155 V(SYNTAX_ERROR_FUNCTION_INDEX, JSFunction, syntax_error_function) \ 156 V(TYPE_ERROR_FUNCTION_INDEX, JSFunction, type_error_function) \ 157 V(URI_ERROR_FUNCTION_INDEX, JSFunction, uri_error_function) \ 158 NATIVE_CONTEXT_JS_BUILTINS(V) 159 160 #define NATIVE_CONTEXT_FIELDS(V) \ 161 V(GLOBAL_PROXY_INDEX, JSObject, global_proxy_object) \ 162 V(EMBEDDER_DATA_INDEX, FixedArray, embedder_data) \ 163 /* Below is alpha-sorted */ \ 164 V(ALLOW_CODE_GEN_FROM_STRINGS_INDEX, Object, allow_code_gen_from_strings) \ 165 V(ARRAY_BUFFER_FUN_INDEX, JSFunction, array_buffer_fun) \ 166 V(ARRAY_BUFFER_MAP_INDEX, Map, array_buffer_map) \ 167 V(ARRAY_FUNCTION_INDEX, JSFunction, array_function) \ 168 V(BOOL16X8_FUNCTION_INDEX, JSFunction, bool16x8_function) \ 169 V(BOOL32X4_FUNCTION_INDEX, JSFunction, bool32x4_function) \ 170 V(BOOL8X16_FUNCTION_INDEX, JSFunction, bool8x16_function) \ 171 V(BOOLEAN_FUNCTION_INDEX, JSFunction, boolean_function) \ 172 V(BOUND_FUNCTION_WITH_CONSTRUCTOR_MAP_INDEX, Map, \ 173 bound_function_with_constructor_map) \ 174 V(BOUND_FUNCTION_WITHOUT_CONSTRUCTOR_MAP_INDEX, Map, \ 175 bound_function_without_constructor_map) \ 176 V(CALL_AS_CONSTRUCTOR_DELEGATE_INDEX, JSFunction, \ 177 call_as_constructor_delegate) \ 178 V(CALL_AS_FUNCTION_DELEGATE_INDEX, JSFunction, call_as_function_delegate) \ 179 V(CONTEXT_EXTENSION_FUNCTION_INDEX, JSFunction, context_extension_function) \ 180 V(DATA_VIEW_FUN_INDEX, JSFunction, data_view_fun) \ 181 V(DATE_FUNCTION_INDEX, JSFunction, date_function) \ 182 V(ERROR_MESSAGE_FOR_CODE_GEN_FROM_STRINGS_INDEX, Object, \ 183 error_message_for_code_gen_from_strings) \ 184 V(ERRORS_THROWN_INDEX, Smi, errors_thrown) \ 185 V(EXTRAS_EXPORTS_OBJECT_INDEX, JSObject, extras_binding_object) \ 186 V(EXTRAS_UTILS_OBJECT_INDEX, JSObject, extras_utils_object) \ 187 V(FAST_ALIASED_ARGUMENTS_MAP_INDEX, Map, fast_aliased_arguments_map) \ 188 V(FLOAT32_ARRAY_FUN_INDEX, JSFunction, float32_array_fun) \ 189 V(FLOAT32X4_FUNCTION_INDEX, JSFunction, float32x4_function) \ 190 V(FLOAT64_ARRAY_FUN_INDEX, JSFunction, float64_array_fun) \ 191 V(FUNCTION_CACHE_INDEX, ObjectHashTable, function_cache) \ 192 V(FUNCTION_FUNCTION_INDEX, JSFunction, function_function) \ 193 V(GENERATOR_FUNCTION_FUNCTION_INDEX, JSFunction, \ 194 generator_function_function) \ 195 V(GENERATOR_OBJECT_PROTOTYPE_MAP_INDEX, Map, generator_object_prototype_map) \ 196 V(INITIAL_ARRAY_PROTOTYPE_INDEX, JSObject, initial_array_prototype) \ 197 V(INITIAL_OBJECT_PROTOTYPE_INDEX, JSObject, initial_object_prototype) \ 198 V(INT16_ARRAY_FUN_INDEX, JSFunction, int16_array_fun) \ 199 V(INT16X8_FUNCTION_INDEX, JSFunction, int16x8_function) \ 200 V(INT32_ARRAY_FUN_INDEX, JSFunction, int32_array_fun) \ 201 V(INT32X4_FUNCTION_INDEX, JSFunction, int32x4_function) \ 202 V(INT8_ARRAY_FUN_INDEX, JSFunction, int8_array_fun) \ 203 V(INT8X16_FUNCTION_INDEX, JSFunction, int8x16_function) \ 204 V(INTERNAL_ARRAY_FUNCTION_INDEX, JSFunction, internal_array_function) \ 205 V(ITERATOR_RESULT_MAP_INDEX, Map, iterator_result_map) \ 206 V(JS_ARRAY_FAST_SMI_ELEMENTS_MAP_INDEX, Map, \ 207 js_array_fast_smi_elements_map_index) \ 208 V(JS_ARRAY_FAST_HOLEY_SMI_ELEMENTS_MAP_INDEX, Map, \ 209 js_array_fast_holey_smi_elements_map_index) \ 210 V(JS_ARRAY_FAST_ELEMENTS_MAP_INDEX, Map, js_array_fast_elements_map_index) \ 211 V(JS_ARRAY_FAST_HOLEY_ELEMENTS_MAP_INDEX, Map, \ 212 js_array_fast_holey_elements_map_index) \ 213 V(JS_ARRAY_FAST_DOUBLE_ELEMENTS_MAP_INDEX, Map, \ 214 js_array_fast_double_elements_map_index) \ 215 V(JS_ARRAY_FAST_HOLEY_DOUBLE_ELEMENTS_MAP_INDEX, Map, \ 216 js_array_fast_holey_double_elements_map_index) \ 217 V(JS_ARRAY_FAST_SMI_ELEMENTS_STRONG_MAP_INDEX, Map, \ 218 js_array_fast_smi_elements_strong_map_index) \ 219 V(JS_ARRAY_FAST_HOLEY_SMI_ELEMENTS_STRONG_MAP_INDEX, Map, \ 220 js_array_fast_holey_smi_elements_strong_map_index) \ 221 V(JS_ARRAY_FAST_ELEMENTS_STRONG_MAP_INDEX, Map, \ 222 js_array_fast_elements_strong_map_index) \ 223 V(JS_ARRAY_FAST_HOLEY_ELEMENTS_STRONG_MAP_INDEX, Map, \ 224 js_array_fast_holey_elements_strong_map_index) \ 225 V(JS_ARRAY_FAST_DOUBLE_ELEMENTS_STRONG_MAP_INDEX, Map, \ 226 js_array_fast_double_elements_strong_map_index) \ 227 V(JS_ARRAY_FAST_HOLEY_DOUBLE_ELEMENTS_STRONG_MAP_INDEX, Map, \ 228 js_array_fast_holey_double_elements_strong_map_index) \ 229 V(JS_MAP_FUN_INDEX, JSFunction, js_map_fun) \ 230 V(JS_MAP_MAP_INDEX, Map, js_map_map) \ 231 V(JS_OBJECT_STRONG_MAP_INDEX, Map, js_object_strong_map) \ 232 V(JS_SET_FUN_INDEX, JSFunction, js_set_fun) \ 233 V(JS_SET_MAP_INDEX, Map, js_set_map) \ 234 V(JS_WEAK_MAP_FUN_INDEX, JSFunction, js_weak_map_fun) \ 235 V(JS_WEAK_SET_FUN_INDEX, JSFunction, js_weak_set_fun) \ 236 V(MAP_CACHE_INDEX, Object, map_cache) \ 237 V(MAP_ITERATOR_MAP_INDEX, Map, map_iterator_map) \ 238 V(STRING_ITERATOR_MAP_INDEX, Map, string_iterator_map) \ 239 V(MESSAGE_LISTENERS_INDEX, JSObject, message_listeners) \ 240 V(NATIVES_UTILS_OBJECT_INDEX, Object, natives_utils_object) \ 241 V(NORMALIZED_MAP_CACHE_INDEX, Object, normalized_map_cache) \ 242 V(NUMBER_FUNCTION_INDEX, JSFunction, number_function) \ 243 V(OBJECT_FUNCTION_INDEX, JSFunction, object_function) \ 244 V(OBJECT_FUNCTION_PROTOTYPE_MAP_INDEX, Map, object_function_prototype_map) \ 245 V(OPAQUE_REFERENCE_FUNCTION_INDEX, JSFunction, opaque_reference_function) \ 246 V(PROXY_CALLABLE_MAP_INDEX, Map, proxy_callable_map) \ 247 V(PROXY_CONSTRUCTOR_MAP_INDEX, Map, proxy_constructor_map) \ 248 V(PROXY_FUNCTION_INDEX, JSFunction, proxy_function) \ 249 V(PROXY_FUNCTION_MAP_INDEX, Map, proxy_function_map) \ 250 V(PROXY_MAP_INDEX, Map, proxy_map) \ 251 V(REGEXP_FUNCTION_INDEX, JSFunction, regexp_function) \ 252 V(REGEXP_RESULT_MAP_INDEX, Map, regexp_result_map) \ 253 V(SCRIPT_CONTEXT_TABLE_INDEX, ScriptContextTable, script_context_table) \ 254 V(SCRIPT_FUNCTION_INDEX, JSFunction, script_function) \ 255 V(SECURITY_TOKEN_INDEX, Object, security_token) \ 256 V(SELF_WEAK_CELL_INDEX, WeakCell, self_weak_cell) \ 257 V(SET_ITERATOR_MAP_INDEX, Map, set_iterator_map) \ 258 V(SHARED_ARRAY_BUFFER_FUN_INDEX, JSFunction, shared_array_buffer_fun) \ 259 V(SLOPPY_ARGUMENTS_MAP_INDEX, Map, sloppy_arguments_map) \ 260 V(SLOPPY_FUNCTION_MAP_INDEX, Map, sloppy_function_map) \ 261 V(SLOPPY_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX, Map, \ 262 sloppy_function_without_prototype_map) \ 263 V(SLOPPY_FUNCTION_WITH_READONLY_PROTOTYPE_MAP_INDEX, Map, \ 264 sloppy_function_with_readonly_prototype_map) \ 265 V(WASM_FUNCTION_MAP_INDEX, Map, wasm_function_map) \ 266 V(SLOPPY_GENERATOR_FUNCTION_MAP_INDEX, Map, sloppy_generator_function_map) \ 267 V(SLOW_ALIASED_ARGUMENTS_MAP_INDEX, Map, slow_aliased_arguments_map) \ 268 V(STRICT_ARGUMENTS_MAP_INDEX, Map, strict_arguments_map) \ 269 V(STRICT_FUNCTION_MAP_INDEX, Map, strict_function_map) \ 270 V(STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX, Map, \ 271 strict_function_without_prototype_map) \ 272 V(STRICT_GENERATOR_FUNCTION_MAP_INDEX, Map, strict_generator_function_map) \ 273 V(STRING_FUNCTION_INDEX, JSFunction, string_function) \ 274 V(STRING_FUNCTION_PROTOTYPE_MAP_INDEX, Map, string_function_prototype_map) \ 275 V(STRONG_CONSTRUCTOR_MAP_INDEX, Map, strong_constructor_map) \ 276 V(STRONG_FUNCTION_MAP_INDEX, Map, strong_function_map) \ 277 V(STRONG_GENERATOR_FUNCTION_MAP_INDEX, Map, strong_generator_function_map) \ 278 V(STRONG_MAP_CACHE_INDEX, Object, strong_map_cache) \ 279 V(SYMBOL_FUNCTION_INDEX, JSFunction, symbol_function) \ 280 V(UINT16_ARRAY_FUN_INDEX, JSFunction, uint16_array_fun) \ 281 V(UINT16X8_FUNCTION_INDEX, JSFunction, uint16x8_function) \ 282 V(UINT32_ARRAY_FUN_INDEX, JSFunction, uint32_array_fun) \ 283 V(UINT32X4_FUNCTION_INDEX, JSFunction, uint32x4_function) \ 284 V(UINT8_ARRAY_FUN_INDEX, JSFunction, uint8_array_fun) \ 285 V(UINT8_CLAMPED_ARRAY_FUN_INDEX, JSFunction, uint8_clamped_array_fun) \ 286 V(UINT8X16_FUNCTION_INDEX, JSFunction, uint8x16_function) \ 287 NATIVE_CONTEXT_INTRINSIC_FUNCTIONS(V) \ 288 NATIVE_CONTEXT_IMPORTED_FIELDS(V) 289 290 // A table of all script contexts. Every loaded top-level script with top-level 291 // lexical declarations contributes its ScriptContext into this table. 292 // 293 // The table is a fixed array, its first slot is the current used count and 294 // the subsequent slots 1..used contain ScriptContexts. 295 class ScriptContextTable : public FixedArray { 296 public: 297 // Conversions. 298 static inline ScriptContextTable* cast(Object* context); 299 300 struct LookupResult { 301 int context_index; 302 int slot_index; 303 VariableMode mode; 304 InitializationFlag init_flag; 305 MaybeAssignedFlag maybe_assigned_flag; 306 }; 307 308 inline int used() const; 309 inline void set_used(int used); 310 311 static inline Handle<Context> GetContext(Handle<ScriptContextTable> table, 312 int i); 313 314 // Lookup a variable `name` in a ScriptContextTable. 315 // If it returns true, the variable is found and `result` contains 316 // valid information about its location. 317 // If it returns false, `result` is untouched. 318 MUST_USE_RESULT 319 static bool Lookup(Handle<ScriptContextTable> table, Handle<String> name, 320 LookupResult* result); 321 322 MUST_USE_RESULT 323 static Handle<ScriptContextTable> Extend(Handle<ScriptContextTable> table, 324 Handle<Context> script_context); 325 326 static int GetContextOffset(int context_index) { 327 return kFirstContextOffset + context_index * kPointerSize; 328 } 329 330 private: 331 static const int kUsedSlot = 0; 332 static const int kFirstContextSlot = kUsedSlot + 1; 333 static const int kFirstContextOffset = 334 FixedArray::kHeaderSize + kFirstContextSlot * kPointerSize; 335 336 DISALLOW_IMPLICIT_CONSTRUCTORS(ScriptContextTable); 337 }; 338 339 // JSFunctions are pairs (context, function code), sometimes also called 340 // closures. A Context object is used to represent function contexts and 341 // dynamically pushed 'with' contexts (or 'scopes' in ECMA-262 speak). 342 // 343 // At runtime, the contexts build a stack in parallel to the execution 344 // stack, with the top-most context being the current context. All contexts 345 // have the following slots: 346 // 347 // [ closure ] This is the current function. It is the same for all 348 // contexts inside a function. It provides access to the 349 // incoming context (i.e., the outer context, which may 350 // or may not become the current function's context), and 351 // it provides access to the functions code and thus it's 352 // scope information, which in turn contains the names of 353 // statically allocated context slots. The names are needed 354 // for dynamic lookups in the presence of 'with' or 'eval'. 355 // 356 // [ previous ] A pointer to the previous context. It is NULL for 357 // function contexts, and non-NULL for 'with' contexts. 358 // Used to implement the 'with' statement. 359 // 360 // [ extension ] A pointer to an extension JSObject, or "the hole". Used to 361 // implement 'with' statements and dynamic declarations 362 // (through 'eval'). The object in a 'with' statement is 363 // stored in the extension slot of a 'with' context. 364 // Dynamically declared variables/functions are also added 365 // to lazily allocated extension object. Context::Lookup 366 // searches the extension object for properties. 367 // For script and block contexts, contains the respective 368 // ScopeInfo. For block contexts representing sloppy declaration 369 // block scopes, it may also be a struct being a 370 // SloppyBlockWithEvalContextExtension, pairing the ScopeInfo 371 // with an extension object. 372 // For module contexts, points back to the respective JSModule. 373 // 374 // [ global_object ] A pointer to the global object. Provided for quick 375 // access to the global object from inside the code (since 376 // we always have a context pointer). 377 // 378 // In addition, function contexts may have statically allocated context slots 379 // to store local variables/functions that are accessed from inner functions 380 // (via static context addresses) or through 'eval' (dynamic context lookups). 381 // The native context contains additional slots for fast access to native 382 // properties. 383 // 384 // Finally, with Harmony scoping, the JSFunction representing a top level 385 // script will have the ScriptContext rather than a FunctionContext. 386 // Script contexts from all top-level scripts are gathered in 387 // ScriptContextTable. 388 389 class Context: public FixedArray { 390 public: 391 // Conversions. 392 static inline Context* cast(Object* context); 393 394 // The default context slot layout; indices are FixedArray slot indices. 395 enum { 396 // These slots are in all contexts. 397 CLOSURE_INDEX, 398 PREVIOUS_INDEX, 399 // The extension slot is used for either the global object (in native 400 // contexts), eval extension object (function contexts), subject of with 401 // (with contexts), or the variable name (catch contexts), the serialized 402 // scope info (block contexts), or the module instance (module contexts). 403 EXTENSION_INDEX, 404 NATIVE_CONTEXT_INDEX, 405 406 // These slots are only in native contexts. 407 #define NATIVE_CONTEXT_SLOT(index, type, name) index, 408 NATIVE_CONTEXT_FIELDS(NATIVE_CONTEXT_SLOT) 409 #undef NATIVE_CONTEXT_SLOT 410 411 // Properties from here are treated as weak references by the full GC. 412 // Scavenge treats them as strong references. 413 OPTIMIZED_FUNCTIONS_LIST, // Weak. 414 OPTIMIZED_CODE_LIST, // Weak. 415 DEOPTIMIZED_CODE_LIST, // Weak. 416 NEXT_CONTEXT_LINK, // Weak. 417 418 // Total number of slots. 419 NATIVE_CONTEXT_SLOTS, 420 FIRST_WEAK_SLOT = OPTIMIZED_FUNCTIONS_LIST, 421 FIRST_JS_ARRAY_MAP_SLOT = JS_ARRAY_FAST_SMI_ELEMENTS_MAP_INDEX, 422 FIRST_JS_ARRAY_STRONG_MAP_SLOT = 423 JS_ARRAY_FAST_SMI_ELEMENTS_STRONG_MAP_INDEX, 424 425 MIN_CONTEXT_SLOTS = GLOBAL_PROXY_INDEX, 426 // This slot holds the thrown value in catch contexts. 427 THROWN_OBJECT_INDEX = MIN_CONTEXT_SLOTS, 428 }; 429 430 void IncrementErrorsThrown(); 431 int GetErrorsThrown(); 432 433 // Direct slot access. 434 inline JSFunction* closure(); 435 inline void set_closure(JSFunction* closure); 436 437 inline Context* previous(); 438 inline void set_previous(Context* context); 439 440 inline bool has_extension(); 441 inline HeapObject* extension(); 442 inline void set_extension(HeapObject* object); 443 JSObject* extension_object(); 444 JSReceiver* extension_receiver(); 445 ScopeInfo* scope_info(); 446 String* catch_name(); 447 448 inline JSModule* module(); 449 inline void set_module(JSModule* module); 450 451 // Get the context where var declarations will be hoisted to, which 452 // may be the context itself. 453 Context* declaration_context(); 454 bool is_declaration_context(); 455 456 // Returns a JSGlobalProxy object or null. 457 JSObject* global_proxy(); 458 void set_global_proxy(JSObject* global); 459 460 // Get the JSGlobalObject object. 461 JSGlobalObject* global_object(); 462 463 // Get the script context by traversing the context chain. 464 Context* script_context(); 465 466 // Compute the native context. 467 inline Context* native_context(); 468 inline void set_native_context(Context* context); 469 470 // Predicates for context types. IsNativeContext is also defined on Object 471 // because we frequently have to know if arbitrary objects are natives 472 // contexts. 473 inline bool IsNativeContext(); 474 inline bool IsFunctionContext(); 475 inline bool IsCatchContext(); 476 inline bool IsWithContext(); 477 inline bool IsBlockContext(); 478 inline bool IsModuleContext(); 479 inline bool IsScriptContext(); 480 481 inline bool HasSameSecurityTokenAs(Context* that); 482 483 // Initializes global variable bindings in given script context. 484 void InitializeGlobalSlots(); 485 486 // A native context holds a list of all functions with optimized code. 487 void AddOptimizedFunction(JSFunction* function); 488 void RemoveOptimizedFunction(JSFunction* function); 489 void SetOptimizedFunctionsListHead(Object* head); 490 Object* OptimizedFunctionsListHead(); 491 492 // The native context also stores a list of all optimized code and a 493 // list of all deoptimized code, which are needed by the deoptimizer. 494 void AddOptimizedCode(Code* code); 495 void SetOptimizedCodeListHead(Object* head); 496 Object* OptimizedCodeListHead(); 497 void SetDeoptimizedCodeListHead(Object* head); 498 Object* DeoptimizedCodeListHead(); 499 500 Handle<Object> ErrorMessageForCodeGenerationFromStrings(); 501 502 static int ImportedFieldIndexForName(Handle<String> name); 503 static int IntrinsicIndexForName(Handle<String> name); 504 505 static bool IsJSBuiltin(Handle<Context> native_context, 506 Handle<JSFunction> function); 507 508 #define NATIVE_CONTEXT_FIELD_ACCESSORS(index, type, name) \ 509 inline void set_##name(type* value); \ 510 inline bool is_##name(type* value); \ 511 inline type* name(); 512 NATIVE_CONTEXT_FIELDS(NATIVE_CONTEXT_FIELD_ACCESSORS) 513 #undef NATIVE_CONTEXT_FIELD_ACCESSORS 514 515 // Lookup the slot called name, starting with the current context. 516 // There are three possibilities: 517 // 518 // 1) result->IsContext(): 519 // The binding was found in a context. *index is always the 520 // non-negative slot index. *attributes is NONE for var and let 521 // declarations, READ_ONLY for const declarations (never ABSENT). 522 // 523 // 2) result->IsJSObject(): 524 // The binding was found as a named property in a context extension 525 // object (i.e., was introduced via eval), as a property on the subject 526 // of with, or as a property of the global object. *index is -1 and 527 // *attributes is not ABSENT. 528 // 529 // 3) result.is_null(): 530 // There was no binding found, *index is always -1 and *attributes is 531 // always ABSENT. 532 Handle<Object> Lookup(Handle<String> name, 533 ContextLookupFlags flags, 534 int* index, 535 PropertyAttributes* attributes, 536 BindingFlags* binding_flags); 537 538 // Code generation support. 539 static int SlotOffset(int index) { 540 return kHeaderSize + index * kPointerSize - kHeapObjectTag; 541 } 542 543 static int FunctionMapIndex(LanguageMode language_mode, FunctionKind kind) { 544 if (IsGeneratorFunction(kind)) { 545 return is_strong(language_mode) ? STRONG_GENERATOR_FUNCTION_MAP_INDEX : 546 is_strict(language_mode) ? STRICT_GENERATOR_FUNCTION_MAP_INDEX 547 : SLOPPY_GENERATOR_FUNCTION_MAP_INDEX; 548 } 549 550 if (IsClassConstructor(kind)) { 551 // Use strict function map (no own "caller" / "arguments") 552 return is_strong(language_mode) ? STRONG_CONSTRUCTOR_MAP_INDEX 553 : STRICT_FUNCTION_MAP_INDEX; 554 } 555 556 if (IsArrowFunction(kind) || IsConciseMethod(kind) || 557 IsAccessorFunction(kind)) { 558 return is_strong(language_mode) 559 ? STRONG_FUNCTION_MAP_INDEX 560 : STRICT_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX; 561 } 562 563 return is_strong(language_mode) ? STRONG_FUNCTION_MAP_INDEX : 564 is_strict(language_mode) ? STRICT_FUNCTION_MAP_INDEX 565 : SLOPPY_FUNCTION_MAP_INDEX; 566 } 567 568 static int ArrayMapIndex(ElementsKind elements_kind, 569 Strength strength = Strength::WEAK) { 570 DCHECK(IsFastElementsKind(elements_kind)); 571 return elements_kind + (is_strong(strength) ? FIRST_JS_ARRAY_STRONG_MAP_SLOT 572 : FIRST_JS_ARRAY_MAP_SLOT); 573 } 574 575 static const int kSize = kHeaderSize + NATIVE_CONTEXT_SLOTS * kPointerSize; 576 static const int kNotFound = -1; 577 578 // GC support. 579 typedef FixedBodyDescriptor< 580 kHeaderSize, kSize, kSize> ScavengeBodyDescriptor; 581 582 typedef FixedBodyDescriptor< 583 kHeaderSize, 584 kHeaderSize + FIRST_WEAK_SLOT * kPointerSize, 585 kSize> MarkCompactBodyDescriptor; 586 587 private: 588 #ifdef DEBUG 589 // Bootstrapping-aware type checks. 590 static bool IsBootstrappingOrNativeContext(Isolate* isolate, Object* object); 591 static bool IsBootstrappingOrValidParentContext(Object* object, Context* kid); 592 #endif 593 594 STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize); 595 STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex); 596 }; 597 598 } // namespace internal 599 } // namespace v8 600 601 #endif // V8_CONTEXTS_H_ 602
