1 // Copyright 2012 the V8 project authors. All rights reserved.
2 // Redistribution and use in source and binary forms, with or without
3 // modification, are permitted provided that the following conditions are
6 // * Redistributions of source code must retain the above copyright
7 // notice, this list of conditions and the following disclaimer.
8 // * Redistributions in binary form must reproduce the above
9 // copyright notice, this list of conditions and the following
10 // disclaimer in the documentation and/or other materials provided
11 // with the distribution.
12 // * Neither the name of Google Inc. nor the names of its
13 // contributors may be used to endorse or promote products derived
14 // from this software without specific prior written permission.
16 // THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
17 // "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
18 // LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
19 // A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
20 // OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
21 // SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
22 // LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
23 // DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
24 // THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
25 // (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
26 // OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 #ifndef V8_CONTEXTS_H_
29 #define V8_CONTEXTS_H_
38 enum ContextLookupFlags {
39 FOLLOW_CONTEXT_CHAIN = 1,
40 FOLLOW_PROTOTYPE_CHAIN = 2,
42 DONT_FOLLOW_CHAINS = 0,
43 FOLLOW_CHAINS = FOLLOW_CONTEXT_CHAIN | FOLLOW_PROTOTYPE_CHAIN
47 // ES5 10.2 defines lexical environments with mutable and immutable bindings.
48 // Immutable bindings have two states, initialized and uninitialized, and
49 // their state is changed by the InitializeImmutableBinding method. The
50 // BindingFlags enum represents information if a binding has definitely been
51 // initialized. A mutable binding does not need to be checked and thus has
52 // the BindingFlag MUTABLE_IS_INITIALIZED.
54 // There are two possibilities for immutable bindings
55 // * 'const' declared variables. They are initialized when evaluating the
56 // corresponding declaration statement. They need to be checked for being
57 // initialized and thus get the flag IMMUTABLE_CHECK_INITIALIZED.
58 // * The function name of a named function literal. The binding is immediately
59 // initialized when entering the function and thus does not need to be
60 // checked. it gets the BindingFlag IMMUTABLE_IS_INITIALIZED.
61 // Accessing an uninitialized binding produces the undefined value.
63 // The harmony proposal for block scoped bindings also introduces the
64 // uninitialized state for mutable bindings.
65 // * A 'let' declared variable. They are initialized when evaluating the
66 // corresponding declaration statement. They need to be checked for being
67 // initialized and thus get the flag MUTABLE_CHECK_INITIALIZED.
68 // * A 'var' declared variable. It is initialized immediately upon creation
69 // and thus doesn't need to be checked. It gets the flag
70 // MUTABLE_IS_INITIALIZED.
71 // * Catch bound variables, function parameters and variables introduced by
72 // function declarations are initialized immediately and do not need to be
73 // checked. Thus they get the flag MUTABLE_IS_INITIALIZED.
74 // Immutable bindings in harmony mode get the _HARMONY flag variants. Accessing
75 // an uninitialized binding produces a reference error.
77 // In V8 uninitialized bindings are set to the hole value upon creation and set
78 // to a different value upon initialization.
80 MUTABLE_IS_INITIALIZED,
81 MUTABLE_CHECK_INITIALIZED,
82 IMMUTABLE_IS_INITIALIZED,
83 IMMUTABLE_CHECK_INITIALIZED,
84 IMMUTABLE_IS_INITIALIZED_HARMONY,
85 IMMUTABLE_CHECK_INITIALIZED_HARMONY,
90 // Heap-allocated activation contexts.
92 // Contexts are implemented as FixedArray objects; the Context
93 // class is a convenience interface casted on a FixedArray object.
95 // Note: Context must have no virtual functions and Context objects
96 // must always be allocated via Heap::AllocateContext() or
97 // Factory::NewContext.
99 #define GLOBAL_CONTEXT_FIELDS(V) \
100 V(GLOBAL_PROXY_INDEX, JSObject, global_proxy_object) \
101 V(SECURITY_TOKEN_INDEX, Object, security_token) \
102 V(BOOLEAN_FUNCTION_INDEX, JSFunction, boolean_function) \
103 V(NUMBER_FUNCTION_INDEX, JSFunction, number_function) \
104 V(STRING_FUNCTION_INDEX, JSFunction, string_function) \
105 V(STRING_FUNCTION_PROTOTYPE_MAP_INDEX, Map, string_function_prototype_map) \
106 V(OBJECT_FUNCTION_INDEX, JSFunction, object_function) \
107 V(INTERNAL_ARRAY_FUNCTION_INDEX, JSFunction, internal_array_function) \
108 V(ARRAY_FUNCTION_INDEX, JSFunction, array_function) \
109 V(SMI_JS_ARRAY_MAP_INDEX, Object, smi_js_array_map) \
110 V(DOUBLE_JS_ARRAY_MAP_INDEX, Object, double_js_array_map) \
111 V(OBJECT_JS_ARRAY_MAP_INDEX, Object, object_js_array_map) \
112 V(DATE_FUNCTION_INDEX, JSFunction, date_function) \
113 V(JSON_OBJECT_INDEX, JSObject, json_object) \
114 V(REGEXP_FUNCTION_INDEX, JSFunction, regexp_function) \
115 V(INITIAL_OBJECT_PROTOTYPE_INDEX, JSObject, initial_object_prototype) \
116 V(CREATE_DATE_FUN_INDEX, JSFunction, create_date_fun) \
117 V(TO_NUMBER_FUN_INDEX, JSFunction, to_number_fun) \
118 V(TO_STRING_FUN_INDEX, JSFunction, to_string_fun) \
119 V(TO_DETAIL_STRING_FUN_INDEX, JSFunction, to_detail_string_fun) \
120 V(TO_OBJECT_FUN_INDEX, JSFunction, to_object_fun) \
121 V(TO_INTEGER_FUN_INDEX, JSFunction, to_integer_fun) \
122 V(TO_UINT32_FUN_INDEX, JSFunction, to_uint32_fun) \
123 V(TO_INT32_FUN_INDEX, JSFunction, to_int32_fun) \
124 V(GLOBAL_EVAL_FUN_INDEX, JSFunction, global_eval_fun) \
125 V(INSTANTIATE_FUN_INDEX, JSFunction, instantiate_fun) \
126 V(CONFIGURE_INSTANCE_FUN_INDEX, JSFunction, configure_instance_fun) \
127 V(FUNCTION_MAP_INDEX, Map, function_map) \
128 V(STRICT_MODE_FUNCTION_MAP_INDEX, Map, strict_mode_function_map) \
129 V(FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX, Map, function_without_prototype_map) \
130 V(STRICT_MODE_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX, Map, \
131 strict_mode_function_without_prototype_map) \
132 V(FUNCTION_INSTANCE_MAP_INDEX, Map, function_instance_map) \
133 V(STRICT_MODE_FUNCTION_INSTANCE_MAP_INDEX, Map, \
134 strict_mode_function_instance_map) \
135 V(REGEXP_RESULT_MAP_INDEX, Map, regexp_result_map)\
136 V(ARGUMENTS_BOILERPLATE_INDEX, JSObject, arguments_boilerplate) \
137 V(ALIASED_ARGUMENTS_BOILERPLATE_INDEX, JSObject, \
138 aliased_arguments_boilerplate) \
139 V(STRICT_MODE_ARGUMENTS_BOILERPLATE_INDEX, JSObject, \
140 strict_mode_arguments_boilerplate) \
141 V(MESSAGE_LISTENERS_INDEX, JSObject, message_listeners) \
142 V(MAKE_MESSAGE_FUN_INDEX, JSFunction, make_message_fun) \
143 V(GET_STACK_TRACE_LINE_INDEX, JSFunction, get_stack_trace_line_fun) \
144 V(CONFIGURE_GLOBAL_INDEX, JSFunction, configure_global_fun) \
145 V(FUNCTION_CACHE_INDEX, JSObject, function_cache) \
146 V(JSFUNCTION_RESULT_CACHES_INDEX, FixedArray, jsfunction_result_caches) \
147 V(NORMALIZED_MAP_CACHE_INDEX, NormalizedMapCache, normalized_map_cache) \
148 V(RUNTIME_CONTEXT_INDEX, Context, runtime_context) \
149 V(CALL_AS_FUNCTION_DELEGATE_INDEX, JSFunction, call_as_function_delegate) \
150 V(CALL_AS_CONSTRUCTOR_DELEGATE_INDEX, JSFunction, \
151 call_as_constructor_delegate) \
152 V(SCRIPT_FUNCTION_INDEX, JSFunction, script_function) \
153 V(OPAQUE_REFERENCE_FUNCTION_INDEX, JSFunction, opaque_reference_function) \
154 V(CONTEXT_EXTENSION_FUNCTION_INDEX, JSFunction, context_extension_function) \
155 V(OUT_OF_MEMORY_INDEX, Object, out_of_memory) \
156 V(MAP_CACHE_INDEX, Object, map_cache) \
157 V(CONTEXT_DATA_INDEX, Object, data) \
158 V(ALLOW_CODE_GEN_FROM_STRINGS_INDEX, Object, allow_code_gen_from_strings) \
159 V(TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX, JSFunction, \
160 to_complete_property_descriptor) \
161 V(DERIVED_HAS_TRAP_INDEX, JSFunction, derived_has_trap) \
162 V(DERIVED_GET_TRAP_INDEX, JSFunction, derived_get_trap) \
163 V(DERIVED_SET_TRAP_INDEX, JSFunction, derived_set_trap) \
164 V(PROXY_ENUMERATE, JSFunction, proxy_enumerate) \
165 V(RANDOM_SEED_INDEX, ByteArray, random_seed)
167 // JSFunctions are pairs (context, function code), sometimes also called
168 // closures. A Context object is used to represent function contexts and
169 // dynamically pushed 'with' contexts (or 'scopes' in ECMA-262 speak).
171 // At runtime, the contexts build a stack in parallel to the execution
172 // stack, with the top-most context being the current context. All contexts
173 // have the following slots:
175 // [ closure ] This is the current function. It is the same for all
176 // contexts inside a function. It provides access to the
177 // incoming context (i.e., the outer context, which may
178 // or may not become the current function's context), and
179 // it provides access to the functions code and thus it's
180 // scope information, which in turn contains the names of
181 // statically allocated context slots. The names are needed
182 // for dynamic lookups in the presence of 'with' or 'eval'.
184 // [ previous ] A pointer to the previous context. It is NULL for
185 // function contexts, and non-NULL for 'with' contexts.
186 // Used to implement the 'with' statement.
188 // [ extension ] A pointer to an extension JSObject, or NULL. Used to
189 // implement 'with' statements and dynamic declarations
190 // (through 'eval'). The object in a 'with' statement is
191 // stored in the extension slot of a 'with' context.
192 // Dynamically declared variables/functions are also added
193 // to lazily allocated extension object. Context::Lookup
194 // searches the extension object for properties.
196 // [ global ] A pointer to the global object. Provided for quick
197 // access to the global object from inside the code (since
198 // we always have a context pointer).
200 // In addition, function contexts may have statically allocated context slots
201 // to store local variables/functions that are accessed from inner functions
202 // (via static context addresses) or through 'eval' (dynamic context lookups).
203 // Finally, the global context contains additional slots for fast access to
204 // global properties.
206 class Context: public FixedArray {
209 static Context* cast(Object* context) {
210 ASSERT(context->IsContext());
211 return reinterpret_cast<Context*>(context);
214 // The default context slot layout; indices are FixedArray slot indices.
216 // These slots are in all contexts.
219 // The extension slot is used for either the global object (in global
220 // contexts), eval extension object (function contexts), subject of with
221 // (with contexts), or the variable name (catch contexts), the serialized
222 // scope info (block contexts).
228 // This slot holds the thrown value in catch contexts.
229 THROWN_OBJECT_INDEX = MIN_CONTEXT_SLOTS,
231 // These slots are only in global contexts.
232 GLOBAL_PROXY_INDEX = MIN_CONTEXT_SLOTS,
233 SECURITY_TOKEN_INDEX,
234 ARGUMENTS_BOILERPLATE_INDEX,
235 ALIASED_ARGUMENTS_BOILERPLATE_INDEX,
236 STRICT_MODE_ARGUMENTS_BOILERPLATE_INDEX,
237 REGEXP_RESULT_MAP_INDEX,
239 STRICT_MODE_FUNCTION_MAP_INDEX,
240 FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX,
241 STRICT_MODE_FUNCTION_WITHOUT_PROTOTYPE_MAP_INDEX,
242 FUNCTION_INSTANCE_MAP_INDEX,
243 STRICT_MODE_FUNCTION_INSTANCE_MAP_INDEX,
244 INITIAL_OBJECT_PROTOTYPE_INDEX,
245 BOOLEAN_FUNCTION_INDEX,
246 NUMBER_FUNCTION_INDEX,
247 STRING_FUNCTION_INDEX,
248 STRING_FUNCTION_PROTOTYPE_MAP_INDEX,
249 OBJECT_FUNCTION_INDEX,
250 INTERNAL_ARRAY_FUNCTION_INDEX,
251 ARRAY_FUNCTION_INDEX,
252 SMI_JS_ARRAY_MAP_INDEX,
253 DOUBLE_JS_ARRAY_MAP_INDEX,
254 OBJECT_JS_ARRAY_MAP_INDEX,
257 REGEXP_FUNCTION_INDEX,
258 CREATE_DATE_FUN_INDEX,
261 TO_DETAIL_STRING_FUN_INDEX,
263 TO_INTEGER_FUN_INDEX,
266 TO_BOOLEAN_FUN_INDEX,
267 GLOBAL_EVAL_FUN_INDEX,
268 INSTANTIATE_FUN_INDEX,
269 CONFIGURE_INSTANCE_FUN_INDEX,
270 MESSAGE_LISTENERS_INDEX,
271 MAKE_MESSAGE_FUN_INDEX,
272 GET_STACK_TRACE_LINE_INDEX,
273 CONFIGURE_GLOBAL_INDEX,
274 FUNCTION_CACHE_INDEX,
275 JSFUNCTION_RESULT_CACHES_INDEX,
276 NORMALIZED_MAP_CACHE_INDEX,
277 RUNTIME_CONTEXT_INDEX,
278 CALL_AS_FUNCTION_DELEGATE_INDEX,
279 CALL_AS_CONSTRUCTOR_DELEGATE_INDEX,
280 SCRIPT_FUNCTION_INDEX,
281 OPAQUE_REFERENCE_FUNCTION_INDEX,
282 CONTEXT_EXTENSION_FUNCTION_INDEX,
285 ALLOW_CODE_GEN_FROM_STRINGS_INDEX,
286 TO_COMPLETE_PROPERTY_DESCRIPTOR_INDEX,
287 DERIVED_HAS_TRAP_INDEX,
288 DERIVED_GET_TRAP_INDEX,
289 DERIVED_SET_TRAP_INDEX,
293 // Properties from here are treated as weak references by the full GC.
294 // Scavenge treats them as strong references.
295 OPTIMIZED_FUNCTIONS_LIST, // Weak.
296 MAP_CACHE_INDEX, // Weak.
297 NEXT_CONTEXT_LINK, // Weak.
299 // Total number of slots.
300 GLOBAL_CONTEXT_SLOTS,
302 FIRST_WEAK_SLOT = OPTIMIZED_FUNCTIONS_LIST
305 // Direct slot access.
306 JSFunction* closure() { return JSFunction::cast(get(CLOSURE_INDEX)); }
307 void set_closure(JSFunction* closure) { set(CLOSURE_INDEX, closure); }
309 Context* previous() {
310 Object* result = unchecked_previous();
311 ASSERT(IsBootstrappingOrContext(result));
312 return reinterpret_cast<Context*>(result);
314 void set_previous(Context* context) { set(PREVIOUS_INDEX, context); }
316 bool has_extension() { return extension() != NULL; }
317 Object* extension() { return get(EXTENSION_INDEX); }
318 void set_extension(Object* object) { set(EXTENSION_INDEX, object); }
320 // Get the context where var declarations will be hoisted to, which
321 // may be the context itself.
322 Context* declaration_context();
324 GlobalObject* global() {
325 Object* result = get(GLOBAL_INDEX);
326 ASSERT(IsBootstrappingOrGlobalObject(result));
327 return reinterpret_cast<GlobalObject*>(result);
329 void set_global(GlobalObject* global) { set(GLOBAL_INDEX, global); }
331 JSObject *qml_global() { return reinterpret_cast<JSObject *>(get(QML_GLOBAL_INDEX)); }
332 void set_qml_global(JSObject *qml_global) { set(QML_GLOBAL_INDEX, qml_global); }
334 // Returns a JSGlobalProxy object or null.
335 JSObject* global_proxy();
336 void set_global_proxy(JSObject* global);
338 // The builtins object.
339 JSBuiltinsObject* builtins();
341 // Compute the global context by traversing the context chain.
342 Context* global_context();
344 // Predicates for context types. IsGlobalContext is defined on Object
345 // because we frequently have to know if arbitrary objects are global
347 bool IsFunctionContext() {
348 Map* map = this->map();
349 return map == map->GetHeap()->function_context_map();
351 bool IsCatchContext() {
352 Map* map = this->map();
353 return map == map->GetHeap()->catch_context_map();
355 bool IsWithContext() {
356 Map* map = this->map();
357 return map == map->GetHeap()->with_context_map();
359 bool IsBlockContext() {
360 Map* map = this->map();
361 return map == map->GetHeap()->block_context_map();
363 bool IsModuleContext() {
364 Map* map = this->map();
365 return map == map->GetHeap()->module_context_map();
368 // Tells whether the global context is marked with out of memory.
369 inline bool has_out_of_memory();
371 // Mark the global context with out of memory.
372 inline void mark_out_of_memory();
374 // A global context hold a list of all functions which have been optimized.
375 void AddOptimizedFunction(JSFunction* function);
376 void RemoveOptimizedFunction(JSFunction* function);
377 Object* OptimizedFunctionsListHead();
378 void ClearOptimizedFunctions();
380 static int GetContextMapIndexFromElementsKind(
381 ElementsKind elements_kind) {
382 if (elements_kind == FAST_DOUBLE_ELEMENTS) {
383 return Context::DOUBLE_JS_ARRAY_MAP_INDEX;
384 } else if (elements_kind == FAST_ELEMENTS) {
385 return Context::OBJECT_JS_ARRAY_MAP_INDEX;
387 ASSERT(elements_kind == FAST_SMI_ONLY_ELEMENTS);
388 return Context::SMI_JS_ARRAY_MAP_INDEX;
392 #define GLOBAL_CONTEXT_FIELD_ACCESSORS(index, type, name) \
393 void set_##name(type* value) { \
394 ASSERT(IsGlobalContext()); \
398 ASSERT(IsGlobalContext()); \
399 return type::cast(get(index)); \
401 GLOBAL_CONTEXT_FIELDS(GLOBAL_CONTEXT_FIELD_ACCESSORS)
402 #undef GLOBAL_CONTEXT_FIELD_ACCESSORS
404 // Lookup the slot called name, starting with the current context.
405 // There are three possibilities:
407 // 1) result->IsContext():
408 // The binding was found in a context. *index is always the
409 // non-negative slot index. *attributes is NONE for var and let
410 // declarations, READ_ONLY for const declarations (never ABSENT).
412 // 2) result->IsJSObject():
413 // The binding was found as a named property in a context extension
414 // object (i.e., was introduced via eval), as a property on the subject
415 // of with, or as a property of the global object. *index is -1 and
416 // *attributes is not ABSENT.
418 // 3) result.is_null():
419 // There was no binding found, *index is always -1 and *attributes is
421 Handle<Object> Lookup(Handle<String> name,
422 ContextLookupFlags flags,
424 PropertyAttributes* attributes,
425 BindingFlags* binding_flags);
427 // Code generation support.
428 static int SlotOffset(int index) {
429 return kHeaderSize + index * kPointerSize - kHeapObjectTag;
432 static const int kSize = kHeaderSize + GLOBAL_CONTEXT_SLOTS * kPointerSize;
435 typedef FixedBodyDescriptor<
436 kHeaderSize, kSize, kSize> ScavengeBodyDescriptor;
438 typedef FixedBodyDescriptor<
440 kHeaderSize + FIRST_WEAK_SLOT * kPointerSize,
441 kSize> MarkCompactBodyDescriptor;
444 // Unchecked access to the slots.
445 Object* unchecked_previous() { return get(PREVIOUS_INDEX); }
448 // Bootstrapping-aware type checks.
449 static bool IsBootstrappingOrContext(Object* object);
450 static bool IsBootstrappingOrGlobalObject(Object* object);
454 } } // namespace v8::internal
456 #endif // V8_CONTEXTS_H_