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1 // Copyright 2012 the V8 project authors. All rights reserved. | 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 | 2 // Use of this source code is governed by a BSD-style license that can be |
3 // found in the LICENSE file. | 3 // found in the LICENSE file. |
4 | 4 |
5 #ifndef V8_CONTEXTS_H_ | 5 #ifndef V8_CONTEXTS_H_ |
6 #define V8_CONTEXTS_H_ | 6 #define V8_CONTEXTS_H_ |
7 | 7 |
8 #include "src/heap/heap.h" | 8 #include "src/heap/heap.h" |
9 #include "src/objects.h" | 9 #include "src/objects.h" |
10 | 10 |
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23 LEXICAL_TEST = | 23 LEXICAL_TEST = |
24 FOLLOW_CONTEXT_CHAIN | STOP_AT_DECLARATION_SCOPE | SKIP_WITH_CONTEXT, | 24 FOLLOW_CONTEXT_CHAIN | STOP_AT_DECLARATION_SCOPE | SKIP_WITH_CONTEXT, |
25 }; | 25 }; |
26 | 26 |
27 | 27 |
28 // ES5 10.2 defines lexical environments with mutable and immutable bindings. | 28 // ES5 10.2 defines lexical environments with mutable and immutable bindings. |
29 // Immutable bindings have two states, initialized and uninitialized, and | 29 // Immutable bindings have two states, initialized and uninitialized, and |
30 // their state is changed by the InitializeImmutableBinding method. The | 30 // their state is changed by the InitializeImmutableBinding method. The |
31 // BindingFlags enum represents information if a binding has definitely been | 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 | 32 // initialized. A mutable binding does not need to be checked and thus has |
33 // the BindingFlag MUTABLE_IS_INITIALIZED. | 33 // the BindingFlag BINDING_IS_INITIALIZED. |
34 // | 34 // |
35 // There are two possibilities for immutable bindings | 35 // There is one possibility for legacy 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 | 36 // * 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 | 37 // initialized when entering the function and thus does not need to be |
41 // checked. it gets the BindingFlag IMMUTABLE_IS_INITIALIZED. | 38 // checked. it gets the BindingFlag BINDING_IS_INITIALIZED. |
42 // Accessing an uninitialized binding produces the undefined value. | |
43 // | 39 // |
44 // The harmony proposal for block scoped bindings also introduces the | 40 // The harmony proposal for block scoped bindings also introduces the |
45 // uninitialized state for mutable bindings. | 41 // uninitialized state for mutable bindings. |
46 // * A 'let' declared variable. They are initialized when evaluating the | 42 // * A 'let' declared variable. They are initialized when evaluating the |
47 // corresponding declaration statement. They need to be checked for being | 43 // corresponding declaration statement. They need to be checked for being |
48 // initialized and thus get the flag MUTABLE_CHECK_INITIALIZED. | 44 // initialized and thus get the flag BINDING_CHECK_INITIALIZED. |
49 // * A 'var' declared variable. It is initialized immediately upon creation | 45 // * A 'var' declared variable. It is initialized immediately upon creation |
50 // and thus doesn't need to be checked. It gets the flag | 46 // and thus doesn't need to be checked. It gets the flag |
51 // MUTABLE_IS_INITIALIZED. | 47 // BINDING_IS_INITIALIZED. |
52 // * Catch bound variables, function parameters and variables introduced by | 48 // * Catch bound variables, function parameters and variables introduced by |
53 // function declarations are initialized immediately and do not need to be | 49 // function declarations are initialized immediately and do not need to be |
54 // checked. Thus they get the flag MUTABLE_IS_INITIALIZED. | 50 // checked. Thus they get the flag BINDING_IS_INITIALIZED. |
55 // Immutable bindings in harmony mode get the _HARMONY flag variants. Accessing | 51 // Accessing an uninitialized binding produces a reference error. |
56 // an uninitialized binding produces a reference error. | |
57 // | 52 // |
58 // In V8 uninitialized bindings are set to the hole value upon creation and set | 53 // In V8 uninitialized bindings are set to the hole value upon creation and set |
59 // to a different value upon initialization. | 54 // to a different value upon initialization. |
60 enum BindingFlags { | 55 enum BindingFlags { |
61 MUTABLE_IS_INITIALIZED, | 56 BINDING_IS_INITIALIZED, |
62 MUTABLE_CHECK_INITIALIZED, | 57 BINDING_CHECK_INITIALIZED, |
63 IMMUTABLE_IS_INITIALIZED, | |
64 IMMUTABLE_CHECK_INITIALIZED, | |
65 IMMUTABLE_IS_INITIALIZED_HARMONY, | |
66 IMMUTABLE_CHECK_INITIALIZED_HARMONY, | |
67 MISSING_BINDING | 58 MISSING_BINDING |
68 }; | 59 }; |
69 | 60 |
70 | |
71 // Heap-allocated activation contexts. | 61 // Heap-allocated activation contexts. |
72 // | 62 // |
73 // Contexts are implemented as FixedArray objects; the Context | 63 // Contexts are implemented as FixedArray objects; the Context |
74 // class is a convenience interface casted on a FixedArray object. | 64 // class is a convenience interface casted on a FixedArray object. |
75 // | 65 // |
76 // Note: Context must have no virtual functions and Context objects | 66 // Note: Context must have no virtual functions and Context objects |
77 // must always be allocated via Heap::AllocateContext() or | 67 // must always be allocated via Heap::AllocateContext() or |
78 // Factory::NewContext. | 68 // Factory::NewContext. |
79 | 69 |
80 #define NATIVE_CONTEXT_INTRINSIC_FUNCTIONS(V) \ | 70 #define NATIVE_CONTEXT_INTRINSIC_FUNCTIONS(V) \ |
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570 #endif | 560 #endif |
571 | 561 |
572 STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize); | 562 STATIC_ASSERT(kHeaderSize == Internals::kContextHeaderSize); |
573 STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex); | 563 STATIC_ASSERT(EMBEDDER_DATA_INDEX == Internals::kContextEmbedderDataIndex); |
574 }; | 564 }; |
575 | 565 |
576 } // namespace internal | 566 } // namespace internal |
577 } // namespace v8 | 567 } // namespace v8 |
578 | 568 |
579 #endif // V8_CONTEXTS_H_ | 569 #endif // V8_CONTEXTS_H_ |
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