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      1 // Copyright 2011 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
      4 // met:
      5 //
      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.
     15 //
     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.
     27 
     28 #include "v8.h"
     29 
     30 #include "bootstrapper.h"
     31 #include "debug.h"
     32 #include "scopeinfo.h"
     33 
     34 namespace v8 {
     35 namespace internal {
     36 
     37 Context* Context::declaration_context() {
     38   Context* current = this;
     39   while (!current->IsFunctionContext() && !current->IsNativeContext()) {
     40     current = current->previous();
     41     ASSERT(current->closure() == closure());
     42   }
     43   return current;
     44 }
     45 
     46 
     47 JSBuiltinsObject* Context::builtins() {
     48   GlobalObject* object = global_object();
     49   if (object->IsJSGlobalObject()) {
     50     return JSGlobalObject::cast(object)->builtins();
     51   } else {
     52     ASSERT(object->IsJSBuiltinsObject());
     53     return JSBuiltinsObject::cast(object);
     54   }
     55 }
     56 
     57 
     58 Context* Context::global_context() {
     59   Context* current = this;
     60   while (!current->IsGlobalContext()) {
     61     current = current->previous();
     62   }
     63   return current;
     64 }
     65 
     66 
     67 Context* Context::native_context() {
     68   // Fast case: the global object for this context has been set.  In
     69   // that case, the global object has a direct pointer to the global
     70   // context.
     71   if (global_object()->IsGlobalObject()) {
     72     return global_object()->native_context();
     73   }
     74 
     75   // During bootstrapping, the global object might not be set and we
     76   // have to search the context chain to find the native context.
     77   ASSERT(Isolate::Current()->bootstrapper()->IsActive());
     78   Context* current = this;
     79   while (!current->IsNativeContext()) {
     80     JSFunction* closure = JSFunction::cast(current->closure());
     81     current = Context::cast(closure->context());
     82   }
     83   return current;
     84 }
     85 
     86 
     87 JSObject* Context::global_proxy() {
     88   return native_context()->global_proxy_object();
     89 }
     90 
     91 
     92 void Context::set_global_proxy(JSObject* object) {
     93   native_context()->set_global_proxy_object(object);
     94 }
     95 
     96 
     97 Handle<Object> Context::Lookup(Handle<String> name,
     98                                ContextLookupFlags flags,
     99                                int* index,
    100                                PropertyAttributes* attributes,
    101                                BindingFlags* binding_flags) {
    102   Isolate* isolate = GetIsolate();
    103   Handle<Context> context(this, isolate);
    104 
    105   bool follow_context_chain = (flags & FOLLOW_CONTEXT_CHAIN) != 0;
    106   *index = -1;
    107   *attributes = ABSENT;
    108   *binding_flags = MISSING_BINDING;
    109 
    110   if (FLAG_trace_contexts) {
    111     PrintF("Context::Lookup(");
    112     name->ShortPrint();
    113     PrintF(")\n");
    114   }
    115 
    116   do {
    117     if (FLAG_trace_contexts) {
    118       PrintF(" - looking in context %p", reinterpret_cast<void*>(*context));
    119       if (context->IsNativeContext()) PrintF(" (native context)");
    120       PrintF("\n");
    121     }
    122 
    123     // 1. Check global objects, subjects of with, and extension objects.
    124     if (context->IsNativeContext() ||
    125         context->IsWithContext() ||
    126         (context->IsFunctionContext() && context->has_extension())) {
    127       Handle<JSReceiver> object(
    128           JSReceiver::cast(context->extension()), isolate);
    129       // Context extension objects needs to behave as if they have no
    130       // prototype.  So even if we want to follow prototype chains, we need
    131       // to only do a local lookup for context extension objects.
    132       if ((flags & FOLLOW_PROTOTYPE_CHAIN) == 0 ||
    133           object->IsJSContextExtensionObject()) {
    134         *attributes = object->GetLocalPropertyAttribute(*name);
    135       } else {
    136         *attributes = object->GetPropertyAttribute(*name);
    137       }
    138       if (isolate->has_pending_exception()) return Handle<Object>();
    139 
    140       if (*attributes != ABSENT) {
    141         if (FLAG_trace_contexts) {
    142           PrintF("=> found property in context object %p\n",
    143                  reinterpret_cast<void*>(*object));
    144         }
    145         return object;
    146       }
    147     }
    148 
    149     // 2. Check the context proper if it has slots.
    150     if (context->IsFunctionContext() || context->IsBlockContext()) {
    151       // Use serialized scope information of functions and blocks to search
    152       // for the context index.
    153       Handle<ScopeInfo> scope_info;
    154       if (context->IsFunctionContext()) {
    155         scope_info = Handle<ScopeInfo>(
    156             context->closure()->shared()->scope_info(), isolate);
    157       } else {
    158         scope_info = Handle<ScopeInfo>(
    159             ScopeInfo::cast(context->extension()), isolate);
    160       }
    161       VariableMode mode;
    162       InitializationFlag init_flag;
    163       int slot_index = scope_info->ContextSlotIndex(*name, &mode, &init_flag);
    164       ASSERT(slot_index < 0 || slot_index >= MIN_CONTEXT_SLOTS);
    165       if (slot_index >= 0) {
    166         if (FLAG_trace_contexts) {
    167           PrintF("=> found local in context slot %d (mode = %d)\n",
    168                  slot_index, mode);
    169         }
    170         *index = slot_index;
    171         // Note: Fixed context slots are statically allocated by the compiler.
    172         // Statically allocated variables always have a statically known mode,
    173         // which is the mode with which they were declared when added to the
    174         // scope. Thus, the DYNAMIC mode (which corresponds to dynamically
    175         // declared variables that were introduced through declaration nodes)
    176         // must not appear here.
    177         switch (mode) {
    178           case INTERNAL:  // Fall through.
    179           case VAR:
    180             *attributes = NONE;
    181             *binding_flags = MUTABLE_IS_INITIALIZED;
    182             break;
    183           case LET:
    184             *attributes = NONE;
    185             *binding_flags = (init_flag == kNeedsInitialization)
    186                 ? MUTABLE_CHECK_INITIALIZED : MUTABLE_IS_INITIALIZED;
    187             break;
    188           case CONST:
    189             *attributes = READ_ONLY;
    190             *binding_flags = (init_flag == kNeedsInitialization)
    191                 ? IMMUTABLE_CHECK_INITIALIZED : IMMUTABLE_IS_INITIALIZED;
    192             break;
    193           case CONST_HARMONY:
    194             *attributes = READ_ONLY;
    195             *binding_flags = (init_flag == kNeedsInitialization)
    196                 ? IMMUTABLE_CHECK_INITIALIZED_HARMONY :
    197                 IMMUTABLE_IS_INITIALIZED_HARMONY;
    198             break;
    199           case MODULE:
    200             *attributes = READ_ONLY;
    201             *binding_flags = IMMUTABLE_IS_INITIALIZED_HARMONY;
    202             break;
    203           case DYNAMIC:
    204           case DYNAMIC_GLOBAL:
    205           case DYNAMIC_LOCAL:
    206           case TEMPORARY:
    207             UNREACHABLE();
    208             break;
    209         }
    210         return context;
    211       }
    212 
    213       // Check the slot corresponding to the intermediate context holding
    214       // only the function name variable.
    215       if (follow_context_chain && context->IsFunctionContext()) {
    216         VariableMode mode;
    217         int function_index = scope_info->FunctionContextSlotIndex(*name, &mode);
    218         if (function_index >= 0) {
    219           if (FLAG_trace_contexts) {
    220             PrintF("=> found intermediate function in context slot %d\n",
    221                    function_index);
    222           }
    223           *index = function_index;
    224           *attributes = READ_ONLY;
    225           ASSERT(mode == CONST || mode == CONST_HARMONY);
    226           *binding_flags = (mode == CONST)
    227               ? IMMUTABLE_IS_INITIALIZED : IMMUTABLE_IS_INITIALIZED_HARMONY;
    228           return context;
    229         }
    230       }
    231 
    232     } else if (context->IsCatchContext()) {
    233       // Catch contexts have the variable name in the extension slot.
    234       if (name->Equals(String::cast(context->extension()))) {
    235         if (FLAG_trace_contexts) {
    236           PrintF("=> found in catch context\n");
    237         }
    238         *index = Context::THROWN_OBJECT_INDEX;
    239         *attributes = NONE;
    240         *binding_flags = MUTABLE_IS_INITIALIZED;
    241         return context;
    242       }
    243     }
    244 
    245     // 3. Prepare to continue with the previous (next outermost) context.
    246     if (context->IsNativeContext()) {
    247       follow_context_chain = false;
    248     } else {
    249       context = Handle<Context>(context->previous(), isolate);
    250     }
    251   } while (follow_context_chain);
    252 
    253   if (FLAG_trace_contexts) {
    254     PrintF("=> no property/slot found\n");
    255   }
    256   return Handle<Object>::null();
    257 }
    258 
    259 
    260 void Context::AddOptimizedFunction(JSFunction* function) {
    261   ASSERT(IsNativeContext());
    262 #ifdef DEBUG
    263   if (FLAG_enable_slow_asserts) {
    264     Object* element = get(OPTIMIZED_FUNCTIONS_LIST);
    265     while (!element->IsUndefined()) {
    266       CHECK(element != function);
    267       element = JSFunction::cast(element)->next_function_link();
    268     }
    269   }
    270 
    271   // Check that the context belongs to the weak native contexts list.
    272   bool found = false;
    273   Object* context = GetHeap()->native_contexts_list();
    274   while (!context->IsUndefined()) {
    275     if (context == this) {
    276       found = true;
    277       break;
    278     }
    279     context = Context::cast(context)->get(Context::NEXT_CONTEXT_LINK);
    280   }
    281   CHECK(found);
    282 #endif
    283 
    284   // If the function link field is already used then the function was
    285   // enqueued as a code flushing candidate and we remove it now.
    286   if (!function->next_function_link()->IsUndefined()) {
    287     CodeFlusher* flusher = GetHeap()->mark_compact_collector()->code_flusher();
    288     flusher->EvictCandidate(function);
    289   }
    290 
    291   ASSERT(function->next_function_link()->IsUndefined());
    292 
    293   function->set_next_function_link(get(OPTIMIZED_FUNCTIONS_LIST));
    294   set(OPTIMIZED_FUNCTIONS_LIST, function);
    295 }
    296 
    297 
    298 void Context::RemoveOptimizedFunction(JSFunction* function) {
    299   ASSERT(IsNativeContext());
    300   Object* element = get(OPTIMIZED_FUNCTIONS_LIST);
    301   JSFunction* prev = NULL;
    302   while (!element->IsUndefined()) {
    303     JSFunction* element_function = JSFunction::cast(element);
    304     ASSERT(element_function->next_function_link()->IsUndefined() ||
    305            element_function->next_function_link()->IsJSFunction());
    306     if (element_function == function) {
    307       if (prev == NULL) {
    308         set(OPTIMIZED_FUNCTIONS_LIST, element_function->next_function_link());
    309       } else {
    310         prev->set_next_function_link(element_function->next_function_link());
    311       }
    312       element_function->set_next_function_link(GetHeap()->undefined_value());
    313       return;
    314     }
    315     prev = element_function;
    316     element = element_function->next_function_link();
    317   }
    318   UNREACHABLE();
    319 }
    320 
    321 
    322 Object* Context::OptimizedFunctionsListHead() {
    323   ASSERT(IsNativeContext());
    324   return get(OPTIMIZED_FUNCTIONS_LIST);
    325 }
    326 
    327 
    328 void Context::ClearOptimizedFunctions() {
    329   set(OPTIMIZED_FUNCTIONS_LIST, GetHeap()->undefined_value());
    330 }
    331 
    332 
    333 Handle<Object> Context::ErrorMessageForCodeGenerationFromStrings() {
    334   Handle<Object> result(error_message_for_code_gen_from_strings(),
    335                         GetIsolate());
    336   if (!result->IsUndefined()) return result;
    337   return GetIsolate()->factory()->NewStringFromAscii(i::CStrVector(
    338       "Code generation from strings disallowed for this context"));
    339 }
    340 
    341 
    342 #ifdef DEBUG
    343 bool Context::IsBootstrappingOrValidParentContext(
    344     Object* object, Context* child) {
    345   // During bootstrapping we allow all objects to pass as
    346   // contexts. This is necessary to fix circular dependencies.
    347   if (child->GetIsolate()->bootstrapper()->IsActive()) return true;
    348   if (!object->IsContext()) return false;
    349   Context* context = Context::cast(object);
    350   return context->IsNativeContext() || context->IsGlobalContext() ||
    351          context->IsModuleContext() || !child->IsModuleContext();
    352 }
    353 
    354 
    355 bool Context::IsBootstrappingOrGlobalObject(Object* object) {
    356   // During bootstrapping we allow all objects to pass as global
    357   // objects. This is necessary to fix circular dependencies.
    358   Isolate* isolate = Isolate::Current();
    359   return isolate->heap()->gc_state() != Heap::NOT_IN_GC ||
    360       isolate->bootstrapper()->IsActive() ||
    361       object->IsGlobalObject();
    362 }
    363 #endif
    364 
    365 } }  // namespace v8::internal
    366