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src/runtime.cc

 // Copyright 2010 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 9944 matching lines @@
   // NOTE: This might require several heap iterations. If the SharedFunctionInfo
   // which is found is not compiled it is compiled and the heap is iterated
   // again as the compilation might create inner functions from the newly
   // compiled function and the actual requested break point might be in one of
   // these functions.
   bool done = false;
   // The current candidate for the source position:
   int target_start_position = RelocInfo::kNoPosition;
   Handle<SharedFunctionInfo> target;
   while (!done) {
-    HeapIterator iterator;
-    for (HeapObject* obj = iterator.Next();
-         obj != NULL; obj = iterator.Next()) {
-      if (obj->IsSharedFunctionInfo()) {
-        Handle<SharedFunctionInfo> shared(SharedFunctionInfo::cast(obj));
-        if (shared->script() == *script) {
-          // If the SharedFunctionInfo found has the requested script data and
-          // contains the source position it is a candidate.
-          int start_position = shared->function_token_position();
-          if (start_position == RelocInfo::kNoPosition) {
-            start_position = shared->start_position();
-          }
-          if (start_position <= position &&
-              position <= shared->end_position()) {
-            // If there is no candidate or this function is within the current
-            // candidate this is the new candidate.
-            if (target.is_null()) {
-              target_start_position = start_position;
-              target = shared;
-            } else {
-              if (target_start_position == start_position &&
-                  shared->end_position() == target->end_position()) {
-                  // If a top-level function contain only one function
-                  // declartion the source for the top-level and the function is
-                  // the same. In that case prefer the non top-level function.
-                if (!shared->is_toplevel()) {
+    { // Extra scope for iterator and no-allocation.
+      HeapIterator iterator;
+      AssertNoAllocation no_alloc_during_heap_iteration;
+      for (HeapObject* obj = iterator.Next();
+           obj != NULL; obj = iterator.Next()) {
+        if (obj->IsSharedFunctionInfo()) {
+          Handle<SharedFunctionInfo> shared(SharedFunctionInfo::cast(obj));
+          if (shared->script() == *script) {
+            // If the SharedFunctionInfo found has the requested script data and
+            // contains the source position it is a candidate.
+            int start_position = shared->function_token_position();
+            if (start_position == RelocInfo::kNoPosition) {
+              start_position = shared->start_position();
+            }
+            if (start_position <= position &&
+                position <= shared->end_position()) {
+              // If there is no candidate or this function is within the current
+              // candidate this is the new candidate.
+              if (target.is_null()) {
+                target_start_position = start_position;
+                target = shared;
+              } else {
+                if (target_start_position == start_position &&
+                    shared->end_position() == target->end_position()) {
+                    // If a top-level function contain only one function
+                    // declartion the source for the top-level and the
+                    // function is the same. In that case prefer the non
+                    // top-level function.
+                  if (!shared->is_toplevel()) {
+                    target_start_position = start_position;
+                    target = shared;
+                  }
+                } else if (target_start_position <= start_position &&
+                           shared->end_position() <= target->end_position()) {
+                  // This containment check includes equality as a function
+                  // inside a top-level function can share either start or end
+                  // position with the top-level function.
                   target_start_position = start_position;
                   target = shared;
                 }
-              } else if (target_start_position <= start_position &&
-                         shared->end_position() <= target->end_position()) {
-                // This containment check includes equality as a function inside
-                // a top-level function can share either start or end position
-                // with the top-level function.
-                target_start_position = start_position;
-                target = shared;
               }
             }
           }
         }
-      }
-    }
+      }  // End for loop.
+    }  // End No allocation scope.
 
     if (target.is_null()) {
       return Heap::undefined_value();
     }
 
     // If the candidate found is compiled we are done. NOTE: when lazy
     // compilation of inner functions is introduced some additional checking
     // needs to be done here to compile inner functions.
     done = target->is_compiled();
     if (!done) {
       // If the candidate is not compiled compile it to reveal any inner
       // functions which might contain the requested source position.
       CompileLazyShared(target, KEEP_EXCEPTION);
     }
-  }
+  }  // End while loop.
 
   return *target;
 }
 
 
 // Changes the state of a break point in a script and returns source position
 // where break point was set. NOTE: Regarding performance see the NOTE for
 // GetScriptFromScriptData.
 // args[0]: script to set break point in
 // args[1]: number: break source position (within the script source)
@@ skipping 409 matching lines @@
   }
 
   // Return result as a JS array.
   Handle<JSObject> result = Factory::NewJSObject(Top::array_function());
   Handle<JSArray>::cast(result)->SetContent(*instances);
   return *result;
 }
 
 
 // Helper function used by Runtime_DebugReferencedBy below.
-static int DebugReferencedBy(JSObject* target,
+static int DebugReferencedBy(HeapIterator* iterator,
+                             JSObject* target,
                              Object* instance_filter, int max_references,
                              FixedArray* instances, int instances_size,
                              JSFunction* arguments_function) {
   NoHandleAllocation ha;
-  HeapIterator iterator;
   AssertNoAllocation no_alloc;
 
   // Iterate the heap.
   int count = 0;
   JSObject* last = NULL;
   HeapObject* heap_obj = NULL;
-  while (((heap_obj = iterator.Next()) != NULL) &&
+  while (((heap_obj = iterator->Next()) != NULL) &&
          (max_references == 0 || count < max_references)) {
     // Only look at all JSObjects.
     if (heap_obj->IsJSObject()) {
       // Skip context extension objects and argument arrays as these are
       // checked in the context of functions using them.
       JSObject* obj = JSObject::cast(heap_obj);
       if (obj->IsJSContextExtensionObject() ||
           obj->map()->constructor() == arguments_function) {
         continue;
       }
@@ skipping 45 matching lines @@
 
 // Scan the heap for objects with direct references to an object
 // args[0]: the object to find references to
 // args[1]: constructor function for instances to exclude (Mirror)
 // args[2]: the the maximum number of objects to return
 static MaybeObject* Runtime_DebugReferencedBy(Arguments args) {
   ASSERT(args.length() == 3);
 
   // First perform a full GC in order to avoid references from dead objects.
   Heap::CollectAllGarbage(Heap::kMakeHeapIterableMask);
+  // The heap iterator reserves the right to do a GC to make the heap iterable.
+  // Due to the GC above we know it won't need to do that, but it seems cleaner
+  // to get the heap iterator constructed before we start having unprotected
+  // Object* locals that are not protected by handles.
+  HeapIterator heap_iterator;
+  HeapIterator heap_iterator2;
 
   // Check parameters.
   CONVERT_CHECKED(JSObject, target, args[0]);
   Object* instance_filter = args[1];
   RUNTIME_ASSERT(instance_filter->IsUndefined() ||
                  instance_filter->IsJSObject());
   CONVERT_NUMBER_CHECKED(int32_t, max_references, Int32, args[2]);
   RUNTIME_ASSERT(max_references >= 0);
 
+
   // Get the constructor function for context extension and arguments array.
   JSObject* arguments_boilerplate =
       Top::context()->global_context()->arguments_boilerplate();
   JSFunction* arguments_function =
       JSFunction::cast(arguments_boilerplate->map()->constructor());
 
   // Get the number of referencing objects.
   int count;
-  count = DebugReferencedBy(target, instance_filter, max_references,
+  count = DebugReferencedBy(&heap_iterator,
+                            target, instance_filter, max_references,
                             NULL, 0, arguments_function);
 
   // Allocate an array to hold the result.
   Object* object;
   { MaybeObject* maybe_object = Heap::AllocateFixedArray(count);
     if (!maybe_object->ToObject(&object)) return maybe_object;
   }
   FixedArray* instances = FixedArray::cast(object);
 
   // Fill the referencing objects.
-  count = DebugReferencedBy(target, instance_filter, max_references,
+  count = DebugReferencedBy(&heap_iterator2,
+                            target, instance_filter, max_references,
                             instances, count, arguments_function);
 
   // Return result as JS array.
   Object* result;
   { MaybeObject* maybe_result = Heap::AllocateJSObject(
         Top::context()->global_context()->array_function());
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   JSArray::cast(result)->SetContent(instances);
   return result;
 }
 
 
 // Helper function used by Runtime_DebugConstructedBy below.
-static int DebugConstructedBy(JSFunction* constructor, int max_references,
-                              FixedArray* instances, int instances_size) {
-  HeapIterator iterator;
+static int DebugConstructedBy(HeapIterator* iterator,
+                              JSFunction* constructor,
+                              int max_references,
+                              FixedArray* instances,
+                              int instances_size) {
   AssertNoAllocation no_alloc;
 
   // Iterate the heap.
   int count = 0;
   HeapObject* heap_obj = NULL;
-  while (((heap_obj = iterator.Next()) != NULL) &&
+  while (((heap_obj = iterator->Next()) != NULL) &&
          (max_references == 0 || count < max_references)) {
     // Only look at all JSObjects.
     if (heap_obj->IsJSObject()) {
       JSObject* obj = JSObject::cast(heap_obj);
       if (obj->map()->constructor() == constructor) {
         // Valid reference found add to instance array if supplied an update
         // count.
         if (instances != NULL && count < instances_size) {
           instances->set(count, obj);
         }
         count++;
       }
     }
   }
 
   // Return the number of referencing objects found.
   return count;
 }
 
 
 // Scan the heap for objects constructed by a specific function.
 // args[0]: the constructor to find instances of
 // args[1]: the the maximum number of objects to return
 static MaybeObject* Runtime_DebugConstructedBy(Arguments args) {
   ASSERT(args.length() == 2);
 
   // First perform a full GC in order to avoid dead objects.
   Heap::CollectAllGarbage(Heap::kMakeHeapIterableMask);
 
+  HeapIterator heap_iterator;
+  HeapIterator heap_iterator2;
+
   // Check parameters.
   CONVERT_CHECKED(JSFunction, constructor, args[0]);
   CONVERT_NUMBER_CHECKED(int32_t, max_references, Int32, args[1]);
   RUNTIME_ASSERT(max_references >= 0);
 
   // Get the number of referencing objects.
   int count;
-  count = DebugConstructedBy(constructor, max_references, NULL, 0);
+  count = DebugConstructedBy(&heap_iterator,
+                             constructor,
+                             max_references,
+                             NULL,
+                             0);
 
   // Allocate an array to hold the result.
   Object* object;
   { MaybeObject* maybe_object = Heap::AllocateFixedArray(count);
     if (!maybe_object->ToObject(&object)) return maybe_object;
   }
   FixedArray* instances = FixedArray::cast(object);
 
   // Fill the referencing objects.
-  count = DebugConstructedBy(constructor, max_references, instances, count);
+  count = DebugConstructedBy(&heap_iterator2,
+                             constructor,
+                             max_references,
+                             instances,
+                             count);
 
   // Return result as JS array.
   Object* result;
   { MaybeObject* maybe_result = Heap::AllocateJSObject(
         Top::context()->global_context()->array_function());
     if (!maybe_result->ToObject(&result)) return maybe_result;
   }
   JSArray::cast(result)->SetContent(instances);
   return result;
 }
@@ skipping 52 matching lines @@
 
 static MaybeObject* Runtime_FunctionGetInferredName(Arguments args) {
   NoHandleAllocation ha;
   ASSERT(args.length() == 1);
 
   CONVERT_CHECKED(JSFunction, f, args[0]);
   return f->shared()->inferred_name();
 }
 
 
-static int FindSharedFunctionInfosForScript(Script* script,
+static int FindSharedFunctionInfosForScript(HeapIterator* iterator,
+                                            Script* script,
                                             FixedArray* buffer) {
-  HeapIterator iterator;
-  AssertNoAllocation no_allocations;
-
   int counter = 0;
   int buffer_size = buffer->length();
-  for (HeapObject* obj = iterator.Next(); obj != NULL; obj = iterator.Next()) {
+  for (HeapObject* obj = iterator->Next();
+       obj != NULL;
+       obj = iterator->Next()) {
     ASSERT(obj != NULL);
     if (!obj->IsSharedFunctionInfo()) {
       continue;
     }
     SharedFunctionInfo* shared = SharedFunctionInfo::cast(obj);
     if (shared->script() != script) {
       continue;
     }
     if (counter < buffer_size) {
       buffer->set(counter, shared);
@@ skipping 12 matching lines @@
   HandleScope scope;
   CONVERT_CHECKED(JSValue, script_value, args[0]);
 
 
   Handle<Script> script = Handle<Script>(Script::cast(script_value->value()));
 
   const int kBufferSize = 32;
 
   Handle<FixedArray> array;
   array = Factory::NewFixedArray(kBufferSize);
-  int number = FindSharedFunctionInfosForScript(*script, *array);
+  int number;
+  {
+    HeapIterator heap_iterator;
+    AssertNoAllocation no_allocations;
+    Script* scr = *script;
+    FixedArray* arr = *array;
+    number = FindSharedFunctionInfosForScript(&heap_iterator, scr, arr);
+  }
   if (number > kBufferSize) {
     array = Factory::NewFixedArray(number);
-    FindSharedFunctionInfosForScript(*script, *array);
+    HeapIterator heap_iterator;
+    AssertNoAllocation no_allocations;
+    Script* scr = *script;
+    FixedArray* arr = *array;
+    FindSharedFunctionInfosForScript(&heap_iterator, scr, arr);
   }
 
   Handle<JSArray> result = Factory::NewJSArrayWithElements(array);
   result->set_length(Smi::FromInt(number));
 
   LiveEdit::WrapSharedFunctionInfos(result);
 
   return *result;
 }
 
@@ skipping 472 matching lines @@
 // for the requested break point. For lazily compiled functions several heap
 // traversals might be required rendering this operation as a rather slow
 // operation. However for setting break points which is normally done through
 // some kind of user interaction the performance is not crucial.
 static Handle<Object> Runtime_GetScriptFromScriptName(
     Handle<String> script_name) {
   // Scan the heap for Script objects to find the script with the requested
   // script data.
   Handle<Script> script;
   HeapIterator iterator;
+  AssertNoAllocation no_allocation_during_heap_iteration;
   HeapObject* obj = NULL;
   while (script.is_null() && ((obj = iterator.Next()) != NULL)) {
     // If a script is found check if it has the script data requested.
     if (obj->IsScript()) {
       if (Script::cast(obj)->name()->IsString()) {
         if (String::cast(Script::cast(obj)->name())->Equals(*script_name)) {
           script = Handle<Script>(Script::cast(obj));
         }
       }
     }
@@ skipping 394 matching lines @@
   } else {
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     Counters::gc_last_resort_from_js.Increment();
     Heap::CollectAllGarbage(Heap::kNoGCFlags);
   }
 }
 
 
 } }  // namespace v8::internal