Debugger: refactor ScopeIterator, FrameInspector and DebugEvaluate.

src/debug/debug-evaluate.cc

+// Copyright 2015 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "src/debug/debug-evaluate.h"
+
+#include "src/accessors.h"
+#include "src/contexts.h"
+#include "src/debug/debug.h"
+#include "src/debug/debug-frames.h"
+#include "src/debug/debug-scopes.h"
+#include "src/isolate.h"
+
+namespace v8 {
+namespace internal {
+
+
+static inline bool IsDebugContext(Isolate* isolate, Context* context) {
+  // Try to unwrap script context if it exist.
+  if (context->IsScriptContext()) context = context->previous();
+  DCHECK_NOT_NULL(context);
+  return context == *isolate->debug()->debug_context();
+}
+
+
+MaybeHandle<Object> DebugEvaluate::Global(Isolate* isolate,
+                                          Handle<String> source,
+                                          bool disable_break,
+                                          Handle<Object> context_extension) {
+  // Handle the processing of break.
+  DisableBreak disable_break_scope(isolate->debug(), disable_break);
+
+  // Enter the top context from before the debugger was invoked.
+  SaveContext save(isolate);
+  SaveContext* top = &save;
+  while (top != NULL && IsDebugContext(isolate, *top->context())) {
+    top = top->prev();
+  }
+  if (top != NULL) isolate->set_context(*top->context());
+
+  // Get the native context now set to the top context from before the
+  // debugger was invoked.
+  Handle<Context> context = isolate->native_context();
+  Handle<JSObject> receiver(context->global_proxy());
+  Handle<SharedFunctionInfo> outer_info(context->closure()->shared(), isolate);
+  return Evaluate(isolate, outer_info, context, context_extension, receiver,
+                  source);
+}
+
+
+MaybeHandle<Object> DebugEvaluate::Local(Isolate* isolate,
+                                         StackFrame::Id frame_id,
+                                         int inlined_jsframe_index,
+                                         Handle<String> source,
+                                         bool disable_break,
+                                         Handle<Object> context_extension) {
+  // Handle the processing of break.
+  DisableBreak disable_break_scope(isolate->debug(), disable_break);
+
+  // Get the frame where the debugging is performed.
+  JavaScriptFrameIterator it(isolate, frame_id);
+  JavaScriptFrame* frame = it.frame();
+
+  // Traverse the saved contexts chain to find the active context for the
+  // selected frame.
+  SaveContext* save =
+      DebugFrameHelper::FindSavedContextForFrame(isolate, frame);
+  SaveContext savex(isolate);
+  isolate->set_context(*(save->context()));
+
+  // Materialize stack locals and the arguments object.
+  ContextBuilder context_builder(isolate, frame, inlined_jsframe_index);
+  if (isolate->has_pending_exception()) return MaybeHandle<Object>();
+
+  Handle<Object> receiver(frame->receiver(), isolate);
+  MaybeHandle<Object> maybe_result = Evaluate(
+      isolate, context_builder.outer_info(),
+      context_builder.innermost_context(), context_extension, receiver, source);
+  if (!maybe_result.is_null()) context_builder.UpdateValues();
+  return maybe_result;
+}
+
+
+// Compile and evaluate source for the given context.
+MaybeHandle<Object> DebugEvaluate::Evaluate(
+    Isolate* isolate, Handle<SharedFunctionInfo> outer_info,
+    Handle<Context> context, Handle<Object> context_extension,
+    Handle<Object> receiver, Handle<String> source) {
+  if (context_extension->IsJSObject()) {
+    Handle<JSObject> extension = Handle<JSObject>::cast(context_extension);
+    Handle<JSFunction> closure(context->closure(), isolate);
+    context = isolate->factory()->NewWithContext(closure, context, extension);
+  }
+
+  Handle<JSFunction> eval_fun;
+  ASSIGN_RETURN_ON_EXCEPTION(isolate, eval_fun,
+                             Compiler::GetFunctionFromEval(
+                                 source, outer_info, context, SLOPPY,
+                                 NO_PARSE_RESTRICTION, RelocInfo::kNoPosition),
+                             Object);
+
+  Handle<Object> result;
+  ASSIGN_RETURN_ON_EXCEPTION(
+      isolate, result, Execution::Call(isolate, eval_fun, receiver, 0, NULL),
+      Object);
+
+  // Skip the global proxy as it has no properties and always delegates to the
+  // real global object.
+  if (result->IsJSGlobalProxy()) {
+    PrototypeIterator iter(isolate, result);
+    // TODO(verwaest): This will crash when the global proxy is detached.
+    result = Handle<JSObject>::cast(PrototypeIterator::GetCurrent(iter));
+  }
+
+  return result;
+}
+
+
+DebugEvaluate::ContextBuilder::ContextBuilder(Isolate* isolate,
+                                              JavaScriptFrame* frame,
+                                              int inlined_jsframe_index)
+    : isolate_(isolate),
+      frame_(frame),
+      inlined_jsframe_index_(inlined_jsframe_index) {
+  FrameInspector frame_inspector(frame, inlined_jsframe_index, isolate);
+  Handle<JSFunction> function =
+      handle(JSFunction::cast(frame_inspector.GetFunction()));
+  Handle<Context> outer_context = handle(function->context(), isolate);
+  outer_info_ = handle(function->shared());
+  Handle<Context> inner_context;
+
+  bool stop = false;
+  for (ScopeIterator it(isolate, &frame_inspector);
+       !it.Failed() && !it.Done() && !stop; it.Next()) {
+    ScopeIterator::ScopeType scope_type = it.Type();
+
+    if (scope_type == ScopeIterator::ScopeTypeLocal) {
+      Handle<Context> parent_context =
+          it.HasContext() ? it.CurrentContext() : outer_context;
+
+      // The "this" binding, if any, can't be bound via "with".  If we need
+      // to, add another node onto the outer context to bind "this".
+      parent_context = MaterializeReceiver(parent_context, function);
+
+      Handle<JSObject> materialized_function = NewJSObjectWithNullProto();
+
+      frame_inspector.MaterializeStackLocals(materialized_function, function);
+
+      MaterializeArgumentsObject(materialized_function, function);
+
+      Handle<Context> with_context = isolate->factory()->NewWithContext(
+          function, parent_context, materialized_function);
+
+      ContextChainElement context_chain_element;
+      context_chain_element.original_context = it.CurrentContext();
+      context_chain_element.materialized_object = materialized_function;
+      context_chain_element.scope_info = it.CurrentScopeInfo();
+      context_chain_.Add(context_chain_element);
+
+      stop = true;
+      RecordContextsInChain(&inner_context, with_context, with_context);
+    } else if (scope_type == ScopeIterator::ScopeTypeCatch ||
+               scope_type == ScopeIterator::ScopeTypeWith) {
+      Handle<Context> cloned_context =
+          Handle<Context>::cast(FixedArray::CopySize(
+              it.CurrentContext(), it.CurrentContext()->length()));
+
+      ContextChainElement context_chain_element;
+      context_chain_element.original_context = it.CurrentContext();
+      context_chain_element.cloned_context = cloned_context;
+      context_chain_.Add(context_chain_element);
+
+      RecordContextsInChain(&inner_context, cloned_context, cloned_context);
+    } else if (scope_type == ScopeIterator::ScopeTypeBlock) {
+      Handle<JSObject> materialized_object = NewJSObjectWithNullProto();
+      frame_inspector.MaterializeStackLocals(materialized_object,
+                                             it.CurrentScopeInfo());
+      if (it.HasContext()) {
+        Handle<Context> cloned_context =
+            Handle<Context>::cast(FixedArray::CopySize(
+                it.CurrentContext(), it.CurrentContext()->length()));
+        Handle<Context> with_context = isolate->factory()->NewWithContext(
+            function, cloned_context, materialized_object);
+
+        ContextChainElement context_chain_element;
+        context_chain_element.original_context = it.CurrentContext();
+        context_chain_element.cloned_context = cloned_context;
+        context_chain_element.materialized_object = materialized_object;
+        context_chain_element.scope_info = it.CurrentScopeInfo();
+        context_chain_.Add(context_chain_element);
+
+        RecordContextsInChain(&inner_context, cloned_context, with_context);
+      } else {
+        Handle<Context> with_context = isolate->factory()->NewWithContext(
+            function, outer_context, materialized_object);
+
+        ContextChainElement context_chain_element;
+        context_chain_element.materialized_object = materialized_object;
+        context_chain_element.scope_info = it.CurrentScopeInfo();
+        context_chain_.Add(context_chain_element);
+
+        RecordContextsInChain(&inner_context, with_context, with_context);
+      }
+    } else {
+      stop = true;
+    }
+  }
+  if (innermost_context_.is_null()) {
+    innermost_context_ = outer_context;
+  }
+  DCHECK(!innermost_context_.is_null());
+}
+
+
+void DebugEvaluate::ContextBuilder::UpdateValues() {
+  for (int i = 0; i < context_chain_.length(); i++) {
+    ContextChainElement element = context_chain_[i];
+    if (!element.original_context.is_null() &&
+        !element.cloned_context.is_null()) {
+      Handle<Context> cloned_context = element.cloned_context;
+      cloned_context->CopyTo(
+          Context::MIN_CONTEXT_SLOTS, *element.original_context,
+          Context::MIN_CONTEXT_SLOTS,
+          cloned_context->length() - Context::MIN_CONTEXT_SLOTS);
+    }
+    if (!element.materialized_object.is_null()) {
+      // Write back potential changes to materialized stack locals to the
+      // stack.
+      FrameInspector(frame_, inlined_jsframe_index_, isolate_)
+          .UpdateStackLocalsFromMaterializedObject(element.materialized_object,
+                                                   element.scope_info);
+    }
+  }
+}
+
+
+Handle<JSObject> DebugEvaluate::ContextBuilder::NewJSObjectWithNullProto() {
+  Handle<JSObject> result =
+      isolate_->factory()->NewJSObject(isolate_->object_function());
+  Handle<Map> new_map =
+      Map::Copy(Handle<Map>(result->map()), "ObjectWithNullProto");
+  Map::SetPrototype(new_map, isolate_->factory()->null_value());
+  JSObject::MigrateToMap(result, new_map);
+  return result;
+}
+
+
+void DebugEvaluate::ContextBuilder::RecordContextsInChain(
+    Handle<Context>* inner_context, Handle<Context> first,
+    Handle<Context> last) {
+  if (!inner_context->is_null()) {
+    (*inner_context)->set_previous(*last);
+  } else {
+    innermost_context_ = last;
+  }
+  *inner_context = first;
+}
+
+
+void DebugEvaluate::ContextBuilder::MaterializeArgumentsObject(
+    Handle<JSObject> target, Handle<JSFunction> function) {
+  // Do not materialize the arguments object for eval or top-level code.
+  // Skip if "arguments" is already taken.
+  if (!function->shared()->is_function()) return;
+  Maybe<bool> maybe = JSReceiver::HasOwnProperty(
+      target, isolate_->factory()->arguments_string());
+  DCHECK(maybe.IsJust());
+  if (maybe.FromJust()) return;
+
+  // FunctionGetArguments can't throw an exception.
+  Handle<JSObject> arguments =
+      Handle<JSObject>::cast(Accessors::FunctionGetArguments(function));
+  Handle<String> arguments_str = isolate_->factory()->arguments_string();
+  JSObject::SetOwnPropertyIgnoreAttributes(target, arguments_str, arguments,
+                                           NONE)
+      .Check();
+}
+
+
+Handle<Context> DebugEvaluate::ContextBuilder::MaterializeReceiver(
+    Handle<Context> target, Handle<JSFunction> function) {
+  Handle<SharedFunctionInfo> shared(function->shared());
+  Handle<ScopeInfo> scope_info(shared->scope_info());
+  Handle<Object> receiver;
+  switch (scope_info->scope_type()) {
+    case FUNCTION_SCOPE: {
+      VariableMode mode;
+      VariableLocation location;
+      InitializationFlag init_flag;
+      MaybeAssignedFlag maybe_assigned_flag;
+
+      // Don't bother creating a fake context node if "this" is in the context
+      // already.
+      if (ScopeInfo::ContextSlotIndex(
+              scope_info, isolate_->factory()->this_string(), &mode, &location,
+              &init_flag, &maybe_assigned_flag) >= 0) {
+        return target;
+      }
+      receiver = handle(frame_->receiver(), isolate_);
+      break;
+    }
+    case MODULE_SCOPE:
+      receiver = isolate_->factory()->undefined_value();
+      break;
+    case SCRIPT_SCOPE:
+      receiver = handle(function->global_proxy(), isolate_);
+      break;
+    default:
+      // For eval code, arrow functions, and the like, there's no "this" binding
+      // to materialize.
+      return target;
+  }
+
+  return isolate_->factory()->NewCatchContext(
+      function, target, isolate_->factory()->this_string(), receiver);
+}
+
+}  // namespace internal
+}  // namespace v8