Issue 2399 part 1: In debugger allow modifying local variable values

src/runtime.cc

 // Copyright 2012 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 10788 matching lines @@
                       NONE,
                       kNonStrictMode),
           Handle<JSObject>());
     }
   }
 
   return closure_scope;
 }
 
 
+// This method copies structure of MaterializeClosure method above.
+// TODO(code review): alternative approach is to generalize MaterializeClosure
+//     method so that it merely iterates properties, and a visitor
+//     materizalises or changes their values.
+//     But it would make code more complicated.
+static bool SetClosureVariableValue(Isolate* isolate, Handle<Context> context,

[Yang, 2012/11/27 16:46:23]

One argument per line please.

[Peter Rybin, 2012/11/27 18:24:28]

Done.

+                                    Handle<String> variable_name,
+                                    Handle<Object> new_value) {
+  ASSERT(context->IsFunctionContext());
+
+  Handle<SharedFunctionInfo> shared(context->closure()->shared());
+  Handle<ScopeInfo> scope_info(shared->scope_info());
+
+  // Context locals to the context extension.
+  for (int i = 0; i < scope_info->ContextLocalCount(); i++) {
+    Handle<String> next_name(scope_info->ContextLocalName(i));
+    if (variable_name->Equals(*next_name)) {
+      VariableMode mode;
+      InitializationFlag init_flag;
+      int context_index =
+          scope_info->ContextSlotIndex(*next_name, &mode, &init_flag);
+      if (context_index < 0) {
+        return false;
+      }
+      context->set(context_index, *new_value);
+      return true;
+    }
+  }
+
+  // Properties from the function context extension. This will
+  // be variables introduced by eval.
+  if (context->has_extension()) {
+    Handle<JSObject> ext(JSObject::cast(context->extension()));
+    bool threw = false;
+    Handle<FixedArray> keys =
+        GetKeysInFixedArrayFor(ext, INCLUDE_PROTOS, &threw);
+    if (threw) return false;
+
+    for (int i = 0; i < keys->length(); i++) {

[Yang, 2012/11/27 16:46:23]

Instead of iterating over all the keys, wouldn't it be possible to use
JSReceiver::HasProperty to check whether the property exists, and then set the
property using SetProperty?

[Peter Rybin, 2012/11/27 21:36:13]

Done.

+      // Names of variables introduced by eval are strings.
+      ASSERT(keys->get(i)->IsString());
+      Handle<String> key(String::cast(keys->get(i)));
+      if (key->Equals(*variable_name)) {
+        // We don't expect this to do anything except replacing property value.
+        // TODO(code review): should we do it more accurately?
+        SetProperty(ext,
+                    key,
+                    new_value,
+                    NONE,
+                    kNonStrictMode);
+        return true;
+      }
+    }
+  }
+
+  return false;
+}
+
+
 // Create a plain JSObject which materializes the scope for the specified
 // catch context.
 static Handle<JSObject> MaterializeCatchScope(Isolate* isolate,
                                               Handle<Context> context) {
   ASSERT(context->IsCatchContext());
   Handle<String> name(String::cast(context->extension()));
   Handle<Object> thrown_object(context->get(Context::THROWN_OBJECT_INDEX));
   Handle<JSObject> catch_scope =
       isolate->factory()->NewJSObject(isolate->object_function());
   RETURN_IF_EMPTY_HANDLE_VALUE(
@@ skipping 255 matching lines @@
         return MaterializeClosure(isolate_, CurrentContext());
       case ScopeIterator::ScopeTypeBlock:
         return MaterializeBlockScope(isolate_, CurrentContext());
       case ScopeIterator::ScopeTypeModule:
         return MaterializeModuleScope(isolate_, CurrentContext());
     }
     UNREACHABLE();
     return Handle<JSObject>();
   }
 
+  bool SetVariableValue(Handle<String> variable_name,
+                        Handle<Object> new_value) {
+    ASSERT(!failed_);
+    switch (Type()) {
+      case ScopeIterator::ScopeTypeGlobal:
+        break;
+      case ScopeIterator::ScopeTypeLocal:
+        // TODO(2399): implement.
+        break;
+      case ScopeIterator::ScopeTypeWith:
+        break;
+      case ScopeIterator::ScopeTypeCatch:
+        // TODO(2399): implement.
+        break;
+      case ScopeIterator::ScopeTypeClosure:
+        return SetClosureVariableValue(isolate_, CurrentContext(),
+            variable_name, new_value);
+      case ScopeIterator::ScopeTypeBlock:
+        // TODO(2399): should we implement it?
+        break;
+      case ScopeIterator::ScopeTypeModule:
+        // TODO(2399): should we implement it?
+        break;
+    }
+    return false;
+  }
+
   Handle<ScopeInfo> CurrentScopeInfo() {
     ASSERT(!failed_);
     if (!nested_scope_chain_.is_empty()) {
       return nested_scope_chain_.last();
     } else if (context_->IsBlockContext()) {
       return Handle<ScopeInfo>(ScopeInfo::cast(context_->extension()));
     } else if (context_->IsFunctionContext()) {
       return Handle<ScopeInfo>(context_->closure()->shared()->scope_info());
     }
     return Handle<ScopeInfo>::null();
@@ skipping 219 matching lines @@
     n++;
   }
   if (it.Done()) {
     return isolate->heap()->undefined_value();
   }
 
   return MaterializeScopeDetails(isolate, &it);
 }
 
 
+static bool SetScopeVariableValue(ScopeIterator* it, int index,
+                                  Handle<String> variable_name,
+                                  Handle<Object> new_value) {
+  int n = 0;
+  for (; !it->Done() && n < index; it->Next()) {
+    n++;
+  }
+  if (it->Done()) {
+    return false;
+  }
+  return it->SetVariableValue(variable_name, new_value);
+}
+
+
+// Change variable value in closure or local scope
+// args[0]: number or JsFunction: break id or function
+// args[1]: number: frame index (when arg[0] is break id)
+// args[2]: number: inlined frame index (when arg[0] is break id)
+// args[3]: number: scope index
+// args[4]: string: variable name
+// args[5]: object: new value
+//
+// Return true if success and false otherwise
+RUNTIME_FUNCTION(MaybeObject*, Runtime_SetScopeVariableValue) {
+  HandleScope scope(isolate);
+  ASSERT(args.length() == 6);
+
+  // Check arguments.
+  CONVERT_NUMBER_CHECKED(int, index, Int32, args[3]);
+  CONVERT_ARG_HANDLE_CHECKED(String, variable_name, 4);
+  Handle<Object> new_value = args.at<Object>(5);
+
+  bool res;
+  if (args[0]->IsNumber()) {
+    Object* check;
+    { MaybeObject* maybe_check = Runtime_CheckExecutionState(
+        RUNTIME_ARGUMENTS(isolate, args));
+      if (!maybe_check->ToObject(&check)) return maybe_check;
+    }
+    CONVERT_SMI_ARG_CHECKED(wrapped_id, 1);
+    CONVERT_NUMBER_CHECKED(int, inlined_jsframe_index, Int32, args[2]);
+
+    // Get the frame where the debugging is performed.
+    StackFrame::Id id = UnwrapFrameId(wrapped_id);
+    JavaScriptFrameIterator frame_it(isolate, id);
+    JavaScriptFrame* frame = frame_it.frame();
+
+    ScopeIterator it(isolate, frame, inlined_jsframe_index);
+    res = SetScopeVariableValue(&it, index, variable_name, new_value);
+  } else {
+    CONVERT_ARG_HANDLE_CHECKED(JSFunction, fun, 0);
+    ScopeIterator it(isolate, fun);
+    res = SetScopeVariableValue(&it, index, variable_name, new_value);
+  }
+
+  return isolate->heap()->ToBoolean(res);
+}
+
+
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DebugPrintScopes) {
   HandleScope scope(isolate);
   ASSERT(args.length() == 0);
 
 #ifdef DEBUG
   // Print the scopes for the top frame.
   StackFrameLocator locator;
   JavaScriptFrame* frame = locator.FindJavaScriptFrame(0);
   for (ScopeIterator it(isolate, frame, 0);
        !it.Done();
@@ skipping 1984 matching lines @@
     // Handle last resort GC and make sure to allow future allocations
     // to grow the heap without causing GCs (if possible).
     isolate->counters()->gc_last_resort_from_js()->Increment();
     isolate->heap()->CollectAllGarbage(Heap::kNoGCFlags,
                                        "Runtime::PerformGC");
   }
 }
 
 
 } }  // namespace v8::internal