Allow debugger evaluate expressions to mute local variables

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 12354 matching lines @@
 // Evaluate a piece of JavaScript in the context of a stack frame for
 // debugging.  This is done by creating a new context which in its extension
 // part has all the parameters and locals of the function on the stack frame
 // as well as a materialized arguments object.  As this context replaces
 // the context of the function on the stack frame a new (empty) function
 // is created as well to be used as the closure for the context.
 // This closure as replacements for the one on the stack frame presenting
 // the same view of the values of parameters and local variables as if the
 // piece of JavaScript was evaluated at the point where the function on the
 // stack frame is currently stopped when we compile and run the (direct) eval.
+// Returns array of
+// #0: evaluate result
+// #1: local variables scope materizalized as object before evaluation
+// #2: local variables scope materizalized as object after evaluation
+// Since user expression only reaches (and modifies) copies of local variables,
+// those copies are returned to the caller to allow it track the changes and

[Yang, 2013/06/25 11:15:01]

do you mean "... to allow tracking the changes..." ?

[Peter Rybin, 2013/06/25 12:22:41]

Yes. Done.

+// manually update the actual variables.
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DebugEvaluate) {
   HandleScope scope(isolate);
 
   // Check the execution state and decode arguments frame and source to be
   // evaluated.
   ASSERT(args.length() == 6);
   Object* check_result;
   { MaybeObject* maybe_result = Runtime_CheckExecutionState(
       RUNTIME_ARGUMENTS(isolate, args));
     if (!maybe_result->ToObject(&check_result)) return maybe_result;
@@ skipping 79 matching lines @@
                                         frame,
                                         inlined_jsframe_index);
   if (context.is_null()) {
     ASSERT(isolate->has_pending_exception());
     MaybeObject* exception = isolate->pending_exception();
     isolate->clear_pending_exception();
     return exception;
   }
 
   Handle<Object> receiver(frame->receiver(), isolate);
-  return DebugEvaluate(isolate, context, context_extension, receiver, source);
+  Object* evaluate_result_object;
+  { MaybeObject* maybe_result =
+    DebugEvaluate(isolate, context, context_extension, receiver, source);
+    if (!maybe_result->ToObject(&evaluate_result_object)) return maybe_result;
+  }
+  Handle<Object> evaluate_result(evaluate_result_object, isolate);
+
+  Handle<JSObject> local_scope_after = MaterializeLocalScopeWithFrameInspector(
+      isolate, frame, &frame_inspector);
+
+  Handle<FixedArray> resultArray =
+      isolate->factory()->NewFixedArray(3);
+  resultArray->set(0, *evaluate_result);
+  resultArray->set(2, *local_scope);
+  resultArray->set(1, *local_scope_after);
+
+  return *(isolate->factory()->NewJSArrayWithElements(resultArray));
 }
 
 
 RUNTIME_FUNCTION(MaybeObject*, Runtime_DebugEvaluateGlobal) {
   HandleScope scope(isolate);
 
   // Check the execution state and decode arguments frame and source to be
   // evaluated.
   ASSERT(args.length() == 4);
   Object* check_result;
@@ skipping 1362 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