[debugger] do not expose temporary variables introduced by the parser.

R=bmeurer@chromium.org, kozyatinskiy@chromium.org
BUG=chromium:582048
LOG=N

Review URL: https://codereview.chromium.org/1916343002

Cr-Commit-Position: refs/heads/master@{#35805}

src/ast/scopeinfo.cc

@@ -438,16 +438,13 @@ MaybeAssignedFlag ScopeInfo::ContextLocalMaybeAssignedFlag(int var) {
   return ContextLocalMaybeAssignedFlag::decode(value);
 }
 
-
-bool ScopeInfo::LocalIsSynthetic(int var) {
-  DCHECK(0 <= var && var < LocalCount());
+bool ScopeInfo::VariableIsSynthetic(String* name) {
   // There's currently no flag stored on the ScopeInfo to indicate that a
   // variable is a compiler-introduced temporary. However, to avoid conflict
   // with user declarations, the current temporaries like .generator_object and
   // .result start with a dot, so we can use that as a flag. It's a hack!
-  Handle<String> name(LocalName(var));
-  return (name->length() > 0 && name->Get(0) == '.') ||
-         name->Equals(*GetIsolate()->factory()->this_string());
+  return name->length() == 0 || name->Get(0) == '.' ||
+         name->Equals(name->GetHeap()->this_string());
 }
 
 

src/debug/debug-frames.cc

@@ -116,6 +116,7 @@ void FrameInspector::MaterializeStackLocals(Handle<JSObject> target,
     // TODO(yangguo): check whether this is necessary, now that we materialize
     //                context locals as well.
     Handle<String> name(scope_info->ParameterName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     if (ParameterIsShadowedByContextLocal(scope_info, name)) continue;
 
     Handle<Object> value =
@@ -129,8 +130,8 @@ void FrameInspector::MaterializeStackLocals(Handle<JSObject> target,
 
   // Second fill all stack locals.
   for (int i = 0; i < scope_info->StackLocalCount(); ++i) {
-    if (scope_info->LocalIsSynthetic(i)) continue;
     Handle<String> name(scope_info->StackLocalName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     Handle<Object> value = GetExpression(scope_info->StackLocalIndex(i));
     // TODO(yangguo): We convert optimized out values to {undefined} when they
     // are passed to the debugger. Eventually we should handle them somehow.
@@ -162,6 +163,7 @@ void FrameInspector::UpdateStackLocalsFromMaterializedObject(
   for (int i = 0; i < scope_info->ParameterCount(); ++i) {
     // Shadowed parameters were not materialized.
     Handle<String> name(scope_info->ParameterName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     if (ParameterIsShadowedByContextLocal(scope_info, name)) continue;
 
     DCHECK(!frame_->GetParameter(i)->IsTheHole());
@@ -172,13 +174,12 @@ void FrameInspector::UpdateStackLocalsFromMaterializedObject(
 
   // Stack locals.
   for (int i = 0; i < scope_info->StackLocalCount(); ++i) {
-    if (scope_info->LocalIsSynthetic(i)) continue;
+    Handle<String> name(scope_info->StackLocalName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     int index = scope_info->StackLocalIndex(i);
     if (frame_->GetExpression(index)->IsTheHole()) continue;
     Handle<Object> value =
-        Object::GetPropertyOrElement(
-            target, handle(scope_info->StackLocalName(i), isolate_))
-            .ToHandleChecked();
+        Object::GetPropertyOrElement(target, name).ToHandleChecked();
     frame_->SetExpression(index, *value);
   }
 }

src/debug/debug-scopes.cc

@@ -801,19 +801,16 @@ void ScopeIterator::CopyContextLocalsToScopeObject(
   int local_count = scope_info->ContextLocalCount();
   if (local_count == 0) return;
   // Fill all context locals to the context extension.
-  int first_context_var = scope_info->StackLocalCount();
-  int start = scope_info->ContextLocalNameEntriesIndex();
   for (int i = 0; i < local_count; ++i) {
-    if (scope_info->LocalIsSynthetic(first_context_var + i)) continue;
+    Handle<String> name(scope_info->ContextLocalName(i));
+    if (ScopeInfo::VariableIsSynthetic(*name)) continue;
     int context_index = Context::MIN_CONTEXT_SLOTS + i;
     Handle<Object> value = Handle<Object>(context->get(context_index), isolate);
     // Reflect variables under TDZ as undefined in scope object.
     if (value->IsTheHole()) continue;
     // This should always succeed.
     // TODO(verwaest): Use AddDataProperty instead.
-    JSObject::SetOwnPropertyIgnoreAttributes(
-        scope_object, handle(String::cast(scope_info->get(i + start))), value,
-        NONE)
+    JSObject::SetOwnPropertyIgnoreAttributes(scope_object, name, value, NONE)
         .Check();
   }
 }

src/objects.h

@@ -4194,7 +4194,7 @@ class ScopeInfo : public FixedArray {
 
   // Return true if this local was introduced by the compiler, and should not be
   // exposed to the user in a debugger.
-  bool LocalIsSynthetic(int var);
+  static bool VariableIsSynthetic(String* name);
 
   // Lookup support for serialized scope info. Returns the
   // the stack slot index for a given slot name if the slot is

src/runtime/runtime-debug.cc

@@ -571,7 +571,9 @@ RUNTIME_FUNCTION(Runtime_GetFrameDetails) {
   for (int slot = 0; slot < scope_info->LocalCount(); ++slot) {
     // Hide compiler-introduced temporary variables, whether on the stack or on
     // the context.
-    if (scope_info->LocalIsSynthetic(slot)) local_count--;
+    if (ScopeInfo::VariableIsSynthetic(scope_info->LocalName(slot))) {
+      local_count--;
+    }
   }
 
   Handle<FixedArray> locals =
@@ -582,7 +584,7 @@ RUNTIME_FUNCTION(Runtime_GetFrameDetails) {
   int i = 0;
   for (; i < scope_info->StackLocalCount(); ++i) {
     // Use the value from the stack.
-    if (scope_info->LocalIsSynthetic(i)) continue;
+    if (ScopeInfo::VariableIsSynthetic(scope_info->LocalName(i))) continue;
     locals->set(local * 2, scope_info->LocalName(i));
     Handle<Object> value = frame_inspector.GetExpression(i);
     // TODO(yangguo): We convert optimized out values to {undefined} when they
@@ -596,8 +598,8 @@ RUNTIME_FUNCTION(Runtime_GetFrameDetails) {
     Handle<Context> context(
         Handle<Context>::cast(frame_inspector.GetContext())->closure_context());
     for (; i < scope_info->LocalCount(); ++i) {
-      if (scope_info->LocalIsSynthetic(i)) continue;
       Handle<String> name(scope_info->LocalName(i));
+      if (ScopeInfo::VariableIsSynthetic(*name)) continue;
       VariableMode mode;
       InitializationFlag init_flag;
       MaybeAssignedFlag maybe_assigned_flag;

test/mjsunit/debug-scopes.js

@@ -183,10 +183,8 @@ function CheckScopeContent(content, number, exec_state) {
   if (!scope.scopeObject().property('this').isUndefined()) {
     scope_size--;
   }
-  // Skip property with empty name.
-  if (!scope.scopeObject().property('').isUndefined()) {
-    scope_size--;
-  }
+  // Temporary variables introduced by the parser have not been materialized.
+  assertTrue(scope.scopeObject().property('').isUndefined());
 
   if (count != scope_size) {
     print('Names found in scope:');

test/mjsunit/es6/debug-blockscopes.js

@@ -148,10 +148,8 @@ function CheckScopeContent(content, number, exec_state) {
   if (!scope.scopeObject().property('arguments').isUndefined()) {
     scope_size--;
   }
-  // Skip property with empty name.
-  if (!scope.scopeObject().property('').isUndefined()) {
-    scope_size--;
-  }
+  // Temporary variables introduced by the parser have not been materialized.
+  assertTrue(scope.scopeObject().property('').isUndefined());
 
   if (count != scope_size) {
     print('Names found in scope:');

test/mjsunit/regress/regress-crbug-582048.js

+// Copyright 2016 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.
+
+// Flags: --expose-debug-as debug
+
+var Debug = debug.Debug;
+
+function listener(event, exec_state, event_data, data) {
+  if (event != Debug.DebugEvent.Break) return;
+  try {
+    var frame_count = exec_state.frameCount();
+    for (var i = 0; i < frame_count; i++) {
+      var frame = exec_state.frame(i);
+      var scope_count = frame.scopeCount();
+      for (var j = 0; j < scope_count; j++) {
+        var scope = frame.scope(j);
+        assertTrue(scope.scopeObject().property('').isUndefined());
+      }
+    }
+  } catch (e) {
+    print(e, e.stack);
+    exception = e;
+  }
+}
+
+Debug.setListener(listener);
+
+(function(a = 1) { debugger; })();
+
+Debug.setListener(null);