Initialize pre-allocated fields of JSObject with undefined.

test/mjsunit/regress/regress-94873.js

+// Copyright 2011 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
+//       with the distribution.
+//     * Neither the name of Google Inc. nor the names of its
+//       contributors may be used to endorse or promote products derived
+//       from this software without specific prior written permission.
+//
+// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+// A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+// OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+// SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+// LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+// DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+// THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+// (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+// OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+
+// Flags: --expose-debug-as debug
+// Get the Debug object exposed from the debug context global object.
+Debug = debug.Debug;
+
+function sendCommand(state, cmd) {
+  // Get the debug command processor in paused state.
+  var dcp = state.debugCommandProcessor(false);
+  var request = JSON.stringify(cmd);
+  var response = dcp.processDebugJSONRequest(request);
+  return JSON.parse(response);
+}
+
+function listener(event, exec_state, event_data, data) {
+  try {
+    if (event == Debug.DebugEvent.Break) {
+      var line = event_data.sourceLineText();
+      print('break: ' + line);
+
+      var frame = sendCommand(exec_state, {
+        seq: 0,
+        type: "request",
+        command: "frame"
+      });
+
+      sendCommand(exec_state, {
+        seq: 0,
+        type: "request",
+        command: "evaluate",
+        arguments: {
+          expression: "obj.x.toString()",
+          additional_context: [{
+            name: "obj",
+            handle: frame.body.receiver.ref
+          }]
+        }
+      });
+    }
+  } catch (e) {
+    print(e);
+  }
+}
+
+Debug.setListener(listener);
+
+function a(x, y) {
+  this.x = x;
+  this.y = y;
+}
+
+Debug.setBreakPoint(a, 0, 0);
+new a(1, 2);