Introduce --zap-cpp-pointers (off by default)

test/cctest/test-debug.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 5952 matching lines @@
 
   int expected_frame_count = 4;
   int expected_line_number[] = {1, 4, 7, 12};
 
   i::Handle<i::Object> compiled_script = v8::Utils::OpenHandle(*inline_script);
   i::Handle<i::Script> source_script = i::Handle<i::Script>(i::Script::cast(
       i::JSFunction::cast(*compiled_script)->shared()->script()));
 
   int break_id = CcTest::i_isolate()->debug()->break_id();
   char script[128];
+  memset(script, 0, sizeof(script));
   i::Vector<char> script_vector(script, sizeof(script));
   SNPrintF(script_vector, "%%GetFrameCount(%d)", break_id);
   v8::Local<v8::Value> result = CompileRun(script);
 
   int frame_count = result->Int32Value(context).FromJust();
   CHECK_EQ(expected_frame_count, frame_count);
 
   for (int i = 0; i < frame_count; i++) {
     // The 6. element in the returned array of GetFrameDetails contains the
     // source position of that frame.
@@ skipping 748 matching lines @@
   // itself contains additional sanity checks.
   for (i::Handle<i::JSFunction> fun : list) {
     bool failed = false;
     {
       i::NoSideEffectScope scope(isolate, true);
       failed = !isolate->debug()->PerformSideEffectCheck(fun);
     }
     if (failed) isolate->clear_pending_exception();
   }
 }