Provide a counter for thrown JavaScript errors per context

src/factory.cc

 // Copyright 2014 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.
 
 #include "src/factory.h"
 
 #include "src/allocation-site-scopes.h"
 #include "src/base/bits.h"
 #include "src/bootstrapper.h"
 #include "src/conversions.h"
@@ skipping 708 matching lines @@
   return symbol;
 }
 
 
 Handle<Context> Factory::NewNativeContext() {
   Handle<FixedArray> array =
       NewFixedArray(Context::NATIVE_CONTEXT_SLOTS, TENURED);
   array->set_map_no_write_barrier(*native_context_map());
   Handle<Context> context = Handle<Context>::cast(array);
   context->set_js_array_maps(*undefined_value());
+  // Initialize with -1 because the value is incremented once
+  // during the build. This means the value is correctly initialized to
+  // 0 afterwards.
+  context->set_errors_thrown(Smi::FromInt(-1));

[Yang, 2015/11/02 05:48:57]

This seems somewhat brittle.

Could we move this line to bootstrapper.cc Genesis::Genesis, right after this:

isolate->counters()->contexts_created_from_scratch()->Increment();

https://code.google.com/p/chromium/codesearch#chromium/src/v8/src/bootstrappe...

[Michael Hablich, 2015/11/04 10:58:08]

Thanks for the remark. I left the initialization in factory.cc because it should
still create a valid Context. Additionally I re-initialize the the counter when
a context is loaded from the snapshot.

   DCHECK(context->IsNativeContext());
   return context;
 }
 
 
 Handle<Context> Factory::NewScriptContext(Handle<JSFunction> function,
                                           Handle<ScopeInfo> scope_info) {
   Handle<FixedArray> array =
       NewFixedArray(scope_info->ContextLength(), TENURED);
   array->set_map_no_write_barrier(*script_context_map());
@@ skipping 1650 matching lines @@
 }
 
 
 Handle<Object> Factory::ToBoolean(bool value) {
   return value ? true_value() : false_value();
 }
 
 
 }  // namespace internal
 }  // namespace v8