Comment #1 on issue 398 by ernst.matthias: Overwriting function-valued
property of first ObjectTemplate instance gives "undefined" on clones
http://code.google.com/p/v8/issues/detail?id=398
The reproducer is even easier, it has nothing to do with templates:
v8::Handle<v8::Object> o = v8::Object::New();
o->Set(v8::String::New("method"),
v8::FunctionTemplate::New()->GetFunction());
o->Clone()->Set(v8::String::New("method"), v8::String::New("new value"));
cerr << *v8::String::AsciiValue(o->Get(v8::String::New("method"))) <<
endl;
I've tracked it down to JSObject::ConvertDescriptorToFieldAndMapTransition
which
overwrites the original CONSTANT_FUNCTION descriptor with a
MAP_TRANSITION . Objects
that share the same original map (only possible through Clone?) will see
their
function disappear.
I cannot judge what is the right fix. Maybe the MAP_TRANSITION should copy
the
function constant? Maybe a different type of Descriptor needs to be
inserted that
does so? Maybe Clone() cannot re-use the map if it contain a function
constants?
Maybe we cannot leave a MAP_TRANSITION when overriding a function constant.
Interestingly, function constants are only used if the property is new.
After that, a
CONSTANT_TRANSITION is left in the original map with the specific purpose
to trigger creation of fields for reasons I don't understand.
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