I have an Enum
Update update
refl->SetEnum (msg, fd , ??? );
message_desc->FindEnumTypeByName(s)->FindValueByNumber(update)
UpdateType
UpdateType::CONFIRM
CONFIRM
....
....
All you need in the third argument is EnumValueDescriptor*.
Also as you can see you have passed FieldDescriptor in the second argument. So just use FieldDesciptor::enum_type() to get EnumDescriptor* and then use EnumDescriptor::Value() to get EnumValueDescriptor.