Emil Dotchevski wrote:
I apologize if this has been discussed before, but this message caught my attention and I decided to ask: why do you need any statics/globals for the serialization?
The static instantiations are used for a couple of things: a) maintaining table which is used to convert between different pointers to different types of objects at runtime - with or without RTTI existing. See void_cast ... b) To hold a constant string type "export" key as RTTI systems don't provide a portable one. c) To hold pointers to serialization functions for derived pointers. d) To guarentee instantiation of serialization functions not otherwise explicitly referred to. For more information - feel free to preuse the code.
I understand that you need global class registration to handle the case of reading a base pointer when the stream contains derived object, but when you serialize data you just assume that all classes have been registered ahead of time.
Not necessarily. The export functionality eliminates the requirement to explicitly register all derived types. Its original implementation initialized the type table upon first usage - the current one intializes the type table on start-up. This one of the changes I've been referring to in my belief that the situation may no longer exist.
Because you don't need mutable access to the class registration table, you don't have thread safety problems.
Iff and only iff you can get everthing initialize at pre-main time or upon DLL loading. Which has been exactly the problem up until now.
The other piece of data that I can think of is the table that tracks which objects have already been serialized so that when you serialize a second pointer that points to the same object you don't serialize the object again, however this table has to be per-stream because I may have multiple opened streams that I'm reading from. Assuming you don't access the same stream from multiple threads, I see no thread safety problems here either.
This is correct - there are no theading problems associated with tracking. Robert Ramey