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The main problem I had was that certain member variable weren't accessible. The STL collections don't have that issue so there was no problem.

Sorry if this is silly question, but why would you need an access to the counter? IMO we should be able to save/load shared_ptr without need to save it.

I checked the code (which was written some time ago) and the answer to that question isn't obvious to me. I do remember starting with the idea that it wouldn't be necessary to look beyond shared_ptr but I had to just keep adding on to make things work. The implementation of shared_ptr is A LOT more involved that one would guess. My implementation of shared_ptr implementation may not be the only or best one. It is pretty straight forward however in that it follows the chain of composition - which includes shared_count. Sorry I can't give a better answer. Robert Ramey