So there are actually two main issues that need to be taken care of: - 1. dlls I think a good solution would be to add a new class, e.g. as Andrey Semashev proposed 'local_any', that derives from the current version of any. The normal version could be used for inter dll passing, the new version when the user can assure that a local_any instance won't be passed between dlls. Conversion could be provided from local_any to any. - 2. thread safety In c++03, variables defined at namespace scope are not necessarily initialized before main(), so there could be data races for the previous_id in next_id() in multi threaded applications. One simple way out would be to lock the variabe when used, but this would add the dependency on a threading library (does boost provide locking header only or does it need building?). It would be interesting to know, what c++11 says about the initialization of static data members. If it prohibits more than one initialization at a time or requires single threaded initialization before main() , locking will not be needed. -- Empfehlen Sie GMX DSL Ihren Freunden und Bekannten und wir belohnen Sie mit bis zu 50,- Euro! https://freundschaftswerbung.gmx.de