while the custom allocators let you put std::containers in shared memory they are still not very useful since they can only be used by the process that put them there - other processes will (potentially) see the shared memory at a different address and all the pointers will be wrong
Isn't this *exactly* what the allocator's nested ::pointer type is for?
Maybe, but it's use would be pretty limited. The std lib is entitled to assume that: "The typedef members pointer, const_pointer, size_type, and difference_type are required to be T*,T const*, size_t, and ptrdiff_t, respectively" So I wouldn't be able to use any std lib containers within regex if we were to allow the ::pointer type to be useful :-( And boost::shared_ptr, while allocating it's memory via an allocator is completely agnostic about it's type, so I couldn't use any smart pointer classes either :-( So... all I would need to do is reimplement the std lib, and shared_ptr etc... or maybe not! Which is not to say that having an allocator for other purposes isn't worthwhile, Cheers, John.