Is it possible to avoid overhead while using boost_any?

Question

I'd like to use boost::any as a universal type to store in a container and to pass to different functions. But inside these functions I always know the real type, so in runtime I don't need any type safety checks and the imposed overhead, static_cast is enough.

The ideal solution would be to use something like boost::polymorphic_downcast, but as I can see it can't be applied in this case.

Should I just write my own wrapper for void* or is there another option?

If you know the types at compile time anyway, why need `boost::any`? Can't you use a struct containing all the types you need an put that in a container? — Tony The Lion, May 22 '13 at 14:24
@TonyTheLion: Whouldn't that be terribly memory-inefficient? — Armen Tsirunyan, May 22 '13 at 14:26
If it's really true that `any` is the right type *and* you always know the actual type, then you could make a container of void pointers... — Kerrek SB, May 22 '13 at 14:28
where are you loosing type of your container? Maybe you should not do that? — kassak, May 22 '13 at 14:31
Because it's choosen in runtime what type is needed and what is not, and I also would prefer not to change the code for this global container in case I would need another type. — lizarisk, May 22 '13 at 14:32
Also if you will put your container into `boost::any` it will devrease overhead — kassak, May 22 '13 at 14:34
@ArmenTsirunyan I suppose that depends on what types you have and how you arrange them in your struct. — Tony The Lion, May 22 '13 at 14:36

score 1 · Answer 1 · answered May 22 '13 at 14:53

You may use shared_ptr<void> or unique_ptr with static_cast to replace boost::any, shared_ptr<void> has several advantage over raw void* pointer like:

automatically delete its storage
can referenced by multiple object in your code(may be you don't need this)

But of course in this case you need more memory for every pointer(for reference counting and deleter).

if sharing is not good for you and your object will only owned in container you may also use unique_ptr<void>.

Is it possible to avoid overhead while using boost_any?

1 Answers1