On 30.04.2012, at 18:51, Mathias Gaunard wrote:
On 29/04/12 03:16, Ahmed Charles wrote:
The downside of having it be a base class is that classes can now be marked final, which means they can't be used as base classes. This approach was used by libc++ for implementing the same optimization that STL mentions VC's STL implements, but I think they end up falling back to storing it if it's empty and final.
I suppose what we really want is static if. :)
Everything you could do with static if you can already do without, just with more verbose syntax.
In this particular case, however, I don't see how any if-like technique would help. I cannot think of a method to tell whether a type is empty without inheriting from it.
std::is_empty, of course. The implementation is up to the standard library - Clang provides an __is_empty trait intrinsic since we discovered the final class problem of the classic library implementation. Sebastian