[GSoC] __enable_shared_from_this_helper

[Jonathan Wakely]

On 30/04/15 10:41 -0700, Tim Shen wrote:
>This is why I was asking "still as usable". This feature actually
>requires more from the user, since standard didn't specify more.
>
>Anyway, we don't need to worry about this for now.

No, we don't have to worry about it ever. Period.

Allocators that only support allocating some types cannot be used in
arbitrary places in the library. That is already true for all the
node-based containers and for std::allocate_shared and lots of other
places that rely on rebinding allocators.

We do not have to (and *cannot*) support allocators that can't be
rebound to arbitrary types. That's not a problem that needs to be
solved!