Hi,

AFAICS the standard is unclear whether a custom
allocater ALLOC<T> that shall be used with any
stdc++ library (-> 'stateless', pointer is T*)
shall allow things like ...

   ALLOC<incomplete_type>::pointer p;

(typically coming from ...
ALLOC<known>::rebind<incomplete_type>::other::pointer)

Currently w.r.t. rebind<U>, 20.1.5,tbl31 says "U ... any
type". Maybe "U ... any complete type" ?

The problem is that even when ALLOC<T>::pointer is T* in
any case, ALLOC<T> might not 'compile' for incomplete T
(e.g. struct ALLOC<T>: IMPL<sizeof(T)> {...}).

The answer then decides whether one can build linked
nodes containing ALLOC<still_incomplete_node>::pointer.

One workaround could be requiring ...

ALLOC<known>::rebind<incomplete_type>::pointer
                                    ( ^ NO "::other")

OTOH a library that doesnt want to support other ::pointer's
than T* could easily use "still_incomplete_node*" instead of
ALLOC<known>::rebind<still_incomplete_node>::pointer.

BTW, for advanced allocators where alloc<T>::pointer really
needs a complete T, the design of nodes containing
alloc<node>::pointer will be interesting.


Thanks,
Markus.

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