[Bug libstdc++/54468] type trait is_unsigned<...>::value for C++11 enum class with underlying unsigned type not true

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54468

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler at
                   |                            |googlemail dot com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2012-09-04 15:30:53 UTC ---
(In reply to comment #0)
> The is_unsigned<> type trait is not detecting the underlying signedness of a
> C++11 enum class or enum.

This is what the standard requires. The definition of is_unsigned is specified
as:

is_arithmetic<T>::value && T(-1) < T(0)

Since enum types are no arithmetic types, the traits must return false for
either of these.