Re: use of type_traits

[Jonathan Wakely <cow at compsoc dot man dot ac dot uk>]

On Thu, Jan 27, 2005 at 12:36:43PM +0100, Paolo Carlini wrote:

> Benjamin Kosnik wrote:
> 
> >Sorry if this has been discussed already. 
> > 
> >
> You may find interesting this thread:
> 
>    http://gcc.gnu.org/ml/libstdc++/2004-07/msg00224.html

The non-polluting macros might be the best, long-term solution.

I've ruled out something like this, due to ODR violations:

    #ifdef _GLIBCXX_ADD_TR1_TO_STD
    namespace std { namespace tr1 {} }
    namespace __gnucxx_tr1 = std::tr1;
    namespace std {
    #else
    namespace __gnucxx { namespace tr1 {} }
    namespace __gnucxx_tr1 = __gnucxx::tr1;
    namespace __gnucxx {
    #endif
    namespace tr1 {
    // type traits definitions...
    } }

But how about always declaring the TR1 traits in our private namespace
and conditionally pulling them into std with a strong using?  If strong
using works properly (there are currently a couple of bugs IIRC) that
should do what we want, shouldn't it?

Alternatively, for a _really_ shoddy attempt, we could just declare them
in our namespace and use (non-strong) using decls to pull them into std.
That wouldn't be conforming, but it's only a TR so we aren't obliged to
be strictly conforming. Maybe.

jon

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