Predefined macros for rvalue reference support?

[Peter Dimov]

David Fang wrote:
>>>> Can someone please tell me how a library can detect whether the
>>>> compiler supports rvalue references? I'm trying to enable move
>>>> support for boost::shared_ptr. Thanks.
>>>
>>> Hi,
>>> Do you mean at configure-time?
>>
>> No, I need a compile time check. The Boost config system is not
>> configure-based; it relies on the predefined preprocessor macros.
>
> You mean something like a template metaprogramming test or trait?  one
> that doesn't use the rvalue-reference syntax but can still distinguish
> between having and not having it?

No, I'm looking for a combination of predefined preprocessor macros that 
indicates that the compiler is in a mode where it recognizes &&. Something 
like

#ifdef __RVALUE_REFERENCE

or

#ifdef __GXX_EXPERIMENTAL_CXX0X__

or possibly

#if defined( __GXX_EXPERIMENTAL_CXX0X__ ) && !defined( __STRICT_ANSI__ )