Should compilers take advantage (abuse) of the new UDA syntax that has been accepted?

[Peter Alexander]

On Tuesday, 18 December 2012 at 16:43:53 UTC, Peter Alexander 
wrote:
> On Tuesday, 18 December 2012 at 15:19:58 UTC, Iain Buclaw wrote:
>> Should we take this as an opportunity for other compiler 
>> maintainers to implement their own compiler-specific 
>> predefined attributes?
>
> Please, no!

Before anyone says "that would never happen", consider that C++11 
was forced to use 'decltype' instead of the more natual 'typeof' 
because GCC already added 'typeof' as an extension. The same 
thing happened with the containers. GCC added stdext::hash_map as 
an extension, so C++11 had to use the ugly std::unordered_map 
(yep, even the different namespace didn't help).