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

[deadalnix]

On Tuesday, 18 December 2012 at 16:47:37 UTC, Peter Alexander 
wrote:
> 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).

Can you explain why it was an issue in the unordered_map case ? 
Because of using ?

I think this should be advertised that such a feature is in some 
GDC's specific module, and that it can clash with any library 
symbol at any time, as it is not a standardized feature of the 
language.