[SG10] Feature-testing for a TS

Jens Maurer Jens.Maurer at gmx.net
Wed Mar 25 23:07:27 CET 2015


On 03/25/2015 12:30 AM, Nelson, Clark wrote:
>> 	Should TSes use the macro spelling pattern
>>
>> 	  __cpp_experimental_whatever
>>
>> 	or
>>
>> 	  __cpp_whatever
>>
>> 	assuming that the value of the macro will change anyway when
>> a feature
>> 	moves from TS land to the standard proper?
> 
> The question is, when a feature from a TS is incorporated into the standard,
> will it be changed enough to effectively make it a different feature from
> what was in the TS? If not, the same macro name should be used; if so, it
> should be a different macro name.
> 
> Changing the macro's value is perfectly OK when only a minor tweak is made.
> 
> Is your principal concern about the TM TS? Is there an expectation that a
> feature-test macro will be added to it before it is finalized?

Yes, there's an NB comment for it.  (We made one.)

We'll go with __cpp_transactional_memory . I don't expect
large changes before going into the standard.

> All I can say about "experimental" language features is that it sure would
> be nice if we could get them right in the TS, so that, when (or if) they are
> incorporated into the standard, they don't have to be changed enough to be
> considered a different feature.

Ok.  That seems to be consistent with the TM approach.

Thanks,
Jens



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