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From: John Maddock (jz.maddock_at_[hidden])
Date: 2021-08-04 18:26:29

On 04/08/2021 19:05, Robert Ramey via Boost wrote:
> On 8/3/21 4:29 PM, Robert Ramey via Boost wrote:
>> Any chance of seeing a feature macro for HAS_IS_CONSTANT_EVALUATED
>> appearing in Boost.Config any time soon?
> I guess it's not really necessary as std::is_constant_evaluated is
> slated for C++20.  And it includes a corresponding feature macro so it
> shouldn't be necessary for boost.config to include this functionality.
> I might have preferred the "unified" model of using boost.config for
> all these but I guess the easiest is just to role with the times.

Actually there is a roll for Boost.Config here:
std::is_constant_evaluated is valid in C++20 mode only, as is it's
feature detection macro.  However, the underlying compiler intrinsic
works just fine all the way back to C++11 mode as long as the compiler
has implemented it.

Multiprecision has the logic for this already:
albeit somewhat complexified because it uses __builtin_constant_p to
approximate std::is_constant_evaluated on older gcc versions.


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