Re: is_constant_evaluated

From: Robert Ramey (ramey_at_[hidden])
Date: 2021-08-07 04:46:05

On 8/4/21 11:26 AM, John Maddock via Boost wrote:
> On 04/08/2021 19:05, Robert Ramey via Boost wrote:

> 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: 
> https://github.com/boostorg/multiprecision/blob/dd4d566055ff6eee6006f8f954efd3035bdf442a/include/boost/multiprecision/detail/number_base.hpp#L96-L132 
> albeit somewhat complexified because it uses __builtin_constant_p to 
> approximate std::is_constant_evaluated on older gcc versions.

This looks what I w was looking for.  Is there any chance to get this 
moved into Boost.Config ?  I think it would be even better than what I 
was looking for.

Robert Ramey
> 
> John.
> 
> 
>