Re: is_constant_evaluated

From: John Maddock (jz.maddock_at_[hidden])
Date: 2021-08-07 07:13:42

On 07/08/2021 05:46, Robert Ramey via Boost wrote:
> 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.

Yes, just give me a few days I'm tied up right now, John.

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