Implement C++20 p1424 - 'constexpr' feature macro concerns.

Jonathan Wakely
Tue Aug 20 22:14:00 GMT 2019

On 16/08/19 22:39 -0400, Ed Smith-Rowland via libstdc++ wrote:
>The latest draft and I guess the above paper changed the macro names 
>for the C++20 constexpr lib featues.
>__cpp_lib_constexpr_algorithms ->__cpp_lib_constexpr.

The __cpp_lib_constexpr macro is (now?) for a different feature.

The proposed resolution for
is to keep the __cpp_lib_constexpr_algorithms name to indicate support
for what is currently described by __cpp_lib_constexpr_swap_algorithms
(and see for another issue
in this area).

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