On Fri, Nov 26, 2021 at 12:29:25PM +0000, Jonathan Wakely via Gcc-patches wrote:
> + // Internal version of std::is_constant_evaluated() for C++11.
> + // This can be used without checking if the compiler supports the built-in.
> + constexpr inline bool
> + __is_constant_evaluated() noexcept
> + {
When you have such a nice one spot, shouldn't it:
#if __cpp_if_consteval >= 202106L
if consteval
{
return true;
}
else
{
return false;
}
#elif __has_builtin(__builtin_is_constant_evaluated)
...
Theoretically not all compilers need to support the builtin and in C++23
mode if consteval should be slightly more efficient.
One disadvantage of std::__is_constant_evaluated() is that Marek's
warning for if constexpr (std::is_constant_evaluated()) will not trigger
if __is_constant_evaluated() is used instead. But I'd hope testsuite
coverage would discover it quickly if such bug would appear...
Jakub
