I assume you're asking about a check for constness, like __is_constexpr() in Linux kernel. Starting with C11, it's possible to implement it without any non-sta

I assume you're asking about a check for constness, like __is_constexpr() in Linux kernel. Starting with C11, it's possible to implement it without any non-standard extensions: https://stackoverflow.com/a/49480926 https://stackoverflow.com/a/49480926