Using C++ preprocessor to detect C++ standard

cpp_version_macro.cpp

#include <cstdio>

int main()  {
    // Also see https://en.cppreference.com/w/cpp/feature_test
    // and https://en.cppreference.com/w/User:D41D8CD98F/feature_testing_macros
#ifndef __cplusplus
    #error C++ is required
#elif __cplusplus < 199711L
    puts("before C++98?!?");
#elif __cplusplus < 201103L
    puts("C++98");
#elif __cplusplus < 201402L
    puts("C++11");
#elif __cplusplus < 201703L
    puts("C++17");
#elif __cplusplus < 202002L
    puts("C++17");
#elif __cplusplus < 202100L
    puts("C++20");
#else
    puts("C++23 or newer");
#endif

    return 0;
}