<version> provides __cpp_* feature-test macros (C++20) that tell you which C++ features are available in your compiler and standard library. For example, __cpp_concepts is defined if C++20 concepts are supported.

Use these in preprocessor conditionals to enable features selectively.

This example uses feature-test macros to conditionally report whether C++20 concepts and ranges are supported by the compiler.

// compile: g++ -std=c++20 -o versionexample versionexample.cpp
// run: ./versionexample
// description: check for C++ features
 
#include <version>
#include <iostream>
 
int main() {
#ifdef __cpp_concepts
    std::cout << "concepts supported\n";
#endif
 
#ifdef __cpp_ranges
    std::cout << "ranges supported\n";
#endif
 
    return 0;
}